Physics for the Cambridge iGCSE Syllabus
B. Murphy
Contents Topic Topic 1 Topic 2 Topic 3 Topic 4 Topic 5
Page Number
General Physics Past Paper Questions Thermal Physics Past Paper Questions Waves Past Paper Questions Electricity & Magnetism Past Paper Questions Atomic Physics Past Paper Questions
Appendix Syllabus
2 26 70 83 108 120 146 173 214 221 234
1
Topic 1: General Physics
1
Length •
Length is a distance measurement and its SI unit is the metre (m).
•
Length is usually measured with a rule, a tape or a trundle wheel.
•
Small lengths are measured with a micrometer or callipers where a greater precision is available.
•
In certain circumstances, average lengths can be found be measuring a number of distances together then dividing by the number of objects eg a ream of paper.
2
Time •
Time is usually measured with a stopclock. Human timing is not precise because of reaction times.
•
The SI unit for time is seconds (s).
•
For repeated events, an average time can be found by measuring a number of repeats then dividing by the number of cycles eg. a pendulum.
3 2
Speed •
Speed tells us how fast something is moving.
•
It is measured in m/s.
•
Average speed is calculated using:
Average Speed (m s) =
Distance moved (m) time taken (s)
4
Examples •
A sprinter runs 100m in 10s. Calculate his average speed.
•
A bird flies 60m in 5s. Calculate its average speed.
•
Pupils measured their times taken to travel different distances doing various exercises. Their results are recorded in the table. Complete the table. Exercise
Distance (m)
Time (s)
Running
70
12
Walking
10
35
Hopping
50
110
Speed (m/s)
5
Acceleration •
Acceleration tells us how quickly something is changing its speed.
•
It is measured in m/s2.
•
Acceleration is calculated using: Average Acceleration (m s 2 ) =
Change in speed ( m s ) time taken (s)
Example:
•
A motorbike goes from 10m/s to 35 m/s in 8s. Calculate his acceleration
6 3
Distance/time graphs •
A Distance/time graph is a way of representing motion. distance Acceleration stationary Constant speed (fast)
Constant speed (slow)
time
7
Calculations with distance/ time graphs •
Speed is given by the gradient of the distance/time graph.
8
Distance/time graph questions •
Describe the motion of the following bodies:
(a)
(b) d
(c) d
t
d
t
t
9 4
Distance/Time Graph questions • Calculate the speeds of the car and the bike below: Distance (m)
500 375
Car Bike
250 125 0 0
5
10
15
20
25
10
Time (s)
Speed/time graphs • A Speed/time graph is an alternative way of representing motion. speed Non-Uniform Acceleration Constant speed Rapid acceleration Gradual acceleration Stationary time
11
Calculations with speed/time graphs •
Acceleration is given by the gradient of the speed/ time graph.
•
Distance is given by the Area under the speed/time graph.
12 5
Speed/time graph questions Describe the motion of the following bodies:
• (a)
(b) v
(c) v
v
t
t
t
13
Speed/time calculation. •
(a) Find the acceleration of the bike in the first 10s.
•
(b) Find the distance moved by the bike in the first 20s. Motion of a bike
15.00
Speed (m/s)
11.25
7.50
3.75
0 0
5
10
15
20
14
time (s)
The Ticker-Timer
Ticker Tape Ticker Timer
• The ticker-timer runs at 50Hz. It puts 50 dots on the tape every second.
• If the tape moves quickly, the dots are widely spaced.
• If the tape moves slowly, the dots are close
15 6
Ticker Tape
Slow moving ticker-tape
Fast moving ticker-tape
16
Charts •
By cutting the tape into 5 space strips and arranging them side-by-side we can get a chart representing the motion.
•
Each strip will represent 0.1s of motion.
17
Typical Shapes of Charts
18 7
Calculations •
Since each strip represents 0.1s of motion, and we can measure the length of the strips in cm, we can use speed=distance/time to calculate the speeds.
19
Scalars and Vectors •
A SCALAR quantity has a size (Magnitude), but no direction.
•
Examples of scalar Quantities are temperature, time, energy and power.
•
A VECTOR quantity has both a magnitude and a direction. Vectors are often represented with an arrowed line. The direction of the arrow is the direction of the vector and the length of the line represents the size of the vector.
•
Examples of vectors are force, momentum and velocity.
F
20
2
1 Big Stone
Small Stone
Paper Tray
3 Small Stone
Paper
Coin
Vacuum Sand Bucket
Sand Bucket
21 8
Gravity •
•
•
Experiment 1
•
Both Stones Land at the same time.
•
Gravity makes them fall at the same rate.
Experiment 2
•
Stone landed first.
•
Air Resistance slowed down the paper tray.
Experiment 3
•
Both coin & paper land at the same time.
22
Weight and Mass •
Weight is a force. It tells us how heavy something is. It is measured in newtons (N). It changes depending upon the size of gravity. (Trip to the moon)
•
Mass tells us how much substance there is in an object. It is measured in kilograms (kg). It never changes.
•
On Earth we multiply mass by 10 to get weight.
23
Density •
Density tells us how compact the mass is in a material.
•
It is given by:
Density ( kg m 3 ) =
mass(kg) volume(m 3 )
or
Density ( g cm 3 ) =
mass(g) volume(cm 3 )
•Stick to one set of units. •Water has a density of 1000 kg/m3 or 1 g/cm3. •Materials with a smaller density than water will float, materials with a higher density than water will sink.
24 9
Density Calculation Complete the following table: Object
Density (kg/ m3)
A B
8000
C
2000
D
Mass (kg)
Volume (m3)
4000
2 4
1000 2000
4
a) Which object has the greatest mass? b) Which has the smallest volume? c) Which objects could be made of the same substance? d) Which object would float on water?
25
Irregular objects •
The volume of a liquid can be determined using a measuring cylinder.
•
The volume of irregular objects has to be found by displacement.
26
Hooke’s Law •
Hooke’s Law states that the extension in a spring is proportional to the load applied. load α extension or F = kx
The constant of proportionality is called the Spring Constant.
27 10
Extension/Force Graphs •
A graph can be plotted to show how Force varies with extension for a spring.
•
The graph shows proportionality up to a point called the ‘proportionality limit’.
•
With increased extension, the spring will reach a point at which it will not return to its original shape. This is called the elastic limit. The spring shows ‘plastic’ behaviour beyond here.
28
Load/Extension Graphs •
A graph can be plotted to show how extension varies with load for a spring.
•
The graph shows proportionality up to a point called the ‘proportionality limit’.
•
With increased load, the spring will reach a point at which it will not return to its original shape. This is called the elastic limit. The spring shows ‘plastic’ behaviour beyond here.
29
Extension/Force Graphs extension
Proportionality Limit
Linear Region
0
Load
30 11
Newton’s 1st Law •
If the forces around an object balance (resultant 0N), then it will either:
•
Remain at rest
or
• •
Move at a constant speed in a straight line.
(This is the same as saying constant velocity).
31
Examples of 1st Law
Normal
Normal
Air
Air
Gravity
Gravity
Remains at rest
Moves at a constant speed in a straight line 32
Oil Tube Experiment Fluid Resistance
Falls at a constant speed in a straight line. Gravity
33 12
Unbalanced Forces • If the forces around an object do not balance, then they will cause the object to accelerate (or decelerate).
• The rate of the acceleration depends upon the mass of the object.
• The quantities are linked by the following equation:
F(N ) = m(kg) × a(m s 2 ) 34
Questions •
1. What will be the Force needed to produce an acceleration of 2m/s2 on a mass of 4kg?
•
2. What will be the Force needed to produce an acceleration of 5m/s2 on a mass of 42kg?
•
3. What will be the acceleration produced when a Force of 50N acts upon a mass of 10kg?
35
Newton’s Laws Calculation P
6000 N
Q
400 N 10 000 N
A front wheel drive car is travelling at constant velocity. Q is the force of the air on the moving car. P is the total upward force on both front wheels. (a) Explain why P= 4 000N, Q= 400N (b) Calculate the mass of the car. (c) The 400 N driving force to the left is suddenly doubled.
(i) Calculate the resultant forward driving force.
(ii) Calculate the acceleration of the car.
(iii) Sketch a graph showing how the velocity of the car changes with time (start the graph just before the driving force is doubled.)
13
36
Circular Motion •
When an object is moving in a circle, it must be experiencing a force TOWARDS THE CENTRE of the circle.
•
We call this the CENTRIPETAL Force.
•
This should not be confused with CENTRIFUGAL Force.
•
The centripetal force is directed at right angles to the object’s velocity. object’s path
direction of force
37
Questions •
For each of the following examples, draw a sketch to show the situation, name the force providing the circular motion, and indicate its direction:
•
A) The Earth orbiting the Sun.
•
B) A car rounding a bend.
•
C) A hammer-thrower winding into his throw.
38
Moments •
A moment is a turning force.
•
It is given by:
Moment(Nm) = Force(N ) × distance(m)
39 14
Example •
Calculate the moment produced:
0.1m 100N
40
The Principle of Moments •
If a lever is balanced (in equilibrium) then the total clockwise moments equal the total anti-clockwise moments. It will not move.
•
Because of Newton’s 1st Law, the forces must also balance.
Clockwise moments
Anti-clockwise moments
41
Results Left-Hand Side
Right-Hand Side Weight
Distance
8
4
?
3
4
?
6
5
2
2
?
6
3
?
2
Weight
Distance
2
Wxd
Wxd
42 15
Moments Questions •
1. Explain why a mechanic would choose a long-arm spanner to undo a tight nut.
•
2. In the following diagram, what is the weight of X ?
20 cm
X
25 cm
4N
43
Uses of Levers •
Spanner
•
Nutcracker
•
Scissors
44
Centre of Mass •
Centre of mass is the point on an object that is the ‘average’ position of the mass of the object.
•
The centre of gravity is a point on all objects through which forces appear to act.
•
The two points are the same.
•
The centres of mass of regular objects are obvious. They always lie on a line of symmetry.
•
They are the point under which we place a pivot to balance the object.
45 16
Regular Objects
46
Stability •
Stability tells us how secure something is on the ground.
•
If something is stable, then it will not topple easily.
•
There are two factors to consider when changing the stability of an object:
•
•
The area of the object’s base.
•
The position of the centre of mass of the object.
A stable object will have a BIG base, and a LOW centre of gravity.
47
Simple Addition •
If two vectors are parallel, then they can be simply added or subtracted to give a resultant.
3N
5N
RESULTANT 2N
48 17
2D-Addition •
If the vectors are not parallel we have to draw a scale diagram and add the vectors to give a resultant.
RESULTANT 3m/s
2m/s
2m/s 3m/s
49
Examples • 1. A plane flies North at 40m/s. The wind blows to the East at 15 m/s. Calculate the overall velocity.
• 2i). A falling ball has a weight of 10N and and air resistance of 2N. What the effective downward force on it?
• ii) A wind blows to the left with a force of 2N. Using a vector diagram, calculate the resultant force on the ball.
50
Heat
Sound
Kinetic
Electricity Elastic Potential Energy
Energy Forms Light
Gravitational Potential Energy
Chemical Potential Energy 51 18
Energy Transfers •
When any physical process takes place, there is a transfer of energy from one form to another.
•
This can be shown in an energy flow diagram:
Light Electricity
T.V
Sound Heat
52
Examples of Energy Transfers •
A burning match
•
A lightbulb
•
A petrol lawnmower
•
A car
•
Headphones
•
A microphone
•
A waterfall
53
Kinetic Energy • All objects that are moving have kinetic energy. • It depends on the mass of the object and its speed. • It is measured in joules. KE =
1 2 mv 2
54 19
Gravitational Energy • Gravitational energy is stored in objects that are at a height.
• It depends upon the mass of the object, and how high the object is.
• It measured in joules.
GPE = mgh 55
The Principle of the Conservation of Energy •
Energy cannot be created or destroyed, it simply moves from one form to another.
•
When energy moves from one form to another, the total AMOUNT of energy remains the same.
•
A certain amount of heat energy is always lost to the surroundings in any process.
56
Efficiency •
Efficiency tells us how effective a process or energy transfer is.
•
The more useful energy that is produced, for the least input energy, the more efficient the process is.
•
Efficiency has no unit, and can be expressed as a decimal or percentage.
•
It can be the ratio of power output to input, or energy output to input for a process
Efficiency =
output (×100) input
57 20
Work Done • Work is a type of energy change and is measured in Joules.
• For work to be done, a force must be acting upon an object as it moves through a distance.
• The Work Done is given by: Work Done (J )=Force(N ) × Distance(m)
58
Power • Power is the rate at which energy is transferred. • It is also the rate at which Work is done. • The unit for Power is Watts (W). • Power is calculated from either: Power(W )=
Energy Change(J ) Time Taken(s)
or Power(W )=
Work Done(J ) Time Taken(s)
59
Calculating Personal Power height
time
weight
•
Measure your weight in newtons.
•
Measure the height of the steps in metres.
•
Measure the time taken to climb the steps in seconds.
•
Calculate the Work Done in joules.
•
Calculate the Power of your legs in Watts.
60 21
Pressure •
Pressure tells us how concentrated a force is.
•
It is calculated from:
Pressure( N m 2 )=
Force(N ) Force(N ) 2 or Pressure( N cm )= 2 Area(m ) Area(cm 2 )
Stick to one set of units
61
Examples 2cm
1cm
20g 1cm
1.
Calculate the Volume of the block.
2.
Calculate the block’s density.
3.
Calculate the block’s weight.
4. Calculate the area in contact with the ground.
62
Examples •
Why do camels have large flat feet?
•
Why is it easier to walk in snow shoes in the snow?
63 22
Pressure in Liquids Pressure in a liquid is due to the weight of the liquid above a point. Pressure increases with depth. Pressure will also increase with density of liquid (more weight).
P = ρ gd
We can calculate pressure from:
64
Direction •
The pressure in a liquid acts in ALL directions equally at a point.
•
This is why bubbles are spherical.
65
Questions •
1a). Draw a diagram of the cross section of a dam.
•
b) Explain why it has this shape.
•
2. Calculate the pressure on a scuba diver at a depth of 20m. (The density of water is 1000kg/m3)
•
3. Describe a demonstration to show that Pressure increases with depth in a liquid.
66 23
Non-Renewable Energy Resources •
Non-Renewable resources are resources that are used up and cannot be easily replaced. Examples are fossil fuels and Nuclear fuels.
67
Renewable Energy Resources •
Renewable Energy Resources are energy resources that keep running and do not run-out easily.
68
Nuclear Fusion
•
Safety
•
Pollution
•
Problems
Energy usage
• Transport • Electricity
The Energy Crisis
• Fossil Fuels • Pollution • Depletion
Renewable Alternatives
•
Advantages
•
Unreliable
•
Not Controllable
•
Energy Density
Nuclear Fission
•
Energy Density
• Pollution •
Safety
69 24
General Physics Quantity and symbol Scalar Quantities Vector Quantities
Average Speed, s
Velocity Acceleration, a Mass, m
Weight, W, F
Density, ρ Force, F Load, (Hookes law) Moment Equilibrium Work done, W, E Kinetic energy, KE
Definition/Word equation Scalar quantities only have a magnitude. Vector quantities have a magnitude, a direction and a point of application. Speed is the rate of change of distance. It is a scalar quantity. Speed = Total distance Total time For constant acceleration situations, the average speed is also equal to the average of the initial and final speeds. s = initial speed + final speed 2 Velocity is the rate of change of displacement. It is speed in a given direction. A vector quantity. Acceleration is the rate of change of velocity. Acceleration = Final velocity – initial velocity Time Mass is a property of a body that resists change in motion. Weight is the force on a mass due to the gravitational field of the Planet. It changes from planet to planet. Weights can be compared using a balance. Weight = mass x acceleration due to gravity Weight = mass x gravitational field strength Density is the mass per unit volume. Density = mass volume A force is a push or a pull; it can change the shape, direction, and/or speed of an object. Force = mass x acceleration Load = spring constant x extension Load α extension A moment is the turning affect of a force. Moment = force x perpendicular distance from the pivot When there is no resultant force AND no resulting turning affect, a system is in equilibrium. Work done = Force x distance in the direction of the force = change in energy Kinetic energy is the energy of a body due to its motion. Kinetic energy = ½ x mass x velocity2
25
Symbol equation
Units
s=d t s=u+v 2
m/s cm/s km/h
m/s cm/s km/h a= v–u t
m/s2
W=mxg
Newtons, N
ρ=m V
Kg/m3 g/cm3
F=ma
Newtons, N
F=kl F α l
Newtons, N
Moment = F d
Nm
W = F d = ΔE
Joules, J
KE = ½ m v2
Joules, J
Gravitational energy, GPE Efficiency
Power, P
Gravitational potential energy is the energy of a body due to its position in the gravitational field. Gravitational energy =mass x acceleration due to gravity x height gained/lost Efficiency = useful output x 100% total input Power is the rate at which energy is converted. Power = work done time taken Power = energy change time taken
GPE = m g h
% P=E t
Pressure, p, P
Pressure = force area
P=F A
Fluid Pressure, p, P
Pressure = density of fluid x acceleration due to gravity x height of fluid above
P=ρgh
26
Joules, J
Watts, W N/m2 Pascals, Pa millibar N/m2 Pascals, Pa Millibar
iGCSE Physics Past Paper Questions Paper 1 Compilation General Physics
27
2 11. The diagram shows the level of liquid in a measuring cylinder. cm3 30
liquid 20
What is the volume of the liquid? A
24 cm3
B
28 cm3
C
29 cm3
D
32 cm3
22. A cylindrical can is rolled along the ruler shown in the diagram. final position
starting position can rolled mark on can 0 cm
5
10
15
20
The can rolls over twice. What is the circumference (distance all round) of the can? A
13 cm
B
14 cm
C
26 cm
D
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28
28 cm
25
30 cm
3 33. The graph shows how the speed of a car changes with time.
Q
speed P
O
R
time
Which of the following gives the distance travelled in time interval OR? A
the area OPQR
B
the length PQ
C
the length (QR – PO)
D
the ratio QR/PO
44. A snail crosses a garden path 30 cm wide at a speed of 0.2 cm/s.
movement of snail
30 cm snail
How long does the snail take? A 55.
B
0.0067 s
6.0 s
C
15 s
D
150 s
What are correct units used for mass and for weight? mass
weight
A
kg
kg
B
kg
N
C
N
kg
D
N
N
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[Turn over
4 66. Two objects X and Y are placed on a beam as shown. The beam balances on a pivot at its centre. Y X
pivot What does this show about X and Y? A
They have the same mass and the same density.
B
They have the same mass and the same weight.
C
They have the same volume and the same density.
D
They have the same volume and the same weight.
77. A shop-keeper places two identical blocks of cheese on a set of scales and notices that their combined mass is 240 g. Each block measures 2.0 cm x 5.0 cm x 10.0 cm.
g
What is the density of the cheese? A
0.42 g / cm3
B
0.83 g / cm3
C
1.2 g / cm3
D
2.4 g / cm3
88. The table shows the length of a wire as the load on it is increased. load / N length / cm
0 50.0
10
20
30
52.1
54.1
56.3
Which subtraction should be made to find the extension caused by the 20 N load? A
54.1 cm – 0 cm
B
54.1 cm – 50.0 cm
C
54.1 cm – 52.1 cm
D
56.3 cm – 54.1 cm 0625/1/M/J/02
30
5 99. A child tries to push over a large empty oil drum. Where should the drum be pushed to topple it over with least force? A
B
C
D
10. 10 Which device is designed to convert chemical energy into kinetic energy (energy of motion)? A
an a.c. generator
B
a battery-powered torch
C
a car engine
D
a wind-up mechanical clock
11. 11 A ball is released from rest and rolls down a track from the position shown. What is the furthest position the ball could reach? C ball starts here
B D
A
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[Turn over
6 12 12. Two sharp nails and two blunt nails are held on a piece of wood. Each nail is hit with the same hammer with the same amount of force. When it is hit, which nail causes the greatest pressure on the wood? A
B hammer
sharp nails
C
D hammer
blunt nails
13. The diagram shows a manometer connected to a container of carbon dioxide. 13 container
carbon dioxide 5 cm
mercury manometer Which statement correctly describes the pressure exerted by the carbon dioxide? A
It is equal to the atmospheric pressure.
B
It is equal to 5 cm of mercury.
C
It is equal to 5 cm of mercury above atmospheric pressure.
D
It is equal to 5 cm of mercury below atmospheric pressure.
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2 114. A glass tank contains some water.
V water
T
Q U
S
R The length QR and the width RS of the tank are known. What other distance needs to be measured in order to be able to calculate the volume of the water? A
B
ST
C
SV
D
TU
TV
2 A stopwatch is used to time a race. The diagrams show the watch at the start and at the end of the 15. race.
start 55
end
60
5
55 10
50
40 35
30
45.7 s
B
46.0 s
15
40
25
C
46.5 s
D
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33
47.0 s
20
seconds 35
How long did the race take? A
10
45
20
seconds
5
50
15
45
60
30
25
3 316. The diagram shows a speed-time graph for a body moving with constant acceleration.
speed
0
time
0
What is represented by the shaded area under the graph? A
acceleration
B
distance
C
speed
D
time
417. A tunnel has a length of 50 km. A car takes 20 min to travel between the two ends of the tunnel. What is the average speed of the car? A
2.5 km / h
B
16.6 km / h
C
150 km / h
D
1000 km / h
518. Which statement is correct? A
Mass is a force, measured in kilograms.
B
Mass is a force, measured in newtons.
C
Weight is a force, measured in kilograms.
D
Weight is a force, measured in newtons.
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[Turn over
4 619. Three children, X, Y and Z, are using a see-saw to compare their weights. X
Y
Y
Z
X
Z
Which line in the table shows the correct order of the children’s weights? heaviest
←→
lightest
A
X
Y
Z
B
X
Z
Y
C
Y
X
Z
D
Y
Z
X
720. What apparatus is needed to determine the density of a regularly-shaped block? A
a balance and a ruler
B
a balance and a forcemeter (spring balance)
C
a measuring cylinder and a ruler
D
a measuring cylinder and a beaker
821. A spring is suspended from a stand. Loads are added and the extensions are measured.
spring
stand loads
rule
Which graph shows the result of plotting extension against load?
0
0
load
0
0
0
load
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35
extension
D
extension
C
extension
B
extension
A
0
load
0
0
load
5 922. A student uses a stand and clamp to hold a flask of liquid. Which diagram shows the most stable arrangement? A
B
C
D
10 23. What is the source of the energy converted by a hydro-electric power station? A
hot rocks
B
falling water
C
oil
D
waves
24. A labourer on a building site lifts heavy concrete blocks onto a lorry. Lighter blocks are now lifted 11 the same distance in the same time. What happens to the work done in lifting each block and the power exerted by the labourer? work done in lifting each block
power exerted by labourer
A
decreases
decreases
B
decreases
remains the same
C
increases
increases
D
remains the same
increases
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[Turn over
6
25. The diagram shows an instrument used to measure gas pressure. 12
liquid
What is the instrument called? A
ammeter
B
barometer
C
manometer
D
thermometer
13 26. The diagrams show two divers swimming in the sea and two divers swimming in fresh water. Sea water is more dense than fresh water. On which diver is there the greatest pressure? 0m
0m sea water
A 2m 4m
fresh water
C 2m
B
6m
4m 6m
14 27. When water evaporates, some molecules escape. Which molecules escape? A
the molecules at the bottom of the liquid with less energy than others
B
the molecules at the bottom of the liquid with more energy than others
C
the molecules at the surface with less energy than others
D
the molecules at the surface with more energy than others
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37
D
2 128. The diagram shows a me asuring cylinder. 100 90 80 70 60 50 40 30 20 10
Which unit would be most suitable for its scale? A
mm 2
mm 3
B
cm 2
C
D
cm 3
29. 2 A piece of cotton is me asured betwe en two points on a ruler. cotton
cm
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
When the length of cotton is wound closely around a pen, it goes round six times. six turns of cotton
pen
What is the distance once round the pen? A
2.2 cm
U C L E S 2004
B
2.6 cm
C
13.2 cm
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38
D
15.6 cm
16
3 330. The diagram shows the speed-time graph for an object moving at constant speed. 2 speed m/s 1
0 0
1
2
4
3 time / s
What is the distance travelled by the object in the first 3 s? A
1.5 m
B
2.0 m
C
3.0 m
D
6.0 m
4 A small steel ball is dropped from a low balcony. 31. Ignoring air resistance, which statement describes its motion? A
It falls with constant acceleration.
B
It falls with constant speed.
C
It falls with decreasing acceleration.
D
It falls with decreasing speed.
32. 5 Which statement about the mass of a falling object is correct? A
It decreases as the object falls.
B
It is equal to the weight of the object.
C
It is measured in newtons.
D
It stays the same as the object falls.
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4 633. The weights of four objects, 1 to 4, are compared using a balance.
2
2
1
4 2
3
Which object is the lightest? A
B
object 1
C
object 2
D
object 3
object 4
7 Which of the following is a unit of density? 34. A
cm3 / g
B
g / cm2
C
g / cm3
D
kg / m2
835. A piece of card has its centre of mass at M. Which diagram shows how it hangs when suspended by a thread? A
B
C
D
M M M
M
936. An experiment is carried out to measure the extension of a rubber band for different loads. The results are shown below. load / N length / cm
0
1
15.2
16.2
0
1.0
extension / cm
2
3 18.6
2.1
3.4
Which figure is missing from the table? A
16.5
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17.3
C
17.4
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D
18.3
5
36. The diagram shows a man diving into water. 10
37. Which form of energy is incre asing as he falls? A
chemical
B
gravitational
C
kinetic
D
strain
38. 11 A boy and a girl run up a hill in the same time.
boy weighs 600 N
girl weighs 500 N
The boy weighs more than the girl. Which statement is true about the power produced? A
The boy produces more power.
B
The girl produces more power.
C
They both produce the same power.
D
It is impossible to tell who produces more power.
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6
39. The diagram shows a simple mercury barometer. The barometer re ading is h cm of mercury. 12 S
h
mercury
40. What is the pressure at S? A
approximately z ero
B
atmospheric pressure
C
atmospheric pressure + h cm of mercury
D
h cm of mercury
41. Two boys X and Y e ach have the same total weight and are standing on soft ground. 13 X
Y
Which boy is more likely to sink into the soft ground and why? boy more likely to sink
pressure on soft ground
A
X
larger than Y
B
X
smaller than Y
C
Y
larger than X
D
Y
smaller than X
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2 142. A decorator wishes to calculate the area of a bathroom tile so that he can estimate the amount of adhesive that he needs to buy. What must he use? A
a measuring cylinder only
B
a ruler only
C
a measuring cylinder and a clock only
D
a measuring cylinder and a ruler only
2 The three balls shown are dropped from a bench. 43.
aluminium
lead
wood
Which balls have the same acceleration? A
aluminium and lead only
B
aluminium and wood only
C
lead and wood only
D
aluminium, lead and wood
44. A car accelerates from traffic lights. The graph shows how the car’s speed changes with time. 3 speed m/s 20
0 0
10
time / s
How far does the car travel before it reaches a steady speed? A
10 m
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20 m
C
100 m
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D
200 m
3
45. Which statement is correct? 4
5
A
The mass of a bottle of water at the North Pole is different from its mass at the Equator.
B
The mass of a bottle of water is measured in newtons.
C
The weight of a bottle of water and its mass are the same thing.
D
The weight of a bottle of water is one of the forces acting on it.
Two blocks X and Y are placed on a beam as shown. The beam balances on a pivot at its centre. Y X
pivot
46. What does this show about X and Y? A
They have the same mass and the same density.
B
They have the same mass and the same weight.
C
They have the same volume and the same density.
D
They have the same volume and the same weight.
647. The masses of a measuring cylinder before and after pouring some liquid into it are shown in the diagram. cm3
cm3
200
200
100
100
liquid
mass = 80 g
mass = 180 g
What is the density of the liquid? A
100 g / cm3 120
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B
100 g / cm3 140
C
180 g / cm3 120
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D
180 g / cm3 140
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4 7 A girl and a boy are pulling in opposite directions on a rope. The forces acting on the rope are 48. shown in the diagram. girl
boy 200 N
150 N rope
49. Which single force has the same effect as the two forces shown? A
50 N acting towards the girl
B
350 N acting towards the girl
C
50 N acting towards the boy
D
350 N acting towards the boy
850. Objects with different masses are hung on a 10 cm spring. The diagram shows how much the spring stretches.
10 cm 20 cm 30 cm
100 g
M
The extension of the spring is directly proportional to the mass hung on it. What is the mass of object M? A
110 g
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150 g
C
200 g
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D
300 g
5
51. What is designed to change electrical energy into kinetic energy? 9 A
capacitor
B
generator
C
motor
D
transformer
10 A power station uses nuclear fission to obtain energy. 52. In this process, nuclear energy is first changed into A
chemical energy.
B
electrical energy.
C
gravitational energy.
D
internal energy.
11 53. A ball is released from rest and rolls down a track from the position shown. What is the furthest position the ball could reach?
C
ball starts here
B
D
A
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6
54. A water manometer is used to measure the pressure of a gas supply to a house. It gives a 12 reading of h cm of water. gas supply h cm
55. Why is it better to use water rather than mercury in this manometer? A
h would be too large if mercury were used.
B
h would be too small if mercury were used.
C
The tube would need to be narrower if mercury were used.
D
The tube would need to be wider if mercury were used.
13 56. A farmer has two carts. The carts have the same weight, but one has four narrow wheels and the other has four wide wheels.
narrow wheel
wide wheel
In rainy weather, which cart sinks le s s into soft ground, and why? cart wheels
why
A
narrow
greater pressure on the ground
B
narrow
less pressure on the ground
C
wide
greater pressure on the ground
D
wide
less pressure on the ground
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2
57. A measuring cylinder contains some water. When a stone is put in the water, the level rises. 1 cm3 200
cm3 200
150
150
100
100
50
50
stone
What is the volume of the stone? A
50 cm3
B
70 cm3
75 cm3
C
D
125 cm3
258.The graph represents the movement of a body accelerating from rest. 10 speed m/s
8 6 4 2 0
1
2
3
4
5
time / s
59. After 5 seconds how far has the body moved? A
3
2m
B
10 m
C
25 m
D
50 m
A child is standing on the platform of a station, watching the trains.
A train travelling at 30 m / s takes 3 s to pass the child. What is the length of the train? A
10 m
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30 m
C
90 m
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D
135 m
3
60. Below are four statements about the effects of forces on objects. 4 Three of the statements are correct. Which statement is incorrect? A
A force can change the length of an object.
B
A force can change the mass of an object.
C
A force can change the shape of an object.
D
A force can change the speed of an object.
561. A simple balance has two pans suspended from the ends of arms of equal length. When it is balanced, the pointer is at 0. arm
pivot
pointer 0 pan X
pan Y
Four masses (in total) are placed on the pans, with one or more on pan X and the rest on pan Y. Which combination of masses can be used to balance the pans? A
1 g, 1 g, 5 g, 10 g
B
1 g, 2 g, 2 g, 5 g
C
2 g, 5 g, 5 g, 10 g
D
2 g, 5 g, 10 g, 10 g
6 A person measures the length, width, height and mass of a rectangular metal block. 62. Which of these measurements are needed in order to calculate the density of the metal? A
mass only
B
height and mass only
C
length, width and height only
D
length, width, height and mass
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4 763. Two forces act on an object. In which situation is it impossible for the object to be in equilibrium? A
The two forces act in the same direction.
B
The two forces act through the same point.
C
The two forces are of the same type.
D
The two forces are the same size.
64. 8 The diagram shows four models of buses placed on different ramps. centre of mass
centre of mass
centre of mass
centre of mass
65. How many of these models will fall over? A
9
1
B
2
C
3
D
4
Which form of energy do we receive directly from the Sun? A
chemical
B
light
C
nuclear
D
sound
10 A labourer on a building site lifts a heavy concrete block onto a lorry. He then lifts a light block the 66. same distance in the same time. Which of the following is true? work done in lifting the blocks
power exerted by labourer
A
less for the light block
less for the light block
B
less for the light block
the same for both blocks
C
more for the light block
more for the light block
D
the same for both blocks
more for the light block
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5
67. The diagram shows a thick she et of glass. 11 Which edge must it stand on to cause the gre atest pressure?
A B
D C
68. A manometer is being used to me asure the pressure of the gas inside a tank. A, B, C and D 12 show the manometer at different times. At which time is the gas pressure inside the tank gre atest?
A
B
C
D
gas
13 Brownian motion is se en by looking at smoke particles through a microscope. How do the smoke particles move in Brownian motion? A
all in the same direction
B
at random
C
in circles
D
vibrating about fixed points
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iGCSE Physics Past Paper Questions Paper 3 Compilation General Physics
52
2 11. A group of students attempts to find out how much power each student can generate. The students work in pairs in order to find the time taken for each student to run up a flight of stairs. The stairs used are shown in Fig. 1.1. finishing point
starting point
Fig. 1.1 (a) Make a list of all the readings that would be needed. Where possible, indicate how the accuracy of the readings could be improved. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [4] (b) Using words, not symbols, write down all equations that would be needed to work out the power of a student. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (c) (i)
When the student has reached the finishing point and is standing at the top of the stairs, what form of energy has increased to its maximum? ...................................................................................................................................
(ii)
Suggest why the total power of the student is greater than the power calculated by this method. ................................................................................................................................... ................................................................................................................................... [3]
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3
For Examiner’s Use
22. A small rubber ball falls vertically, hits the ground and rebounds vertically upwards. Fig. 2.1 is the speed-time graph for the ball.
10
B
speed 8 m/s 6
D
4 2 0
A 0
E
C 0.5
1.0
1.5
time / s
2.0
Fig. 2.1 (a) Using information from the graph, describe the following parts of the motion of the ball. (i)
part AB ................................................................................................................................... ................................................................................................................................... ...................................................................................................................................
(ii)
part DE ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... [3]
(b) Explain what is happening to the ball along the part of the graph from B through C to D. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (c) Whilst the ball is in contact with the ground, what is the (i)
overall change in speed, change in speed = ........................................
(ii)
overall change in velocity? change in velocity = ...................................... [2] 0625/3/M/J/02
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4 (d) Use your answer to (c) to explain the difference between speed and velocity. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (e) Use the graph to calculate the distance travelled by the ball between D and E.
distance travelled = ..................................[2] (f)
Use the graph to calculate the deceleration of the ball between D and E.
deceleration = ..................................[2]
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2 13. Fig. 1.1 shows apparatus that may be used to compare the strengths of two springs of the same size, but made from different materials.
spring
scale masses
Fig. 1.1 (a) (i)
Explain how the masses produce a force to stretch the spring. ...................................................................................................................................
(ii) Explain why this force, like all forces, is a vector quantity. ................................................................................................................................... ................................................................................................................................... [2] (b) Fig. 1.2 shows the graphs obtained when the two springs are stretched.
force/N
20 spring 1
15
spring 2
10 5 0
0
10
20
30
extension/mm Fig. 1.2
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40
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3 (i)
State which spring is more difficult to extend. Quote values from the graphs to support your answer.
For Examiner’s Use
................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (ii)
On the graph of spring 2, mark a point P at the limit of proportionality. Explain your choice of point P. ................................................................................................................................... ................................................................................................................................... ...................................................................................................................................
(iii)
Use the graphs to find the difference in the extensions of the two springs when a force of 15 N is applied to each one.
difference in extensions = .................................. [6] 24. The speed of a cyclist reduces uniformly from 2.5 m/s to 1.0 m/s in 12 s. (a) Calculate the deceleration of the cyclist.
deceleration = ..................................[3]
(b) Calculate the distance travelled by the cyclist in this time.
distance = ..................................[2]
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4 35. Fig. 3.1 shows the arm of a crane when it is lifting a heavy box.
1220 N 950 N 40° 30° P box
Fig. 3.1 (a) By the use of a scale diagram (not calculation) of the forces acting at P, find the weight of the box. [5]
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For Examiner’s Use
5 (b) Another box of weight 1500 N is raised vertically by 3.0 m. (i)
Calculate the work done on the box.
work done = .................................. (ii)
The crane takes 2.5 s to raise this box 3.0 m. Calculate the power output of the crane.
power = .................................. [4]
4
Fig. 4.1 shows a sealed glass syringe that contains air and many very tiny suspended dust particles. syringe seal
piston dust particles Fig. 4.1 (a) Explain why the dust particles are suspended in the air and do not settle to the bottom. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3] (b) The air in the syringe is at a pressure of 2.0 × 105 Pa. The piston is slowly moved into the syringe, keeping the temperature constant, until the volume of the air is reduced from 80 cm3 to 25 cm3. Calculate the final pressure of the air.
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2
For Examiner’s Use
16. Fig. 1.1 shows a cycle track. A
B
E
C
v = 6 m/s
D Fig. 1.1 A cyclist starts at A and follows the path ABCDEB. The speed-time graph is shown in Fig. 1.2. B
C
D
E
B
6 speed m/s 5 4 3 2 1 0A 0
10
20
30
40
50
60
70
80
90
100
time / s Fig. 1.2 (a) Use information from Fig. 1.1 and Fig. 1.2 to describe the motion of the cyclist (i)
along AB, ...................................................................................................................................
(ii)
along BCDEB. ................................................................................................................................... ................................................................................................................................... [4]
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3
For Examiner’s Use
(b) The velocity v of the cyclist at C is shown in Fig. 1.1. State one similarity and one difference between the velocity at C and the velocity at E. similarity ........................................................................................................................... difference ......................................................................................................................[2] (c) Calculate (i)
the distance along the cycle track from A to B,
distance = ………………… (ii)
the circumference of the circular part of the track.
circumference = ………………… [4]
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4 27. Fig. 2.1 shows a rock that is falling from the top of a cliff into the river below.
cliff
falling rock
river
Fig. 2.1 (a) The mass of the rock is 75 kg. The acceleration of free fall is 10 m/s2. Calculate the weight of the rock.
weight = …………………[1] (b) The rock falls from rest through a distance of 15 m before it hits the water. Calculate its kinetic energy just before hitting the water. Show your working.
kinetic energy = …………………[3] (c) The rock hits the water. Suggest what happens to the kinetic energy of the rock during the impact. .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3]
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5
For Examiner’s Use
38. A large spring is repeatedly stretched by an athlete to increase the strength of his arms. Fig. 3.1 is a table showing the force required to stretch the spring. extension of spring / m force exerted to produce extension / N
0.096
0.192
0.288
0.384
250
500
750
1000
Fig. 3.1 (a) (i)
State Hooke’s law. ................................................................................................................................... ...............................................................................................................................[1]
(ii)
Use the results in Fig. 3.1 to show that the spring obeys Hooke’s law.
[1] (b) Another athlete using a different spring exerts an average force of 400 N to enable her to extend the spring by 0.210 m. (i)
Calculate the work done by this athlete in extending the spring once.
work done = ………………… (ii)
She is able to extend the spring by this amount and to release it 24 times in 60 s. Calculate the power used by this athlete while doing this exercise.
power = ………………… [4]
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2 19. A solid plastic sphere falls towards the Earth. Fig. 1.1 is the speed-time graph of the fall up to the point where the sphere hits the Earth’s surface. 140 speed m/s
R
120
S
T
100 80 60 Q
40 20 0
P 0
10
20
30
40
50
60
70 80 time / s
90
100 110
Fig. 1.1 (a) Describe in detail the motion of the sphere shown by the graph. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [3]
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3 (b) On Fig. 1.2, draw arrows to show the directions of the forces acting on the sphere when it is at the position shown by point S on the graph. Label your arrows with the names of the forces. [2]
Fig. 1.2 (c) Explain why the sphere is moving with constant speed at S. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (d) Use the graph to calculate the approximate distance that the sphere falls (i)
between R and T,
(ii)
between P and Q.
distance = ………………. [2]
distance = ………………. [2]
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For Examiner’s Use
4 210. Fig. 2.1 shows a simple pendulum that swings backwards and forwards between P and Q.
support string
P
R
Q
pendulum bob
Fig. 2.1 (a) The time taken for the pendulum to swing from P to Q is approximately 0.5 s. Describe how you would determine this time as accurately as possible. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (b) (i)
State the two vertical forces acting on the pendulum bob when it is at position R. 1. ............................................................................................................................... 2. .......................................................................................................................... [1]
(ii)
The pendulum bob moves along the arc of a circle. State the direction of the resultant of the two forces in (i). .............................................................................................................................. [1]
(c) The mass of the bob is 0.2 kg. During the swing it moves so that P is 0.05 m higher than R. Calculate the increase in potential energy of the pendulum bob between R and P.
potential energy = ………………. [2]
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5 311. A mass of 3.0 kg accelerates at 2.0 m/s2 in a straight line. (a) State why the velocity and the acceleration are both described as vector quantities. .......................................................................................................................................... ..................................................................................................................................... [1] (b) Calculate the force required to accelerate the mass.
force = ………………. [2] (c) The mass hits a wall. The average force exerted on the wall during the impact is 120 N. The area of the mass in contact with the wall at impact is 0.050 m2. Calculate the average pressure that the mass exerts on the wall during the impact.
pressure = ………………. [2]
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2 112. A bus travels from one bus stop to the next. The journey has three distinct parts. Stated in order they are uniform acceleration from rest for 8.0 s, uniform speed for 12 s, non-uniform deceleration for 5.0 s. Fig. 1.1 shows only the deceleration of the bus. 15 speed m/s 10
5
0
0
5
10
15
time/s
20
25
Fig. 1.1 (a) On Fig. 1.1, complete the graph to show the first two parts of the journey.
[3]
(b) Calculate the acceleration of the bus 4.0 s after leaving the first bus stop.
acceleration = ........................[2] (c) Use the graph to estimate the distance the bus travels between 20 s and 25 s.
estimated distance = ........................[2] (d) On leaving the second bus stop, the uniform acceleration of the bus is 1.2 m / s2. The mass of the bus and passengers is 4000 kg. Calculate the accelerating force that acts on the bus.
force = ........................[2] (e) The acceleration of the bus from the second bus stop is less than that from the first bus stop. Suggest two reasons for this. 1. ...................................................................................................................................... .......................................................................................................................................... 2. ...................................................................................................................................... ......................................................................................................................................[2] © UCLES 2006
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3 213. A student sets up the apparatus shown in Fig. 2.1 in order to find the resultant of the two tensions T1 and T2 acting at P. When the tensions T1, T2 and T3 are balanced, the angles between T1 and the vertical and T2 and the vertical are as marked on Fig. 2.1. pulley
pulley
T1 = 6.0 N 69°
T2 = 8.0 N
44°
vertical board
P T3
Fig. 2.1 In the space below, draw a scale diagram of the forces T1 and T2. Use the diagram to find the resultant of the two forces.
State (a) the scale used,
scale = ........................................
(b) the value of the resultant,
value = ........................................
(c) the direction of the resultant.
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direction = ........................................ [6]
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4 314. An electric pump is used to raise water from a well, as shown in Fig. 3.1. pump ground
well
Fig. 3.1 (a) The pump does work in raising the water. State an equation that could be used to calculate the work done in raising the water. ......................................................................................................................................[2] (b) The water is raised through a vertical distance of 8.0 m. The weight of water raised in 5.0 s is 100 N. (i)
Calculate the work done in raising the water in this time.
work done = .......................[1] (ii)
Calculate the power the pump uses to raise the water.
power = ........................[1] (iii)
The energy transferred by the pump to the water is greater than your answer to (i). Suggest what the additional energy is used for. ..............................................................................................................................[1]
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Topic 2: Thermal Physics
1
Solids • The particles in solids are tightly held together by strong forces. • They vibrate around mean positions. • The higher the temperature, the more vibrational kinetic energy the particles have. • Solids have a rigid shape.
2
Liquids • In liquids the forces are strong, but the vibrating particles are not fixed in position. • The particles can move but they are held close to their neighbours. • Liquids do not keep their shape.
3 71
Gases • In gases the forces are very weak and they are virtually free to move around their container. • The particles occasionally collide. • Gases expand to fill their container. • The collisions between the particles and the container walls provides pressure.
4
Changing State • When a material changes from one state to another, bonds are either broken or created. • When bonds are broken, heat must be supplied. When bonds are created, heat is released. • When materials change state there is no change in the temperature.
5
Phase Changes • The phase change from solid to liquid is called ‘fusion’. • The phase change from liquid to gas is called ‘vaporisation’. • The energy required to effect the phase change is called the ‘Latent Heat’. • The Latent Heat required per kg is called the ‘Specific Latent Heat’.
6 72
Phases Changes (Graphical) vaporisation
Temperature liquid water
fusion
Time
7
Latent Heat Calculations • The Specific Latent Heat of a material is given the symbol l. • From the definition, we have the following relationship:
H = ml H-J m - kg l - J/kg
8
Heat Capacity • Whilst a material is being heated within a certain state of matter, its temperature will rise. • The temperature rise depends upon the mass of the material, the type of material and the amount of heat supplied. • The property of a material that represents how much heat is needed to raise its temperature is called its ‘Specific Heat Capacity’ and is given the symbol c.
9 73
Calculations • To calculate heat required we use:
H = mcΔT H-J m - kg C - J/kg/ ºC ∆T - ºC
10
Constant Volume • If we increase the temperature of a gas in a
container at a constant volume, the particles will move with more energy, and so there will be more collisions, and so greater pressure:
Pressure increases with Temperature
11
Constant Pressure •
If we increase the temperature of a gas in a container at a constant pressure, the particles will move with more energy, but they need more space to keep the collisions constant and so there will be a greater volume:
Volume increases with Temperature
12 74
Constant Temperature •
If we keep the temperature of a gas constant, we keep the kinetic energy of the particles constant.
•
Decreasing the volume of the gas’ container will increase the number of collisions of the particles with the container.
•
The pressure of the gas will increase.
•
Pressure and Volume changes are described by the following relationship:
P1V1 = P2V2 13
Brownian Motion •
When pollen grains are placed on the surface of a liquid and a strong light source is used to illuminate the pollen, the pollen is seen to move randomly.
•
This movement is called ‘Brownian Motion’ and cause by the invisible water particles hitting the pollen grains.
14
Expansion
•
When particles are heated they gain energy.
•
They become more spaced-out, and the material gets bigger.
•
We say that the material expands.
•
Generally, objects expand as they get hotter and contract as they get cooler.
•
Liquids expand more than solids on heating, and gases expand more than liquids.
•
Solids expand with the greatest force. Gases expand with the least force.
15 75
Questions on Expansion •
Why do walls have expansion joints?
•
Why are pylon electrical cables tighter in winter?
•
Why do railway lines leave regular gaps between them?
16
Temperature Scales •
The most common temperature scale that is used is the Celsius scale. This has its zero at the freezing point of water, and the boiling point of water is 100°C.
•
In Physics, the Kelvin scale (or Absolute Temperature scale) is often used.
•
This is often more sensible as the zero is defined as the point at which the particles have no kinetic energy (Absolute Zero).
•
To convert between Celsius and Kelvin, we add 273°C.
•
A rise of 1K is the same as a rise of 1°C.
17
Internal Energy • The Kelvin Temperature is proportional to the average kinetic energy of the particles.
18 76
Evaporation • Evaporation is a process by which a liquid cools due to the fact that particles are lost from its surface.
• The higher energy particles will be more
likely to leave the liquid, so lowering the average KE of the particles remaining in the liquid. The temperature will thus be lowered.
• Increasing the exposed surface area of the liquid, or increasing the movement of air will increase the rate of evaporation.
19
Changing State When a material changes from one state to another, bonds are either broken or created. This involves an associated Internal Energy change. When bonds are broken, heat must be supplied. When bonds are created, Heat is released. Since the energy changes are entirely Internal, there is no change in kinetic energy of the particles, and hence no change in the temperature of the material.
20
Thermometry To make a thermometer, we need a property that changes with temperature in a linear fashion. We then need to calibrate the thermometer by choosing two fixed points. The fixed points for calibration are the boiling point of water (100°C) and the freezing point of water (0°C). The scale is then divided into 100 equal parts for interpolation.
21 77
Liquid in Glass Thermometers •
Liquid in glass thermometers have liquid in a glass bulb. As the liquid is heated it expands and its level rises up the scale.
•
The choice of liquid, the thinness of the bore or the size of the bulb will affect the sensitivity of the thermometer.
•
The choice of liquid will affect the range of the thermometer.
22
Thermocouple •
A thermocouple is a junction of two different metals.
•
Electrons will move across the junction creating a measurable voltage.
•
The higher the temperature, the more energy the electrons will have, more electrons will move and we get a greater voltage.
•
The voltage is then calibrated.
•
High temperatures can be quickly recorded.
23
Heat Transfer •
Heat flows from hot areas to cold areas.
•
In solids, heat moves by conduction.
•
In liquids and gases (fluids), heat moves by convection.
•
In a vacuum heat has to move by radiation.
24 78
Conduction
Heat
Heat
•
Heat moves from particle to particle as they collide.
•
Poor conductors are called insulators.
•
Solids are the best conductors (especially metals).
•
Gases are the best insulators.
25
Questions on Conduction. 1. Why does a robin fluff up its feathers in Winter? 2. Why is a string vest warmer than a cotton vest? 3. Design an experiment to compare conductors.
26
Convection Cool fluid in a beaker.
Convection currents circulate the heat.
Heat source is applied.
Warm fluid expands and rises. (low density)
Denser Cool fluid sinks Heat
27 79
Questions on Convection •
Why should you stay close to the ground in a smokefilled room?
•
Why is the heating element at the bottom of a kettle?
28
Radiation Hot object (warmer than surroundings).
Infra-red light energy emitted..
Cooler object
29
Radiation •
Black objects are better radiators and absorbers than white or shiny objects.
•
Rough objects are better radiators and absorbers than shiny or smooth objects.
30 80
Questions on Radiation •
Why are houses often painted white in hot countries?
•
Why do marathon runners wear an aluminium blanket at the end of a race?
31
The Vacuum Flask stopper
silver surface
vacuum
32
81
1
Thermal Physics Quantity and symbol
Symbol equation
Definition
The temperature of a gas is related to the motion of its particles. The faster, and Temperature, T, θ therefore the more energetic the particles the hotter the gas. The random, jerky motion of particles (pollen in water, smoke in air) in a Brownian Motion suspension is evidence for the kinetic model of matter. The massive particles are moved by light, fast moving molecules. The more energetic molecules escape from the surface of a liquid. This leaves the Evaporation liquid left behind with a lower average KE, and hence a cooler liquid. For a fixed mass of gas, the pressure is Pα1 inversely proportional to the volume, (at V Boyles’ Law constant temperature) PV = k For a fixed mass of gas, the volume is VαT Charles’ Law directly proportional to the temperature, (at V=kT constant pressure) For a fixed mass of gas, the pressure is PαT directly proportional to the temperature, (at P=kT Pressure Law constant volume) For a fixed mass of gas, the PV = k Pressure x Volume = a constant T Gas Law Temperature P1V1 = P2V2 T1 T2 The amount of heat energy required to c=E Thermal Capacity, c change the temperature of a body by 1 oC ΔT The amount of heat energy required to c=Q Specific Heat change the temperature of a unit mass of a mΔT Capacity, c o substance by 1 C The amount of energy required to change Latent Heat, L the state of a body without a change in temperature The amount of energy required to change L=Q Specific Latent Heat the state of unit mass of substance, from m of Fusion, L solid to liquid without a change in temperature The amount of energy required to change L=Q Specific Latent Heat the state of unit mass of a substance from m of Vaporisation, L liquid to gas without a change in temperature The movement of heat energy by the passing on of vibrations from particle to Conduction particle.
82
units o
C, K
Temperature must be the absolute temperature in Kelvin, K. The other quantities must be consistent. J/ oC J/kg oC Jkg oC J J/kg J/g J/kg J/g
2
Convection Radiation
The movement of heat energy by the mass movement of fluids, due to expansion and density changes due to heating. The movement of heat energy by the form of an electromagnetic wave. (Infrared)
83
iGCSE Physics Past Paper Questions Paper 1 Compilation Thermal Physics
84
7 141. The diagram represents molecules in a liquid. A and C are molecules with a high amount of energy. B and D are molecules with a low amount of energy. Which molecule is most likely to be leaving the liquid by evaporation?
A
B
D
C
152. The size of a balloon increases when the pressure inside it increases. The balloon gets bigger when it is left in the heat from the Sun. cool balloon
hot balloon
Why does this happen? A
The air molecules inside the balloon all move outwards when it is heated.
B
The air molecules inside the balloon are bigger when it is heated.
C
The air molecules inside the balloon move more quickly when it is heated.
D
The number of air molecules inside the balloon increases when it is heated.
3. What must expand in order to show the temperature rise in a mercury-in-glass thermometer? 16 A
the glass bulb
B
the glass stem
C
the mercury
D
the vacuum
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8 174. The table shows the melting points and boiling points of four substances. Which substance is a liquid at a room temperature of 20 oC? substance
melting point / oC
boiling point / oC
A
–101
–35
B
–39
357
C
30
2100
D
327
1750
18 5. A bar made of half wood and half copper has a piece of paper wrapped tightly round it. The bar is heated strongly at the centre for a short time, and the paper goes brown on one side only. wood paper copper
heat Which side goes brown, and what does this show about wood and copper? brown side
wood
copper
A
copper
conductor
insulator
B
copper
insulator
conductor
C
wood
conductor
insulator
D
wood
insulator
conductor
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9
6. The diagrams show part of a water-heating system which is working by convection. 19 Which diagram shows the most likely flow of water in the system? A
B
hot water tank
hot water tank boiler
boiler
heat
heat
C
D
hot water tank
hot water tank boiler
boiler
heat
9
heat
7.19 The diagram shows a heater used to heat a tank of cold water. 20 A drop of water from a tap falls onto the surface of some water of constant depth.
water lagging view from above tank heater Water waves spread out on the surface of the water. Which statement is true? A
What is theare main process by moves The waves longitudinal andwhich travelheat at the samethrough speed the in allwater? directions.
B
The are longitudinal and travel more quickly in one direction than in others. A waves conduction
C
The are transverse and travel at the same speed in all directions. B waves convection
D
The are transverse and travel more quickly in one direction than in others. C waves evaporation D
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20 What causes refraction when light travels from air into glass? A
87
The amplitude of the light waves changes.
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7 158. Two metal boxes containing air are standing in a room. Box X is on top of a heater. Box Y is on a bench. The boxes are left for a long time. Y
X
heater
bench
Which line in the table best describes the average speed of the molecules in the containers? box X
box Y
A
fast
zero
B
fast
slow
C
slow
fast
D
zero
fast
9. The top of the mercury thread in a mercury-in-glass thermometer reaches point X at 0 °C and 16 point Z at 100 °C. Z Y
X W
Where might it be at a temperature below the ice-point? A
point W
B
point X
C
point Y
D
point Z
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8 17 10. The same quantity of heat energy is applied to four different blocks. The temperature rise produced is shown on each block. Which block has the highest thermal capacity? A
B
temperature rise is 3 °C
temperature rise is 6 °C
C
D
temperature rise is 18 °C
temperature rise is 9 °C
11. A person holds a glass beaker in one hand and fills it quickly with hot water. It takes several 18 seconds before his hand starts to feel the heat. Why is there this delay? A
Glass is a poor conductor of heat.
B
Glass is a good conductor of heat.
C
Water is a poor conductor of heat.
D
Water is a good conductor of heat.
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7 14 A student places his thumb firmly on the outlet of a bicycle pump, to stop the air coming out.
trapped air direction of motion handle What happens to the pressure and to the volume of the trapped air as the pump handle is pushed in? pressure
volume
A
decreases
decreases
B
decreases
remains the same
C
increases
decreases
D
increases
remains the same
15 A balloon is inflated in a cold room. When the room becomes much warmer, the balloon becomes larger. How does the behaviour of the air molecules in the balloon explain this? A
The molecules become larger.
B
The molecules evaporate.
C
The molecules move more quickly.
D
The molecules repel each other. 9
19 The diagram shows a block of ice placed in a warm room. At which point is the temperature the lowest? $
D! &$"'(
)&%
!"#
%$C "
B
# A
20 The drawing shows a wave. Which labelled distance is the wavelength? UCLES 2004
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8
12. A substance is heated at a steady rate. It changes from a solid to a liquid, and then to a gas. 16 The graph shows how its temperature changes with time.
S temperature 5 R
Q 11 The diagram shows a thick sheet of glass. Which edge must it stand on P to cause the greatest pressure?
A
time
B Which parts of the graph show a change of state taking place? A
P and R
B
P and S
C
Q and R
D
Q and S
D C
13. 17 An engineer wants to fix a steel washer on to a steel rod. The rod is just too big to fit into the hole 12 A of manometer the washer. is being used to measure the pressure of the gas inside a tank. A, B, C and D show the manometer at different times. steel steel rod At which time is washer the gas pressure inside the tank greatest?
A
B
C
How can the engineer fit the washer onto the rod? gas A cool the washer and put it over the rod B
cool the washer and rod to the same temperature and push them together
C
heat the rod and then place it in the hole
D
heat the washer and place it over the rod
13 14. Brownian motion is seen by looking at smoke particles through a microscope. How do the smoke particles move in Brownian motion? A
all in the same direction
B
at random
C
in circles
D
vibrating about fixed points
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D
9
15. An experiment is set up to find out which metal is the best conductor of heat. Balls are stuck with 18 wax to rods made from different metals, as shown in diagram X. The rods are heated at one end. Some of the balls fall off, leaving some as shown in diagram Y. Which labelled metal is the best conductor of heat? diagram X
diagram Y A
h
e
a
t
B
h
before heating
C
e
a
D
t
after heating
16. 19 Thermometer X is held above an ice cube and thermometer Y is held the same distance below the ice cube. After several minutes, the reading on one thermometer changes. The ice cube does not melt. thermometer X
ice cube
thermometer Y
Which thermometer reading changes and why? thermometer
reason
A
X
cool air rises from the ice cube
B
X
warm air rises from the ice cube
C
Y
cool air falls from the ice cube
D
Y
warm air falls from the ice cube
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7
17. Viewed through a microscope, very small particles can be seen moving with Brownian motion. 14 Which line in the table is correct? type of motion of particles
particles are suspended in
A
vibration
a liquid or a gas
B
vibration
a solid, a liquid or a gas
C
random
a liquid or a gas
D
random
a solid, a liquid or a gas
15 A measured mass of gas is placed in a cylinder at atmospheric pressure and is then slowly 18. compressed. piston gas piston pushed in
The temperature of the gas does not change. What happens to the pressure of the gas? A
It drops to zero.
B
It decreases, but not to zero.
C
It stays the same.
D
It increases.
16 19. The graph shows the change in temperature of a material as it is heated. Which part on the graph shows when the material is boiling?
D temperature C B A time
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8
20. An experiment is set up as shown. 17
pressure gauge
air flask water
heat What does the pressure gauge show as the air in the flask becomes hotter? A
a steady pressure
B
a decrease in pressure
C
an increase in pressure
D
an increase and then a decrease in pressure
18 An iron bar is held with one end in a fire. The other end soon becomes too hot to hold.
hand
fire iron bar
21. How has the heat travelled along the iron bar? A
by conduction
B
by convection
C
by expansion
D
by radiation
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6
22. Driving a car raises the temperature of the tyres. 14 This causes the pressure of the air in the tyres to increase. Why is this? A
Air molecules break up to form separate atoms.
B
Air molecules expand with the rise in temperature.
C
The force between the air molecules increases.
D
The speed of the air molecules increases.
23. 15 To mark a temperature scale on a thermometer, fixed points are needed. Which is a fixed point? A
the bottom end of the thermometer tube
B
the top end of the thermometer tube
C
the temperature of pure melting ice
D
the temperature of pure warm water
24. Four blocks, made of different materials, are each given the same quantity of internal (heat) 16 energy. Which block has the greatest thermal capacity?
© UCLES 2006
A
B
C
D
temperature rise = 2 oC
temperature rise = 4 oC
temperature rise = 6 oC
temperature rise = 8 oC
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7
25. A long thin bar of copper is heated evenly along its length. 17 copper bar
heat What happens to the bar? A
It becomes lighter.
B
It becomes longer.
C
It becomes shorter.
D
It bends at the ends.
18 A beaker contains water at room temperature. water
X
Y
26. How could a convection current be set up in the water? A
cool the water at X
B
cool the water at Y
C
stir the water at X
D
stir the water at Y
8 19 Two plastic cups are placed one inside the other. Hot water is poured into the inner cup and a lid is put on top as shown. lid small spacer small air gap hot water bench
27. Which statement is correct? A
Heat loss by radiation is prevented by the small air gap.
B
No heat passes through the sides of either cup.
C
The bench is heated by convection from the bottom of the outer cup.
D
The lid is used to reduce heat loss by convection.
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iGCSE Physics Past Paper Questions Paper 3 Compilation Thermal Physics
97
5 31.
Fig. 3.1 is an attempt to show the molecules in water and the water vapour molecules over the water surface.
For Examiner’s Use
water vapour molecules
water molecules Fig. 3.1 (a) Explain, in terms of the energies of the molecules, why only a few water molecules have escaped from the water surface. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (b) State two ways of increasing the number of water molecules escaping from the surface. 1 ....................................................................................................................................... 2 .................................................................................................................................. [2] (c) Energy is required to evaporate water. Explain, in molecular terms, why this energy is needed. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2]
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6 42. (a) Fig. 4.1 shows a cylinder containing air at a pressure of 1.0 × 105 Pa. The length of the air column in the cylinder is 80 mm. 80 mm
air piston
cylinder Fig. 4.1
The piston is pushed in until the pressure in the cylinder rises to 3.8 × 105 Pa. Calculate the new length of the air column in the cylinder, assuming that the temperature of the air has not changed.
new length = .................................. [3] (b) Fig. 4.2 shows the same cylinder containing air.
air Fig. 4.2 The volume of the air in the cylinder changes as the temperature of the air changes. (i)
The apparatus is to be used as a thermometer. Describe how two fixed points, 0 °C and 100 °C, and a temperature scale could be marked on the apparatus. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ...................................................................................................................................
(ii)
Describe how this apparatus could be used to indicate the temperature of a large beaker of water. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... [5] 0625/3/M/J/02
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For Examiner’s Use
[4] 4
Fig. 4.1 shows a sealed glass syringe that contains air and many very tiny suspended dust 5 particles. 3. (b) Another box of weight 1500 N is raised vertically by 3.0 m. (i)
syringe Calculate the work done on the box. seal
piston work done = ..................................
dust particles (ii)
For Examiner’s Use
The crane takes 2.5 s to raise this box 3.0 m. Calculate the power output of the Fig. 4.1 crane.
(a) Explain why the dust particles are suspended in the air and do not settle to the bottom. .......................................................................................................................................... .......................................................................................................................................... power = .................................. [4] .......................................................................................................................................... 4
Fig.......................................................................................................................................[3] 4.1 shows a sealed glass syringe that contains air and many very tiny suspended dust particles. (b) The air in the syringe is at a pressure of 2.0 × 105 Pa. The piston is slowly moved into the syringe, keeping the temperature constant, until the volume of the air is reduced from syringe 80 cm3 to 25 cm3. Calculate the final pressure of the air. seal
piston pressure = ..................................[3]
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Fig. 4.1
[Turn over
(a) Explain why the dust particles are suspended in the air and do not settle to the bottom. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3] (b) The air in the syringe is at a pressure of 2.0 × 105 Pa. The piston is slowly moved into the syringe, keeping the temperature constant, until the volume of the air is reduced from 80 cm3 to 25 cm3. Calculate the final pressure of the air.
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100
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6 54. Fig. 5.1 shows a thermocouple set up to measure the temperature at a point on a solar panel. Sun's rays surface of solar panel
Z X
cold junction Y
hot junction
Fig. 5.1 (a) X is a copper wire. (i)
Suggest a material for Y. ...................................................................................................................................
(ii)
Name the component Z. ................................................................................................................................... [2]
(b) Explain how a thermocouple is used to measure temperature. .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3] (c) Experiment shows that the temperature of the surface depends upon the type of surface used. Describe the nature of the surface that will cause the temperature to rise most. .......................................................................................................................................... ......................................................................................................................................[1]
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For Examiner’s Use
6 45. (a) Two identical open boxes originally contain the same volume of water. One is kept at 15 °C and the other at 85 °C for the same length of time. Fig. 4.1 shows the final water levels.
15 °C
85 °C Fig. 4.1
With reference to the energies of the water molecules, explain why the levels are different. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3] (b) In an experiment to find the specific latent heat of vaporisation of water, it took 34 500 J of energy to evaporate 15 g of water that was originally at 100 °C. A second experiment showed that 600 J of energy was lost to the atmosphere from the apparatus during the time it took to evaporate 15 g of water. Calculate the specific latent heat of vaporisation of water that would be obtained from this experiment.
specific latent heat = …………………[3]
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7 56. (a) Fig. 5.1 shows two identical metal plates. The front surface of one is dull black and the front surface of the other is shiny silver. The plates are fitted with heaters that keep the surfaces of the plates at the same temperature. dull black
For Examiner’s Use
shiny silver
Fig. 5.1 (i)
State the additional apparatus needed to test which surface is the best emitter of heat radiation. ...................................................................................................................................
(ii)
State one precaution that is needed to ensure a fair comparison. ................................................................................................................................... ...................................................................................................................................
(iii)
State the result that you expect. ...................................................................................................................................
(iv)
Write down another name for heat radiation. ................................................................................................................................... [4]
(b) In the space below, draw a labelled diagram of an everyday situation in which a convection current occurs. Mark the path of the current with a line and show its direction with arrows.
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[3]
[Turn over
6 47.
Fig. 4.1 shows apparatus that a student uses to make an estimate of the specific heat capacity of iron.
electrical heater
thermometer
iron block
Fig. 4.1 (a) The power of the heater is known. State the four readings the student must take to find the specific heat capacity of iron. 1. ...................................................................................................................................... 2. ...................................................................................................................................... 3. ...................................................................................................................................... 4. ................................................................................................................................. [3] (b) Write down an equation, in words or in symbols, that could be used to work out the specific heat capacity of iron from the readings in (a).
[2]
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For Examiner’s Use
7 (c) (i)
Explain why the value obtained with this apparatus is higher than the actual value. ................................................................................................................................... .............................................................................................................................. [1]
(ii)
State one addition to the apparatus that would help to improve the accuracy of the value obtained. ................................................................................................................................... .............................................................................................................................. [1]
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For Examiner’s Use
8 5 8. (a) Fig. 5.1 shows the paths of a few air molecules and a single dust particle. The actual air molecules are too small to show on the diagram. paths of air molecules dust particle
Fig. 5.1 Explain why the dust particle undergoes small random movements. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [4] (b) Fig. 5.2 shows the paths of a few molecules leaving the surface of a liquid. The liquid is below its boiling point.
air and vapour liquid Fig. 5.2 (i)
State which liquid molecules are most likely to leave the surface. ................................................................................................................................... .............................................................................................................................. [1]
(ii) Explain your answer to (i). ................................................................................................................................... ................................................................................................................................... .............................................................................................................................. [2]
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5 4 9. (a) State two differences between evaporation of water and boiling of water. 1. ...................................................................................................................................... 2. ..................................................................................................................................[2] (b) The specific latent heat of vaporisation of water is 2260 kJ / kg. Explain why this energy is needed to boil water and why the temperature of the water does not change during the boiling. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3] (c) A laboratory determination of the specific latent heat of vaporisation of water uses a 120 W heater to keep water boiling at its boiling point. Water is turned into steam at the rate of 0.050 g / s. Calculate the value of the specific latent heat of vaporisation obtained from this experiment. Show your working.
specific latent heat of vaporisation = ........................[3]
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For Examiner’s Use
6 510. (a) Fig. 5.1 shows a tank used for evaporating salt solution to produce crystals. evaporating tank steam in salt solution steam out Fig. 5.1 Suggest two ways of increasing the rate of evaporation of the water from the solution. Changes may be made to the apparatus, but the rate of steam supply must stay constant. You may assume the temperature of the salt solution remains constant. 1. ...................................................................................................................................... .......................................................................................................................................... 2. ...................................................................................................................................... ......................................................................................................................................[2] (b) A manufacturer of liquid-in-glass thermometers changes the design in order to meet new requirements. Describe the changes that could be made to (i)
give the thermometer a greater range, ..............................................................................................................................[1]
(ii)
make the thermometer more sensitive. ..............................................................................................................................[1]
(c) A toilet flush is operated by the compression of air. The air inside the flush has a pressure of 1.0 × 105 Pa and a volume of 150 cm3. When the flush is operated the volume is reduced to 50 cm3. The temperature of the air remains constant during this process. Calculate the new pressure of the air inside the flush.
pressure = .......................[2]
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Topic 3: Waves
1
Transverse Waves Wavelength amplitude amplitude Wavelength Frequency=Number of Waves per second (Hz)
2
Types of Waves •
Waves carry energy without matter being transferred.
•
There are two types of wave motion:
•
Transverse.
•
Longitudinal.
3 109
Transverse Waves
•
In a transverse wave, the wave motion is at right angles to the direction of the wave.
•
The Energy flows in a direction at right angles to the wave motion.
•
Examples of transverse waves are Light, Pond-ripples, Seismic Swaves.
4
Longitudinal Waves
In a longitudinal wave, the wave motion is along the direction of the wave. It consists of a series of compressions and rarefractions.
The Energy flows in the same direction as the wave motion.
Examples of longitudinal waves are Sound and Seismic P-waves.
5
Reflection •
If waves hit a boundary, they will reflect.
•
The angle of incidence will be equal to the angle of reflection.
Incident wavefronts
Reflected wavefronts
Reflecting Surface Normal
6 110
Refraction •
If a wave changes speed, its direction will change.
•
If it slows-down it will bend towards the normal.
•
If the wave speeds-up it will bend away from the normal. Incident wavefronts
Boundary Refracted Wavefronts Normal
7
Diffraction •
If a wave encounters a gap that is of a similar size as the wavelength of the wave, we will get diffraction.
•
The wave appears to spread-out from the gap.
8
Period of a Wave • The period of a wave is the time taken for the wave to complete one cycle.
• There is a simple relationship between Period (T) and Frequency (f):
Period =
1 frequency
9 111
The Wave Equation • The wave-speed (v), the frequency (f) and the wavelength (λ) are linked with the wave equation:
v(m s) = f (Hz)λ (m)
10
Wave Equation Questions 1. The speed of sound in air is 340m/s. A musical note has a wavelength of 0.6m. Calculate the frequency of the note. 2. In a concert hall, an echo is heard 0.5s after the note was played. How long is the hall? 3 The speed of light in air is 300 000 000 m/s. The frequency of the “Radio Uno” radio station is 567 kHz. Calculate the wavelength of the radio waves. 4 What would be the Period of one these waves?
11
Reflection in a Plane Mirror •
In a plane mirror, angle of incidence=angle of reflection.
•
The mirror produces a virtual upright image behind the mirror, the same size as the object and at the same distance as the object.
•
The image is laterality inverted.
Eye
Object
Image
112
12
Refraction in a Rectangular Block Air
Glass
Air
r i r i
13
Refractive Index • When light moves through a medium, it is slowed down.
• A high refractive index (n) means that the
light’s speed (vm) is slow in the medium. We define refractive index in terms of the speed of light (c)
n=
c vm 14
Refraction •
When light moves from air to a medium it bends towards the normal. The angles depend upon the refractive index of the material concerned. air
medium r
i
n=
sin i sin r
15 113
Spectrum of Visible Light • The colours of visible light can be arranged according to their wavelength.
• We normally say that there are seven distinct
colours, although the spectrum is continuous.
• In order of increasing wavelength, the colours are:
• Red, Orange, Yellow, Green, Blue, Indigo & Violet.
• Each colour of light refracts by a different
amount; violet light the most, red light the least.
16
Dispersion
White light
screen prism
17
Refraction in a Semi-Circular Block r i
Refraction
C
Critical Angle
i
r
Total Internal Reflection
18 114
Total Internal Reflection •
If the angle of Incidence is greater than the Critical angle then the light undergoes TOTAL INTERNAL REFLECTION.
•
All of the energy stays inside the block.
19
Optical Fibres Optical Fibre
20
Refracting Periscope
21 115
Keyhole Surgery
A camera and remote-controlled surgical instruments are inserted into a small incision in the patient. There is less risk of infection and a quicker recovery time than invasive surgery.
22
Fibre Optic Transmission
Signals are sent as pulses of light. Cheaper signal production, less signal boosting, more secure transmission, higher bandwidth (more information possible).
23
Converging Lens focus
focus
focal length
focal length
•
A convex (converging) lens is wider in the middle than at the edges.
•
Convex lenses have a principal focus on either side.
•
The distance between the lens and the focus is called the “focal length”
116
24
• Parallel light is converged to the focus. • Light entering through the focus emerges parallel.
• Light passing through the centre of the lens is unaffected.
25
Ray Diagrams • When drawing a ray diagram, we construct at least two rays from point on an object, and try to use the rules of converging lenses.
• The image is formed where the rays cross. • The Image can be magnified or reduced, further or closer, real or virtual, inverted or upright.
26
Problems •
Construct ray diagrams for the following:
•
A) An object of height 2cm placed 10cm from a convex lens of focal length 3cm.
•
B) An object of height 2cm placed 5cm from a convex lens of focal length 3cm.
•
C) An object of height 2cm placed 2.5cm from a convex lens of focal length 3cm.
27 117
The Electromagnetic Spectrum Long Wavelength
Short Wavelength
Low Frequency
High Frequency
Radio Waves
Micro Waves
Infra-red Waves
Visible
Ultraviolet Rays
X-Rays
Gamma Rays
28
Sound •
Sounds are produced when objects VIBRATE.
•
Sound is a LONGITUDINAL wave.
•
Reflected sound waves produce echoes.
•
Sound travels at about 340 m/s in air. It travels faster in liquids and faster still in solids.
•
Unlike light, sound needs a medium.
•
Sound waves can be displayed electronically using an Oscilloscope.
•
The greater the amplitude, the louder the sound.
•
The greater the frequency, the higher the pitch.
•
Our ears are sensitive to sound in the range 20 Hz - 20 kHz.
•
Ultrasound is of a higher frequency than our ears can detect. (pre-natal scans, sonar)
29
Sound Waves
Low Frequency (Low pitch) and Large Amplitude (Loud)
High Frequency (High pitch) and Large Amplitude (Loud)
Low Frequency (Low pitch) and Small Amplitude (Quiet)
High Frequency (High pitch) and Small Amplitude (Quiet)
30 118
Wave Physics Quantity and symbol Waves
Transverse Waves Longitudinal Waves Amplitude
Wave Speed, v
Wavelength, λ
Frequency, f Time Period, T
Refection Refraction
Refractive Index, n
Word equation / definition Waves transfer energy from one place to another without the mass movement of the medium itself. The oscillations are perpendicular to the direction of wave travel. Examples include; water waves, light, and any part of the electromagnetic spectrum. The oscillations are parallel to the direction of wave travel. Example is Sound. The amplitude of a wave is the maximum displacement of the particles from their equilibrium position. Speed is the rate of change of distance of the wave. It can be calculated using the speed/distance/time equation or, Speed = frequency x wavelength The distance between two adjacent crests, or two adjacent troughs. Or the distance between to adjacent points on a wave that are in the same phase of motion. Wavelength = speed frequency The number of waves passing a point in 1 second, or the number of oscillations of a particle or the source in 1 second Frequency = speed wavelength The time for one complete wave to pass a point or the time for one complete oscillation of a particle Time Period =_____1________ frequency The angle of incidence is equal to the angle of reflection. Refraction is the change of direction that occurs when waves enter, at an angle other than 90o, a medium in which it travels at a different speed. Refractive index is the ratio of the sine of angle of incidence to the sine of the angle of refraction (Snell’s Law) or the ratio of the speed of light in air or a vacuum to the speed of light in the medium. or the ratio of the real depth to the apparent depth
Symbol equation
units
cm m v=fλ
cm/s m/s
λ=v f
m
f=v λ
Hertz, Hz
T = _1_ f seconds i=r
n = sin i sin r n=c v n=R A
No units, it’s a ration
1 119
Critical Angle, C
Total Internal Reflection Diffraction Dispersion
Speed of Light Monochromatic
The Critical Angle occurs inside the more dense medium and is the angle of incidence, at which the angle of refraction is 90o, i.e. along the boundary between the mediums Total internal reflection occurs at angles greater than the critical angle inside a more dense medium. Diffraction is the spreading out of waves as they pass through a gap. The narrower the gap the more diffraction there is. Dispersion is the splitting of light into the colours of the spectrum, due to the different speeds at which these colours travel in the prism. And all other waves in the electromagnet spectrum Monochromatic means of one frequency. Therefore if monochromatic light is passed through a triangular prism dispersion will not occur.
Speed of Sound
n = ___1___ sin C
3.0 x108
m/s
330
m/s
2 120
iGCSE Physics Past Paper Questions Paper 1 Compilation Waves
121
heat
heat
9
19 The diagrams show part of a water-heating system which is working by convection. 20 1. A drop of water from a tap falls onto the surface of some water of constant depth. Which diagram shows the most likely flow of water in the system? A
B
hot water tank
hot water tank view from above
boiler
heat Water waves spread out on the surface of the water. Which statement is true? C A B C D
boiler
heat
D
The waves are longitudinal and travel at the same speed in all directions. hot hot water water The waves are longitudinal and travel more quickly in one direction than in others. tank tank The waves are transverse and travel at the same speed in all directions. The waves are transverseboiler and travel more quickly in one direction thanboiler in others.
heat 25 2. A girl stands in front of a rock face.
12
heat [Turn over
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20 A drop of water from a tap falls onto the surface of some water of constant depth. rock face
660 m
view from above
Water waves spread out on the surface of the water. Which statement is true? A
The waves are longitudinal and travel at the same speed in all directions.
claps her hands once. The speed of quickly sound in 330 m / s.than in others. B The Thegirl waves are longitudinal and travel more in air oneis direction C How The long waves transverse and the travel at the same speed in all directions. is itare before she hears echo? D
The waves are transverse and travel more quickly in one direction than in others. 2 x 660 660 330 330 ______ ___ s ___ s ______ A s s B C D
330
330
660
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2 x 660
26 Which diagram best shows the pattern of field lines around a bar magnet?
122
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10 213. A student measures how far a cork moves up and down on a wave in a tank of water. ruler
cork direction of wave
Which quantity can he obtain from his measurement? A
amplitude
B
frequency
C
speed
D
wavelength
4. Alpha-particles, beta-particles, gamma-rays and infra-red radiation may all be emitted from a 22 solid. Which of these are included in the electromagnetic spectrum? A
alpha-particles and beta-particles
B
alpha-particles and gamma-rays
C
beta-particles and infra-red radiation
D
gamma-rays and infra-red radiation
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11 235. The image of a clock face as seen in a plane mirror is shown.
21
3
9
6 What is the actual time on the clock? A
1.25
B
C
1.35
10.25
D
10.35
6. Four sound waves W, X, Y and Z are displayed by an oscilloscope screen. The oscilloscope 24 settings are the same in each case.
W
X
Y
Z
Which two sounds have the same pitch? A
W and X
B
W and Y
C
X and Y
D
X and Z
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10 227. Which statement is correct about the speed of electromagnetic waves in a vacuum? A
Ultra-violet waves have the greatest speed.
B
Visible light waves have the greatest speed.
C
Infra-red waves have the greatest speed.
D
All electromagnetic waves have the same speed.
23 Which diagram correctly shows rays passing through a camera lens? camera
A
camera
B film
film
object
object lens
lens
image
camera
C
image
camera
D film
film
object
object lens
lens
image
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image
11 248. A sound wave passes through the air, in the direction shown. → direction of travel of sound wave
How does a particle of air move as the sound wave passes? A
moves to the right and stays there
B
moves left and right
C
moves up and stays there
D
moves up and down
•→ ←•→ ↑ • ↑ • ↓
259. A boy is stranded on an island 500 m from the shore.
500 m
cliffs
island
He shouts for help, but all he can hear in reply is the echo of his shout from some cliffs. Sound travels at 340 m / s through the air. What is the time interval between the boy shouting and hearing the echo? A
500 s 340
B
2 × 500 s 340
C
340 s 500
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D
2 × 340 s 500
[Turn over
10
10. Water waves change direction when they move from shallow water to deep water. 20 new wave direction original wave direction deep water shallow water
What is the name of this effect? A
diffraction
B
dispersion
C
reflection
D
refraction
11. A vertical stick is dipped up and down in water at P. In two seconds, three wave crests are 21 produced on the surface of the water.
Y wave crests
P
X
Which statement is true? A
Distance X is the amplitude of the waves.
B
Distance Y is the wavelength of the waves.
C
Each circle represents a wavefront.
D
The frequency of the waves is 3 Hz.
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11
12. A plane mirror is on a wall. 22 Which is a correct description of the image formed by the mirror? A
the right way up and smaller than the object
B
the right way up and the same size as the object
C
upside down and smaller than the object
D
upside down and the same size as the object
23 13. The diagram shows a ray of light entering a block of glass. normal ray of light 2 air glass
1 3 4
Which numbered angles are the angles of incidence and of refraction? angle of incidence
angle of refraction
A
1
3
B
1
4
C
2
3
D
2
4
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14. Thre e rays of light fall on a converging lens as shown. 24
lens Which diagram shows the path of the rays after passing through the lens?
A
B
C
D
15. Which type of wave c a n n ot travel through a vacuum? 25 A
infra-red radiation
B
microwaves
C
sound waves
D
X-rays
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9 19 The diagram shows a block of ice placed in a warm room. 13 At which point is the temperature the lo w e st? 16. An engineer standing at P hears the sound of an explosion at X. 26 $ !
P clamp
ice
table
#
Z "
Y
X
DANGER BLASTING
V
W
20 The drawing shows a wave. After thelabelled explosion, she is hears two bangs. One bang is heard a fraction of a second after the Which distance the wavelength? other. The second bang is an echo from A A XY. B
PV.
C
ZY.
D
WX.
B
D C
17. 21 R adio waves are received at a house at the bottom of a hill. 27 How can a permanent magnet be demagnetised? A
cool the magnet for a long time
B
hit the magnet repeatedly with a hammer
C
leave the magnet in a coil which carries direct current
D
hill pass a small current through the magnet
28 An electromagnet is used to separate magnetic metals from non-magnetic metals. The waves re ach the house because the hill has caused them to be Why is steel unsuitable as the core of the electromagnet? A diffracted. AB Itradiated. is a good conductor of electricity. BC Itreflected. forms a permanent magnet. CD Itrefracted. has a high density. D It has a high thermal capacity.
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[T urn o v er
[T urn o v er
10
18. Which diagram correctly shows a ray of light passing through a rectangular glass block? 22 A
B
C
D
23 The ray diagram shows how an image is formed by a converging lens. 19. 9
24 cm
10 cm
8 cm
19 The diagram shows a block of ice placed in a warm room. At which point is the temperature the lo w e st? $ ! clamp
ice
table
"
#
What is the focal length of this lens? A
8 cm
B
10 cm
C
18 cm
D
20 The drawing shows a wave. 20. Which labelled distance is the wavelength?
A B
D C
21 Radio waves are received at a house at the bottom of a hill.
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24 cm
11
21. 24 A fire alarm is not loud enough. An engine er adjusts it so that it produces a note of the same pitch which is louder.
What effect does this have on the amplitude and on the frequency of the sound? amplitude
frequency
A
larger
larger
B
larger
same
C
same
larger
8
19 Two cups are placed D plastic same sameone inside the other. Hot water is poured into the inner cup and a lid is put on top as shown. lid 22. To estimate the width of a valley, a climber starts a stopwatch 25 as he shouts. H e he ars an echo from the opposite side of the valley after 1.0 s. small spacer small air gap
sound
hot water
climber
Which statement is correct?
bench
valley
A sound H e at loss by radiation The travels at 340 m /iss.prevented by the small air gap. B No he at passes through the sides of either cup. What is the width of the valley? C The bench is he ated by convection from the bottom of the outer cup. B 170 m C 340 m D 680 m A 85 m D The lid is used to reduce he at loss by convection. 26 Which material is used for the core of an electromagnet? 23. Which is the best description of the spe ed of a water wave? 20 A aluminium A the distance betwe en one wave crest and the next B copper B the distance betwe en the crest of a wave and a trough C iron C the distance that a particle of water moves up and down in one second D ste el D the distance that a wavefront moves along the surface in one second
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9
24. Water waves travel more slowly in shallow water than in deep water. 21 Which diagram shows what will happen to plane waves in deep water when they enter shallow water?
A deep
B shallow
deep
D
C deep
shallow
deep
shallow
shallow
22 25. A ray of light passes through a window. Which path does it take? air
glass
air
A B C D
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10
26. The diagram shows the image of a clock in a plane mirror. 23
What time is shown? A
02:25
B
02:35
C
09:25
D
09:35
24 27. The diagram shows a man standing at X who shouts to a man standing at Y.
X N
W
E S
Y The man’s voice will be heard sooner and more clearly if the wind is blowing towards the A
north.
B
south.
C
east.
D
west.
25 Sounds are made by vibrating objects. A certain object vibrates but a person nearby cannot hear any sound.
28. Which statement might explain why nothing is heard? A
The amplitude of the sound waves is too large.
B
The frequency of the vibration is too high.
C
The sound waves are transverse.
D
The speed of the sound waves is too high.
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B
convection
C
evaporation
D
radiation
9
19 The diagram shows a heater used to heat a tank of cold water. 29.20 What causes refraction when light travels from air into glass? A
The amplitude of the light waves changes.
B
The colour of the light changes.
C
The frequency of the light waves changes.
D
The speed ofwater the light changes.
lagging 30. A woman tunes her radio to a station broadcasting on 200 m. 21 tank What does the 200 m tell her about the radio wave? heater A its amplitude B
its frequency
C its speed What is the main process by which heat moves through the water? D its wavelength A
conduction
B
convection
C
evaporation
D
radiation 0625/01/M/J/03
20 What causes refraction when light travels from air into glass? A
The amplitude of the light waves changes.
B
The colour of the light changes.
C
The frequency of the light waves changes.
D
The speed of the light changes.
[Turn over
21 A woman tunes her radio to a station broadcasting on 200 m. What does the 200 m tell her about the radio wave? A
its amplitude
B
its frequency
C
its speed
D
its wavelength
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iGCSE Physics Past Paper Questions Paper 3 Compilation Waves
136
7 5 1. Fig. 5.1 shows an arrangement where a plane mirror is used in a shop to watch a display counter. The arrangement is drawn to a scale of 1 cm : 1 m.
For Examiner’s Use
plane mirror
P
wall display counter
Fig. 5.1 (a) (i)
State the law of reflection. ...................................................................................................................................
(ii)
On Fig. 5.1, draw rays to show how much of the display cannot be seen from P. Indicate this by shading in the part that cannot be seen. [3]
(b) By construction on Fig. 5.1 and by using the scale, calculate how far the mirror must be moved so that all of the display counter can be seen from P.
distance moved = .................................... [2] (c) State the characteristics of an image seen in a plane mirror. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2]
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For Examiner’s Use
8 62. Observations of a distant thunderstorm are made. (a) During a lightning flash, the average wavelength of the light emitted is 5 × 10–7 m. This light travels at 3 × 108 m/s. Calculate the average frequency of this light.
frequency = ...................................... [2] (b) The interval between the lightning flash being seen and the thunder being heard is 3.6 s. The speed of sound in air is 340 m/s. (i)
Calculate the distance between the thunderstorm and the observer.
distance = ............................................ (ii)
Explain why the speed of light is not taken into account in this calculation. ................................................................................................................................... ................................................................................................................................... [3]
(c) A single ray of white light from the lightning is incident on a prism as shown in Fig. 6.1. prism
screen ray of light
Fig. 6.1 Complete the path of the ray to show how a spectrum is formed on the screen. Label the colours. [2]
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7
For Examiner’s Use
63. Fig. 6.1 shows wavefronts of light crossing the edge of a glass block from air into glass.
air direction in which wavefronts are moving glass
edge of glass Fig. 6.1 (a) On Fig. 6.1 (i)
draw in an incident ray, a normal and a refracted ray that meet at the same point on the edge of the glass block,
(ii)
label the angle of incidence and the angle of refraction,
(iii)
measure the two angles and record their values. angle of incidence = .................................. angle of refraction = .................................. [4]
(b) Calculate the refractive index of the glass.
refractive index = ..................................[3]
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8
For Examiner’s Use
74. In a thunderstorm, both light and sound waves are generated at the same time. (a) How fast does the light travel towards an observer? speed = ..................................
[1]
(b) Explain why the sound waves always reach the observer after the light waves. ......................................................................................................................................[1] (c) The speed of sound waves in air may be determined by experiment using a source that generates light waves and sound waves at the same time. (i)
Draw a labelled diagram of the arrangement of suitable apparatus for the experiment.
(ii)
State the readings you would take. ................................................................................................................................... ................................................................................................................................... ...................................................................................................................................
(iii)
Explain how you would calculate the speed of sound in air from your readings. ................................................................................................................................... ................................................................................................................................... [4]
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8 65. Fig. 6.1 shows a ray PQ of blue light incident on the side of a rectangular glass block.
A
B
glass
C Q
D
air
Fig. 6.1
P
Fig. 6.1 (a) (i) (ii)
By drawing on Fig. 6.1, continue the ray PQ through and beyond the block. Mark the angle of incidence at CD with the letter i and the angle of refraction at CD with the letter r. [3]
(b) The speed of light in air is 3.0 x 108 m/s and the speed of light in glass is 2.0 x 108 m/s. (i)
Write down a formula that gives the refractive index of glass in terms of the speeds of light in air and glass. refractive index =
(ii)
Use this formula to calculate the refractive index of glass. refractive index = ………………… [2]
(c) The frequency of the blue light in ray PQ is 6.0 x 1014 Hz. Calculate the wavelength of this light in air.
wavelength = ……………..……[2] © UCLES 2004
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For Examiner’s Use
9 76. Fig. 7.1 shows the cone of a loudspeaker that is producing sound waves in air. At any given moment, a series of compressions and rarefactions exist along the line XY.
For Examiner’s Use
cone
X
Y
wires air
Fig. 7.1 (a) On Fig. 7.1, use the letter C to mark three compressions and the letter R to mark three rarefactions along XY. [1] (b) Explain what is meant by (i)
a compression, ................................................................................................................................... ...................................................................................................................................
(ii)
a rarefaction. ................................................................................................................................... ................................................................................................................................... [2]
(c) A sound wave is a longitudinal wave. With reference to the sound wave travelling along XY in Fig. 7.1, explain what is meant by a longitudinal wave. .......................................................................................................................................... ......................................................................................................................................[2] (d) There is a large vertical wall 50 m in front of the loudspeaker. The wall reflects the sound waves. The speed of sound in air is 340 m/s. Calculate the time taken for the sound waves to travel from X to the wall and to return to X.
time = …………………[2]
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9 67. Fig. 6.1 shows a ray of light OPQ passing through a semi-circular glass block.
For Examiner’s Use
O
P
30°
Q
Fig. 6.1 (a) Explain why there is no change in the direction of the ray at P. .......................................................................................................................................... ..................................................................................................................................... [1] (b) State the changes, if any, that occur to the speed, wavelength and frequency of the light as it enters the glass block. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (c) At Q some of the light in ray OPQ is reflected and some is refracted. On Fig. 6.1, draw in the approximate positions of the reflected ray and the refracted ray. Label these rays. [2] (d) The refractive index for light passing from glass to air is 0.67. Calculate the angle of refraction of the ray that is refracted at Q into air.
angle = ………………. [3]
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10 78. Fig. 7.1 shows the parts of the electromagnetic spectrum.
ultraviolet
γ - rays and X - rays
v i s i b l e
infrared
For Examiner’s Use
radio waves
Fig. 7.1 (a) Name one type of radiation that has (i)
a higher frequency than ultra-violet, .............................................................................................................................. [1]
(ii)
a longer wavelength than visible light. .............................................................................................................................. [1]
(b) Some γ-rays emitted from a radioactive source have a speed in air of 3.0 x 108 m/s and a wavelength of 1.0 x 10–12 m. Calculate the frequency of the γ-rays.
frequency = ………………. [2] (c) State the approximate speed of infra-red waves in air. ..................................................................................................................................... [1]
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7 69. Fig. 6.1 shows white light incident at P on a glass prism. Only the refracted red ray PQ is shown in the prism.
P red ray Q
t
white ligh
screen
Fig. 6.1 (a) On Fig. 6.1, draw rays to complete the path of the red ray and the whole path of the violet ray up to the point where they hit the screen. Label the violet ray. [3] (b) The angle of incidence of the white light is increased to 40°. The refractive index of the glass for the red light is 1.52. Calculate the angle of refraction at P for the red light.
angle of refraction = ........................[3] (c) State the approximate speed of (i)
the white light incident at P,
speed = ........................ [1]
(ii)
the red light after it leaves the prism at Q.
speed = ........................ [1]
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For Examiner’s Use
8 710. Fig. 7.1 shows how the air pressure at one instant varies with distance along the path of a continuous sound wave. air pressure
normal P air pressure
X
Y distance in direction of travel of the wave
Fig. 7.1 (a) What type of waves are sound waves? ......................................................................................................................................[1] (b) On Fig. 7.1, mark on the axis PY (i)
one point C where there is a compression in the wave,
[1]
(ii)
one point R where there is a rarefaction in the wave.
[1]
(c) Describe the motion of a group of air particles situated on the path of the wave shown in Fig. 7.1. .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[2] (d) The sound wave shown has speed of 340 m / s and a frequency of 200 Hz. Calculate the distance represented by PX on Fig. 7.1.
distance = ........................[2]
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For Examiner’s Use
Topic 4: Electricity & Magnetism
1
Charge •
Charge is a property that objects can have.
•
Charge can be positive (+) or negative (-).
•
Charge is measured in coulombs (C).
•
Conductors allow charge to move (metals & graphite).
•
Insulators prevent charge from moving (Most non-metals).
•
Electrons are usually responsible for movement of charge (current).
2
Charging by Friction •
When two insulators are rubbed together, ELECTRONS are transferred from one to the other and the objects become charged.
•
This is called charging by friction because friction is the force that moves the electrons.
•
Only electrons move. Positive charge does not move.
3 147
Polythene Rods •
Polythene rods gain a negative charge when rubbed with a cloth.
•
Electrons are moved from the cloth to the rod.
•
The cloth becomes positively charged.
4
Perspex Rods •
Perspex rods gain a positive charge when rubbed with a cloth.
•
Electrons are moved from the rod to the cloth.
•
The cloth becomes negatively charged.
5
The Gold-Leaf Electroscope Metal Cap Metal Rod
Metal Case
Insulator Gold Leaf
•
The Gold-Leaf electroscope is an instrument that detects and measures electrostatic charge.
•
It consists of a metal (conductor) cap and rod with a thin piece of gold foil (conductor) connected.
•
The rod is held in place by plastic (insulator).
•
The earthed outer case is made from metal (conductor).
6 148
The Law of Electrostatics •
If charged objects are placed beside each other, they experience a force.
•
The force depends upon the charges on the objects.
•
An electric field surrounds the charges. This is a region of influence on other charges. repel
repel
attract
attract
7
The Law of Electrostatics •
This can be summarised as:
Opposite Charges Attract. Like Charges Repel.
8
Summary of Quantities Quantity
Symbol
Unit
Unit’s Symbol
Current
I
Ampere
A
Potential Difference (Voltage)
V
Volt
V
Resistance
R
Ohm
Ω 9 149
Current/Voltage Graphs •
The characteristics of a component can be shown by graphing the current through it for varying voltages.
•
This graph is called the characteristic of the component.
•
Negative p.d.s are plotted as well as positive ones.
10
Ohmic Resistors •
Ohmic resistors have a proportional relationship between current and pd. This is because the resistance remains constant for all voltages. current
p.d.
11
Filament Lamp •
A filament lamp or standard resistor does not ‘behave itself ’ as well as an ohmic resistor. The resistance increases with voltage as the wire gets hotter. current
p.d.
12 150
The Diode •
The diode’s behaviour depends upon its direction in the circuit. It allows current to flow in the positive direction but blocks it in the negative direction. It can be thought of as an electric valve. current
p.d. 0.7 V
13
Ohm’s Law •
Ohm’s Law states that the current in, and voltage across a conductor are proportional provided that the temperature and other physical quantities remain the same.
•
This is easily seen in an ohmic resistor.
14
Potential Difference in Series Circuits • In a series circuit the PD from the cell (Vt) is divided among the individual components: Vt
V1
V2
Vt = V1 + V2 + ...
15 151
Current in Series Circuits • In a series circuit the Current is the same at all points in the circuit. This is because of the conservation of charge. It
It
I2
I1
I t = I1 = I 2 = ...
I3
16
Resistance in Series Circuits • The Combined Resistance (Rt) is equal to the sum of the individual resistances:
Rt = R1 + R2 + ...
Rt
R1
R2
17
Potential Difference in Parallel • In a Parallel circuit the PD across each strand is the same as the PD supplied to the strand since the voltage is between the same two points in each case. Vt
V1
Vt = V1 = V2 = ...
V2
18 152
Current in Parallel Circuits • In a Parallel circuit the current supplying the strands splits. Because of the conservation of charge:
It
I t = I1 + I 2 + ...
I1
I2
19
Resistance in Parallel • In a parallel combination, the combined resistance is found using the following equation:
Rt
1 1 1 = + + ... Rt R1 R2
R1 R2
20
Resistance • Electric Current is opposed by components in a circuit. This opposition is called Resistance.
• Resistance can be defined by the equation: R(Ω) =
V (V ) I(A)
21 153
Current •
Current is the rate at which charge (coulombs) passes a point in a circuit.
•
Current is measured with an ammeter in a circuit which is placed in series at the point where the current needs to be measured.
I(A) =
Q(C) t(s)
22
Potential Difference •
Electrical Energy is given to the charges in a cell (battery). This energy is given up in the components.
•
Both cells and components in a circuit have a voltage across them.
•
Potential Difference is measured in a circuit with an voltmeter. It should be placed in parallel across the two points where the PD is to be found.
V (V ) =
ΔEnergy(J ) Q(C)
23
The Potential Divider Vt
I
V1=IR1
V2=IR2
• The total PD across the resistors is shared by the resistors.
• The share of the voltage that each resistor gets depends upon its resistance.
• If R1 is large compared to R2 then it will have a much bigger share of the voltage across it.
24 154
Simpler Design Vt
I
V1
• The Potential Divider can be made adjustable by using a variable resistor and taking a voltage from the rheostat.
25
Task • Using the 12V setting on the power pack, a variable resistor, a voltmeter a bulb and leads, construct a circuit that supplies the bulb with exactly 4.56 V.
V
26
Energy in D.C. Circuits It has been shown that Voltage is the Work Done per Coulomb But we also know that: So:
V=
I=
Q = It Energy = VQ
WD Q
Q t
Energy = VIt 27 155
Power in D.C. Circuits Power =
Since
ΔEnergy t
Energy = VIt
and
Power =
so
VIt t
Power = VI 28
Combining Ohms Law Equation Since P=VI, we can use V=IR to get alternative expressions for Power:
P = VI
P=I R 2
V2 P= R
29
Conductors •
Increasing the temperature of a conductor will increase its resistance since this will lead to more electron collisions.
30 156
Semiconductors
• Silicon is a semiconductor. Its electrons are held
tightly so it is a poor conductor of electricity. Increasing the energy to the electrons can free them, and the silicon becomes a better conductor.
• This energy can be provided from light (an LDR) or heat (a Thermistor).
31
The Transistor collector base emitter
• A transistor is an electronic component. • It is often used as a switch. • The base-emitter current (small) controls the collector-emitter current (large).
• It can be compared to “opening a gate”.
Transistor
32
+6V
0V As the temperature drops, the resistance of the thermistor ................... The voltage across b-e will.................... and the transistor is switched-on and the bulb lights. Possible Use:
33 157
Transistor
+6V
0V As the temperature rises, the resistance of the thermistor ................... The voltage across b-e will.................... and the transistor is switched-on and the bulb lights. Possible Use:
34
Transistor +6V
0V As the light level drops, the resistance of the LDR ................... The voltage across b-e will.................... and the transistor is switched-on and the bulb lights. Possible Use:
35
Transistor
+6V
0V As the light level rises, the resistance of the LDR ................... The voltage across b-e will.................... and the transistor is switched-on and the bulb lights. Possible Use:
36 158
The Diode •
The Diode is an electronic ‘valve’.
•
It allows current to flow one way but not the other.
37
The Capacitor •
A capacitor charges-up when a current flows, and discharges when the current is removed.
•
Because this takes time to happen, they are often used in electronics to control timed events.
38
Rectification Circuit A.C. Input
D.C. Output
•
The Diode removes any current flowing in the reverse direction.
•
The Capacitor charges up and discharges to smooth the output.
39 159
A.C Voltage
Half-Wave Rectified Half-Wave Rectified and Smoothed 40
Digital vs Analogue Signals •
Analogue signals are continuously varying.
•
Digital signals are pulses (on, off). They contain data as binary digits.
•
Computers process ONLY digital signals.
41
Electronic Systems •
There are three stages to an electronic system:
•
INPUT Transducers - Create digital information.
•
PROCESS - Manipulate or compare information.
•
OUTPUT Transducers - Use the result of the process.
42 160
NOT Gate
A
A 0 1
B
B 1 0
43
OR Gate
A
C
B
A
B
C
0
0
0
0
1
1
1
0
1
1
1
1
44
AND Gate
A C B
A
B
C
0
0
0
0
1
0
1
0
0
1
1
1
45 161
Tasks •
Build an alarm clock for a deaf person that will light up at dawn.
•
Build a eco-friendly device that would tell you if your pool was too cold for swimming. The device should light up when you press a button.
•
Build a device that will sound an alarm at Isha. It must activate a buzzer when it is dark and the device is switched on.
•
Build a fire alarm that activates a buzzer and a warning light when it gets too hot. The alarm should have a test button for the battery.
46
Production of a Cathode Ray Anode
H Heating Element
Cathode
Vacuum
•
The heating element ‘boils’ the excess electrons off the cathode.
•
Most of the electrons hit the Anode, but some pass through the gap in a high speed Cathode Ray.
47
The Electron Gun •
A television produces a picture by focusing a cathode ray onto a screen that glows when the beam hits it.
•
Computer monitors and Cathode Ray Oscilloscopes (CROs) also use this idea.
•
X-Ray generators also use cathode rays.
48 162
Uses of Cathode Rays
49
Magnets • There are two types of magnetic pole, North and South.
• Fields run from North to South and can be shown with iron filings.
• Magnets attract magnetic materials. • Ferrous materials (containing iron) are often magnetic, especially steel.
• Magnetic materials can have magnetism induced. This is called ‘magnetising’.
• Pure iron loses its magnetism easily.
50
Magnetising and Demagnetising •
•
Methods of magnetising include:
•
Stroking
•
Field induction (DC Coil)
Methods of demagnetising include
•
Heating
•
Hammering
•
AC coil
51 163
Permanent Magnets vs Electromagnets •
Permanent magnets keep their magnetism and need no power source. Their strength not easy to control.
•
Electromagnets need current to keep their magnetism. Their strength is easy to control.
52
Field Around a Current Carrying Wire If a current is passed through a wire, a circular magnetic field is generated around the wire.
53
Field Around a Current Carrying Wire If the current is reversed, the direction of the magnetic field is reversed.
54 164
Right-Hand Grip Rule •
The Right-Hand Grip allows us to predict the direction of the circular field lines around a wire.
•
The thumb of the right hand points in the direction of CONVENTIONAL current.
•
The fingers show the direction of the circular field.
55
Field Around a Loop
If the wire is bent into a loop, the magnetic field will run through the middle of the loop.
56
Magnetic Field in a Coil. In a Solenoid, the Magnetic field from each loop adds to give a strong magnetic field through the middle of the coil.
57 165
Field Around a Coil The magnetic field around a solenoid is similar to that of a bar magnet.
58
The Relay •
A relay is a device that uses electromagnetism to allow a small current to switch-on a large current.
•
When the small current flows, the solenoid becomes magnetised and a switch is activated.
iron
small current
large current starter motor
spring
59
The Reed Relay •
Another variation on the relay involves two strips of metal (reeds) placed side by side. One is iron, and one is nonmagnetic.
•
When the current flows, the magnetic reed makes contact with the non-metal. small current large current non-magnetic reed
magnetic reed
60 166
The Motor Effect •
If a current is placed in a magnetic field, the wire is forced out.
S
N
61
The Motor Effect •
If a current is placed in a magnetic field, the wire is forced out.
N
S
62
Left Hand Rule •
To predict the direction of the movement we use Fleming’s Left-hand rule.
First finger - Field seCond finger - Current thuMb - Movement
63 167
The DC Motor • If we pass a current through a loop of wire, and
place it in a magnetic field, we get forces due to the motor effect.
S
N
commutator
64
Design Improvements •
Increasing the supply voltage (current) increases the strength of the motor.
•
Increasing the strength of the magnetic field increases the strength of the motor.
•
Adding more loops increases the strength of the motor.
65
Induction •
Electromagnetic Induction can be seen as the opposite to the Motor Effect. Electrical Energy
Motor Effect
Kinetic Energy
Kinetic Energy
Induction
Electrical Energy
G
A current is induced when the magnet is moved through the coil, but no current is induced when the magnet is stationary.
66 168
Induced Current •
If the wire is pushed downwards, it will cut field lines and a current will be induced into the page as shown.
S
• •
N
The faster the relative movement, the stronger the current. If the movement is reversed, the current is reversed.
67
Generating AC •
If a coil spins in a magnetic field, an AC Voltage is induced.
S
N
68
Uses of Induction •
Microphone
•
Bicycle Dynamo
•
Power Station Generator
69 169
Transformer Overview •
The transformer consists of a ring of laminated magnetic material (Iron) with two circuits attached.
•
An AC current in the Primary Circuit induces a changing magnetic field in the iron.
•
This field in turn induces an AC current in the Secondary Circuit.
70
Primary Circuit (AC)
NP
NS
Secondary Circuit (AC) VS
VP
71
Transformer Equation • If the number of coils increase, we have a step-up transformer and the voltage increases in the same ratio.
• If the number of coils decrease, we have a stepdown transformer and the voltage decreases in the same ratio.
• This gives the following relationship: VS N S = VP N P
72 170
Energy Considerations • Since Power in a circuit is given by P=VI, we can calculate the electrical power in the primary and secondary circuits:
PP = VP I P
PS = VS I S
• If we assume the transformer to be 100% efficient, we have:
VP I P = VS I S 73
171
Electricity and Magnetism Quantity and symbol
Word equation / definition
Symbol equation
Charge = current x time Q=It The charge on one electron is 1.6 x 10-19 An electric field is a region in which an electric charge experiences a force. The Electric Field direction of the field is the direction in which a positive test charge would move. The electro-motive force, or E.M.F., is Electro-motive defined as the amount of energy supplied by force, E, E.M.F., a source in driving charge around a complete e.m.f. circuit. The potential difference is the energy Potential Difference, difference per coulomb of charge that the 1 V = 1 J/C p.d.,V current is carrying before and after a component. Current is the rate of flow of charge. I=Q Conventional current is from positive to Current, I negative. This is the opposite direction to the t flow of electrons. Resistance is a property of a material that R=V opposes the flow of current. Resistance, R Resistance = potential difference I current Resistance is directly proportional to the length of a piece of wire, for constant Resistance, R RαL temperature and cross-section area. Resistance is indirectly proportional to the Rα1 cross-section area of a piece of wire, for Resistance, R constant temperature and length. Material A and temperature also affect the resistance. The current in a series circuit is the same at every point. The sum of the p.d.’s across the Series Circuits components in a series circuit is equal to the total p.d. across the supply. The current from the source is the sum of the currents in the separate branches of a parallel Parallel Circuits circuit. The p.d.’s across each parallel branch in a parallel circuit is the same. Total resistance = the sum of the resistors in Resistors, in series RT = R1 + R2 series The combined resistance of 2 resistors in 1 1 1 Resistors, in parallel parallel is less than that of either resistor by RT = R1 + R2 itself. Electrical Energy, E Electrical energy = potential difference x E=VIt current x time Electrical Power, P Electrical power = potential difference x P=IV Charge, q, Q
units Coulombs, C, As
V
V mV A mA Ohms Ω Ohms Ω Ohms Ω
Ohms Ω Ohms Ω Joules, J Watts, W
1 172
Electromagnetic Induction Transformer, (for 100% efficiency)
The Motor Effect
Thermionic Emission
current Or Electrical power = potential difference2 resistance Or Electrical power = current2 x resistance A changing magnetic field can induce a e.m.f. in a closed circuit. The direction of the induced e.m.f. opposes the change causing it. Ratio of the potential difference in the primary coil to the secondary coil is equal to the ratio of the number of turns on the primary to the secondary, and equal to the ratio of the current in the secondary to the current in the primary A current carrying wire in a magnetic field experiences a force. The direction of that force can be worked out using Fleming’s Left Hand Rule. A heated piece of metal will release electrons.
P = V2 R P = I2R
np/ns = Vp/Vs =Is/Ip
No units, it’s a ratio
2 173
iGCSE Physics Past Paper Questions Paper 1 Compilation Electricity & Magnetism
174
15 12
1. When electricity is transmitted over long distances, energy is wasted. How can the wasted 34 25 energy A girl stands of as a rock face. be keptinasfront small possible? A
Keep the current in the transmission lines as large as possible.
B
rock face Keep the power supplied to the transmission lines as large as possible.
C
Keep the resistance of the transmission lines as large as possible.
D
Keep the voltage supplied to the 660 m transmission lines as large as possible.
352. The diagram shows a transformer. 300 turns
30 turns 12 V a.c.
V
a.c. voltmeter
The girl claps her hands once. The speed of sound in air is 330 m / s. What is the voltmeter reading? How long is it before she hears the echo? A 1.2 V B 12 V C 120 V D 1200 V A
2 x 660 ______ s 330
B
660 ___ s 330
C
330 ___ s 660
D
330 ______ s 2 x 660
26 3. Which diagram best shows the pattern of field lines around a bar magnet? A
N
B
S
N
C
N
S
D
S
N
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S
[Turn over
13 274. Which materials are suitable to make a permanent magnet and the core of an electromagnet? permanent magnet
core of an electromagnet
A
iron
iron
B
iron
steel
C
steel
iron
D
steel
steel
5. Which two electrical quantities are measured in volts? 28 A
current and e.m.f.
B
current and resistance
C
e.m.f. and potential difference
D
potential difference and resistance
6. Which of the following pieces of copper wire has the greatest electrical resistance? 29 length / m
diameter / mm
A
5.0
0.05
B
5.0
0.10
C
50
0.05
D
50
0.10
7. A 20 Ω resistor and a 10 Ω resistor are connected in parallel. 30
20 Ω 10 Ω What is their combined resistance? A
less than 10 Ω
B
10 Ω
C
20 Ω
D
more than 20 Ω
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14 318. The diagram shows an incomplete circuit. space A
Which component should be connected in the space to make the lamp light? A
B
C
D
329. Why are the electric lamps in a house lighting circuit normally connected in parallel? A
The current in every circuit must be the same.
B
The lamps are always switched on and off at the same time.
C
The voltage across each lamp must be the mains voltage.
D
When one of the lamps blows, all the others go out.
10. In the circuit shown, one of the fuses blows and all the lamps go out. 33 Which fuse blows? +
–
A
B
C D
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16
11. The diagram shows part of a circuit used to switch street lamps on and off automatically. 36 +
LDR – What is the effect on the light-dependent resistor (LDR) when it gets dark? resistance of LDR
p.d. across LDR
A
decreases
decreases
B
decreases
increases
C
increases
decreases
D
increases
increases
12. An alternating potential difference (p.d.) is applied to the Y-plates of a cathode-ray oscilloscope. 37 The time-base is turned off. Which of the following patterns would appear on the screen? A
B
C
38 What is a beta-particle? A
a helium nucleus
B
a high-energy electron
C
four protons
D
two neutrons
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D
12
13. A student wishes to use a magnetising coil to make a permanent magnet from a piece of metal. 26 metal
Which metal should she use? A
aluminium
B
copper
C
iron
D
steel
14. A metal rod XY is placed near a magnet. End X is attracted when it is placed near to the north pole 27 of the magnet, and also when it is placed near to the south pole. X
Y N
N attraction
X
Y
S
S
attraction How does end Y behave when it is placed, in turn, near to the two poles of the magnet? Y near north pole Y near south pole A
attraction
attraction
B
attraction
repulsion
C
repulsion
attraction
D
repulsion
repulsion
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13
15. When the potential difference (p.d.) across a piece of resistance wire is changed, the current 28 through the wire also changes. The temperature of the wire is kept the same. Which graph shows how the p.d. and current are related? A
B
current
0 0
C
current
current
0
p.d.
D
0
p.d.
0
current
p.d.
0
0
p.d.
0
16. Two faulty ammeters and two perfect ammeters are connected in series in the circuit shown. 29
A1
A2
A3
A4
The readings on the ammeters are A1 2.9 A A2 3.1 A A3 3.1 A A4 3.3 A Which two ammeters are faulty? A
A1 and A2
B
A1 and A4
C
A2 and A3
D
A3 and A4
17. Which electrical component would not normally be found in a battery-operated torch (flashlight)? 30 A
B
C
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D
[Turn over
14
18. A student connects two lamps in the circuit shown. 31
1
2 3
Which switches must he close to light both lamps? A
1 and 2
B
1, 2 and 3
C
1 and 3
D
2 and 3
32 19. A student makes four circuits. In which circuit are both lamps protected by the fuse? A
B
C
D
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15
20. Four lamps are labelled ‘60 W 240 V’. 33 In which circuit are the lamps connected so that they all work at normal brightness? A
B
C
240 V
240 V
240 V
D 240 V
21. The diagram shows a solenoid connected to a sensitive voltmeter. 34 S
magnet
N
solenoid V
Which of the following would give a zero reading on the voltmeter? A
holding the magnet stationary inside the solenoid
B
moving the magnet away from the solenoid
C
moving the magnet towards the solenoid
D
moving the solenoid towards the magnet
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21. The diagram shows a transformer with an alternating voltage of 100 V applied to the primary coil. 35
secondary coil
primary coil 100 V
(40 turns)
(80 turns)
What is the voltage produced across the secondary coil? A
B
50 V
100 V
C
D
200 V
8000 V
36 22. The diagram below shows the screen of a cathode-ray oscilloscope tube. spot of light
The tube is placed between a pair of charged plates. Which diagram shows the new position of the spot? A
B
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
C
D
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
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17
23. An electrical component X is placed in water, as shown. 37 13
A 26 An engineer standing at P hears the sound of an explosion at X. Z
P
thermometer
X
Y X
DANGER BLASTING
water
V
W
After sheof hears two isbangs. One the bang is heard a fraction of increases. a second after the Whenthe theexplosion, temperature the water increased, reading on the ammeter other.
What is component X? The second bang is an echo from AA
a capacitor XY.
BB CC
a light-dependent resistor PV. a reed relay ZY.
DD
a thermistor WX.
38 Which type of radiation can be stopped by a sheet of paper? 27 24. How can a permanent magnet be demagnetised? AA
α-particles cool the magnet for a long time
BB
β-particles hit the magnet repeatedly with a hammer
CC
γ-raysthe magnet in a coil which carries direct current leave
DD
X-rays pass a small current through the magnet
39 An half-life of a radioactive substance is 5 hours. A sample is tested and metals. found to contain 0.48 g 28 is used to separate magnetic metals from non-magnetic 25. Theelectromagnet of the substance. Why is steel unsuitable as the core of the electromagnet? How much of the substance was present in the sample 20 hours before the sample was tested? A It is a good conductor of electricity. A 0.03 g B It forms a permanent magnet. B 0.12 g C It has a high density. C 1.92 g D It has a high thermal capacity. D 7.68 g
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26. Which circuit shows how a voltmeter is connected to measure the potential difference across the 29 cell? A
V
B
C
11
V
D
V
24 A fire alarm is not loud enough. An engineer adjusts it so that it producesV a note of the same pitc which is louder. What effect does this have on the amplitude and on the frequency of the sound?
30 A polythene rod repels an inflated balloon hanging from a nylon thread. 27. amplitude What charges must the rod frequency and the balloon carry?
A B C D
A larger larger The rod and the balloon carry opposite charges. B larger same The rod and the balloon carry like charges. C same larger The rod is charged but the balloon is not. D same same The balloon is charged but the rod is not.
25 To estimate the width of a valley, a climber starts a stopwatch as he shouts. He hears an ech
31 Anfrom electrical component is of to be the 1.0 circuit 28. s. at Z, to allow the brightness of the lamp to the opposite side theplaced valley in after be varied from bright to dim. sound
climber
Z
valley
What should be connected at Z? The sound travels at 340 m / s. A B What is the width of the valley? V B 170 m A 85 m
C
C
340 m
26 29. Which material is used for the core of an electromagnet? A
aluminium
B
copper
C
iron
D
steel
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D
D
680 m
15
30. The circuit shown contains four lamps and thre e switches. 32
switch 1
lamp 1
switch 2
lamp 2 lamp 3
switch 3
lamp 4
Which switches must be closed to light only lamps 1 and 3? A
switch 1 only
B
switch 1 and switch 2 only
C
switch 1 and switch 3 only
D
switch 2 and switch 3 only
31. The diagram shows a torch containing two 2 V cells, a switch and a lamp. 33
plastic case brass connecting strip
switch lamp
What is the circuit diagram for the torch? A
U C L E S 2004
B
C
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D
[Turn over
16
32. Which statement is correct? 34 A
A fuse is included in a circuit to prevent the current becoming too high.
B
A fuse should be connected to the neutral wire in a plug.
C
An electric circuit will only work if it includes a fuse.
D
An earth wire is needed to prevent the fuse blowing.
33. A straight wire carrying a current produces a magnetic field. 35 Which diagram shows the correct shape of the field?
A
B
current
current
C
D current
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17
34. A student carries out an experiment to se e the effect of a magnetic field on a wire carrying a 36 current. The wire moves upwards as shown. wire moves upwards
N
S direction of current
What should the student do to make the wire move downwards? A
change the direction of the current
B
move the poles of the magnet closer together
C
send a smaller current through the wire
D
use a stronger magnet
35. A be am of cathode rays passes through an electric field betwe en two parallel plates. 37 + + + + + + cathode rays _ _ _ _ _ _
In which direction is the be am deflected? A
into the page
B
out of the page
C
towards the bottom of the page
D
towards the top of the page
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36. A brass rod is positioned in an east-west direction and a plotting compass is placed at each end. 27 brass rod N
plotting compass
Which diagram shows the positions of the needles of the plotting compasses? A
B
C
D
28 37. How many of the following materials conduct electricity? aluminium silver iron plastic A
1
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B
2
C
3
D
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4
13
38. In which circuit does the voltmeter read the potential difference across the lamp? 29 A
B
V
V
C
D
V
V
30 39. In the circuit below, X and Y are identical 6 V lamps. 6V switch
X
Y
What happens when the switch is closed? A
X lights more brightly than Y.
B
Y lights more brightly than X.
C
X and Y light with equal brightness.
D
Neither X nor Y light.
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40. The diagram shows a circuit with three ammeters, X, Y and Z. 31
A X A A
Y Z
Which set of readings is possible? X
Y
Z
A
2A
3A
5A
B
3A
2A
5A
C
3A
3A
3A
D
5A
2A
3A
41. A lamp is to be connected in a circuit so that the p.d. across it can be varied from 0 to 6 V. 32 Which circuit would be most suitable?
A
B
6V
6V
C
D
6V
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6V
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15 33 42. A student makes the circuit shown. 5 A fuse
The fuse has blown and stopped the current. What could have caused this? A
The current rating of the fuse was too high.
B
The current was too large.
C
The lamp was loose.
D
The voltage was too small.
34 43. Which graph shows the output voltage from a simple a.c. generator?
voltage A
0
time
voltage B
0
time
voltage C
0
time
voltage D
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0
time
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44. A transformer has 50 turns on its primary coil and 100 turns on its secondary coil. An a.c. voltage 35 of 25.0 V is connected across the primary coil.
25.0 V primary coil 50 turns
secondary coil 100 turns
What is the voltage across the secondary coil? A
12.5 V
B
50.0 V
C
175 V
D
200 V
45. Two circuits are set up as shown. The iron rods are placed close together, and are fre e to move. 36
S iron rod
X
iron rod
What happens to the siz e of the gap at X when switch S is closed? A
It decre ases.
B
It decre ases then incre ases.
C
It incre ases.
D
It does not change.
37 46. The diagram shows a simple cathode-ray tube. Which part emits the electrons? –
+
D A
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C
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11
47. A student investigates which end of a magnetic compass needle is attracted to a bar magnet. 26 What does the investigation show? A
Both ends of the compass needle are attracted by the north pole of the magnet.
B
Both ends of the compass needle are attracted by the south pole of the magnet.
C
One end of the compass needle is attracted by the north pole and the other end by the south pole.
D
The compass needle is not attracted by either end of the magnet.
27 From which materials are the coil and the core of an electromagnet made? 48. coil
core
A
copper
copper
B
copper
iron
C
iron
copper
D
iron
iron
28 49. What are the symbols used for the units of current and resistance? unit of current
unit of resistance
A
A
W
B
A
Ω
C
V
W
D
V
Ω
29 When a plastic comb is placed next to a small piece of aluminium foil hanging from a nylon 50. thread, the foil is repelled by the comb. Why is this? A
The comb is charged and the foil is uncharged.
B
The comb is uncharged and the foil is charged.
C
The comb and the foil have charge of opposite signs.
D
The comb and the foil have charge of the same sign.
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51. Which symbol represents an electrical component used to store energy? 30 A
B
C
D
31 52. F our lamps and four switches are connected to a power supply as shown in the circuit diagram. When all the switches are closed, all the lamps are lit. When one of the switches is then opened, only one lamp goes out. Which switch is opened?
A
B
C
D
53. F our resistors and an ammeter are connected to a battery as shown. 32 The ammeter re ads 2 A. Which of the four labelled points in the circuit is the only one where the current is less than 2 A?
A
A
C
B
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D
13
54. Why is a fuse used in an electrical circuit in a house? 33 A
to increase the circuit resistance
B
to keep the power used to a minimum value
C
to prevent a short-circuit from occurring
D
to stop the cables from carrying too much current
34 55. An electric power tool is being used outdoors in a shower of rain. What is the greatest hazard to the user? A
The cable gets hot and causes burns.
B
The circuit-breaker cuts off the current.
C
The current passes through water and causes a shock.
D
The tool rusts.
35 56. A current-carrying coil in a magnetic field experiences a turning effect.
variable power supply
N
S
How can the turning effect be increased? A
increase the number of turns on the coil
B
reduce the size of the current
C
reverse the direction of the magnetic field
D
use thinner wire for the coil
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57. A transformer is to be used to produce a 6 V output from a 24 V input. 36 coil X
coil Y
24 V
6V
What are suitable numbers of turns for coil X and for coil Y? number of turns on coil X
number of turns on coil Y
A
240
60
B
240
240
C
240
960
D
960
60
58. A cathode-ray tube has an anode and an earthed cathode. 37 Which line in the table shows the charge and the temperature of the anode? anode charge
anode temperature
A
negative
cool
B
negative
hot
C
positive
cool
D
positive
hot
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iGCSE Physics Past Paper Questions Paper 3 Compilation Electricity & Magnetism
198
9 71. (a) Two non-conducting spheres, made of different materials, are initially uncharged. They are rubbed together. This causes one of the spheres to become positively charged and one negatively charged.
For Examiner’s Use
Describe, in terms of electron movement, why the spheres become charged. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (b) Once charged, the two spheres are separated, as shown in Fig. 7.1.
+ + + + + + +
– – – – – – – Fig. 7.1
On Fig. 7.1, draw the electric field between the two spheres. Indicate by arrows the direction of the electric field lines. [2] (c) A conducting wire attached to a negatively charged metal object is connected to earth. This allows 2.0 × 1010 electrons, each carrying a charge of 1.6 × 10–19 C, to flow to earth in 1.0 × 10–3 s. Calculate (i)
the total charge that flows,
charge ..................................... (ii)
the average current in the wire.
current ..................................... [3]
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10 82. Fig. 8.1 shows a transformer and a rectifier used in a battery charging circuit for a 12 V battery. T1 240 V a.c.
T2
primary
secondary Fig. 8.1
(a) The transformer produces an output of 15 V across the secondary coil. Calculate a suitable turns ratio for the transformer.
turns ratio = ................................ [2] (b) Fig. 8.2 shows the 15 V output across the secondary coil. potential difference
time
Fig. 8.2 On the same axes, sketch the graph of the potential difference across the terminals T1 and T2 before the battery is connected. [2] (c) Explain how the circuit converts an a.c. supply into a d.c. output. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (d) On Fig. 8.1, draw in a battery connected so that it may be charged.
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[1]
For Examiner’s Use
11 (e) When fully charged, the 12V battery can supply a current of 2.0 A for 30 hours (1.08 × 105 s).
For Examiner’s Use
Calculate (i)
the battery power when supplying a current of 2.0 A,
power = ...................................... (ii)
the total energy that the battery will supply during the 30 hours.
energy = ...................................... [4]
9
Fig. 9.1 shows three resistors connected across a low voltage d.c. supply, and a c.r.o. A
B
C
d.c. supply
F
D
E
Y input Fig. 9.1
3. (a) Explain how you would use a 1 V d.c. supply to calibrate the c.r.o. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (b) On Fig. 9.1, draw in the connections between the c.r.o. and the circuit so that the potential difference between points C and D may be measured. [2] (c) The potential differences between A and F, B and C, C and D, and D and E are measured. State the relationship between them. .......................................................................................................................................... ......................................................................................................................................[2]
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9 84. Fig. 8.1 shows a battery with a resistor connected across its terminals. The e.m.f. of the battery is 6.0 V.
For Examiner’s Use
6.0 V
Fig. 8.1 The battery causes 90 C of charge to flow through the circuit in 45 s. (a) Calculate (i)
the current in the circuit,
current = .................................. (ii)
the resistance of the circuit,
resistance = ..................................
(iii)
the electrical energy transformed in the circuit in 45 s.
energy = .................................. [6] (b) Explain what is meant by the term e.m.f. of the battery. .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[2]
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10 95. A transformer has an output of 24 V when supplying a current of 2.0 A. The current in the primary coil is 0.40 A and the transformer is 100% efficient. (a) Calculate (i)
the power output of the transformer,
power = .................................. (ii) the voltage applied across the primary coil.
voltage = .................................. [4] (b) Explain (i)
what is meant by the statement that the transformer is 100% efficient, ................................................................................................................................... ................................................................................................................................... ...................................................................................................................................
(ii)
how the transformer changes an input voltage into a different output voltage. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... [4]
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For Examiner’s Use
11 106. Fig. 10.1 and Fig. 10.2 show two views of a vertical wire carrying a current up through a horizontal card. Points P and Q are marked on the card.
P
Q
For Examiner’s Use
vertical wire
view from above the card Fig. 10.1
Fig. 10.2
(a) On Fig. 10.2, (i)
draw a complete magnetic field line (line of force) through P and indicate its direction with an arrow,
(ii)
draw an arrow through Q to indicate the direction in which a compass placed at Q would point. [3]
(b) State the effect on the direction in which compass Q points of (i)
increasing the current in the wire, ...................................................................................................................................
(ii)
reversing the direction of the current in the wire. ................................................................................................................................... [2]
(c) Fig. 10.3 shows the view from above of another vertical wire carrying a current up through a horizontal card. A cm grid is marked on the card. Point W is 1 cm vertically above the top surface of the card.
T R
vertical wire carrying current
S W
Fig. 10.3 State the magnetic field strength at S, T and W in terms of the magnetic field strength at R. Use one of the alternatives, weaker, same strength or stronger for each answer. at S ........................................................................ at T ........................................................................ at W........................................................................ 0625/3/M/J/03
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[3] [Turn over
10 87. Fig. 8.1 shows a 240 V a.c. mains circuit to which a number of appliances are connected and switched on.
240 V a.c.
refrigerator
fan 1.2 kW
200 W
60 W
60 W
Fig. 8.1 (a) Calculate the power supplied to the circuit. power = …………..[1] (b) The appliances are connected in parallel. (i)
Explain what connected in parallel means. ................................................................................................................................... ...................................................................................................................................
(ii) State two advantages of connecting the appliances in parallel rather than in series. advantage 1 ............................................................................................................... advantage 2 ............................................................................................................... [3] (c) Calculate (i)
the current in the refrigerator, current = …………..
(ii) the energy used by the fan in 3 hours, energy = ………….. (iii) the resistance of the filament of one lamp. resistance = ………….. [7] © UCLES 2004
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For Examiner’s Use
11 9 8. Electromagnetic induction can be demonstrated using a solenoid, a magnet, a sensitive ammeter and connecting wire.
For Examiner’s Use
(a) In the space below, draw a labelled diagram of the apparatus set up to demonstrate electromagnetic induction. [2]
(b) State one way of using the apparatus to produce an induced current. .......................................................................................................................................... ......................................................................................................................................[1] (c) Explain why your method produces an induced current. .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[2] (d) Without changing the apparatus, state what must be done to produce (i)
an induced current in the opposite direction to the original current, ................................................................................................................................... ...................................................................................................................................
(ii)
a larger induced current. ................................................................................................................................... ................................................................................................................................... [2]
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12 109. (a) Fig. 10.1 shows the faces of two ammeters. One has an analogue display and the other a digital display. 3
2
A
4
A 5
0
1
Fig. 10.1 State what is meant by the terms analogue and digital. .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[2] (b) (i)
Name the components from which logic gates are made. ...............................................................................................................................[1]
(ii)
(iii)
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In the space below, draw the symbol for an AND gate. Label the inputs and the output.
[1]
Describe the action of an AND gate with two inputs.
[2]
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For Examiner’s Use
11 810. A student has a power supply, a resistor, a voltmeter, an ammeter and a variable resistor. (a) The student obtains five sets of readings from which he determines an average value for the resistance of the resistor. In the space below, draw a labelled diagram of a circuit that he could use.
[3] (b) Describe how the circuit should be used to obtain the five sets of readings. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (c) Fig. 8.1 shows another circuit. 6.0 V
A
resistor 3.0 Ω
resistor of unknown value
Fig. 8.1 When the circuit is switched on, the ammeter reads 0.50 A. (i)
Calculate the value of the unknown resistor. resistance = ………………. [2]
(ii)
Calculate the charge passing through the 3.0 Ω resistor in 120 s.
charge = ………………. [1] (iii)
Calculate the power dissipated in the 3.0 Ω resistor. power = ………………. [2]
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For Examiner’s Use
12 911. (a) Fig. 9.1 shows an a.c. supply connected to a resistor and a diode.
a.c. supply
resistor
For Examiner’s Use
output
Fig. 9.1 (i)
State the effect of fitting the diode in the circuit. ................................................................................................................................... .............................................................................................................................. [1]
(ii) On Fig. 9.2, sketch graphs to show the variation of the a.c. supply voltage and the output voltage with time. a.c. supply voltage 0
output voltage
time
0
time
Fig. 9.2 [2] (b) (i)
In the space below, draw the symbol for a NOT gate.
[1] (ii)
State the action of a NOT gate. ................................................................................................................................... ................................................................................................................................... .............................................................................................................................. [2]
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14
12. Fig. 11.1 shows a flexible wire hanging between two magnetic poles. The flexible wire is 11 connected to a 12 V d.c. supply that is switched off. wire fixed here
N
S
+ 12 V d.c. –
flexible wire hanging between magnetic poles wire fixed here Fig. 11.1 (a) Explain why the wire moves when the supply is switched on. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (b) State the direction of the deflection of the wire. .......................................................................................................................................... ..................................................................................................................................... [2] (c) When the wire first moves, energy is changed from one form to another. State these two forms of energy. from ........................................................... to ............................................................ [1]
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For Examiner’s Use
15 (d) Fig. 11.2 shows the flexible wire made into a rigid rectangular coil and mounted on an axle. magnetic pole axle
N
N coil
magnetic pole
S
S
axle
Fig. 11.2 (i)
Add to the diagram an arrangement that will allow current to be fed into the coil whilst allowing the coil to turn continuously. Label the parts you have added. [1]
(ii)
Briefly explain how your arrangement works. ................................................................................................................................... .............................................................................................................................. [2]
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For Examiner’s Use
9 813. Fig. 8.1 shows an electrical circuit.
For Examiner’s Use
12.0 V d.c.
A one metre resistance wire
C
R
B
4.0 Ω sliding contact Fig. 8.1
The resistance of the lamp is 4.0 Λ when it is at its normal brightness. (a) The lamp is rated at 6.0 V, 9.0 W. Calculate the current in the lamp when it is at its normal brightness. current = ........................[2] (b) The sliding contact C is moved to A. The lamp lights at its normal brightness. Calculate (i)
the total circuit resistance, resistance = ........................[1]
(ii)
the potential difference across the 4.0 Λ resistor R. potential difference = ........................[1]
(c) The sliding contact C is moved from A to B. (i)
Describe any change that occurs in the brightness of the lamp. ..............................................................................................................................[1]
(ii)
Explain your answer to (i). .................................................................................................................................. ..............................................................................................................................[2]
(d) The 1 m wire between A and B, as shown in Fig. 8.1, has a resistance of 2.0 Λ. Calculate the resistance between A and B when (i)
the 1 m length is replaced by a 2 m length of the same wire, resistance = ........................[1]
(ii)
the 1 m length is replaced by a 1 m length of a wire of the same material but of only half the cross-sectional area. resistance = ........................[1]
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10 914. A transformer is needed to step down a 240 V a.c. supply to a 12 V a.c. output. (a) In the space below, draw a labelled diagram of a suitable transformer.
[3]
(b) Explain (i)
why the transformer only works on a.c., .................................................................................................................................. ..............................................................................................................................[1]
(ii)
how the input voltage is changed to an output voltage. .................................................................................................................................. .................................................................................................................................. ..............................................................................................................................[2]
(c) The output current is 1.5 A. Calculate (i)
the power output, power = ........................[1]
(ii)
the energy output in 30 s. energy = ........................[1]
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For Examiner’s Use
11 10 15. (a) Fig. 10.1 shows a positively charged plastic rod, a metal plate resting on an insulator, and a lead connected to earth.
positively charged plastic rod
metal plate insulator
lead connected to earth Fig. 10.1
Describe how the metal plate may be charged by induction. .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3] (b) An electrostatic generator sets up a current of 20 mA in a circuit. Calculate (i)
the charge flowing through the circuit in 15 s,
charge = ............................ (ii)
the potential difference across a 10 kΛ resistor in the circuit.
potential difference = ............................ [3]
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For Examiner’s Use
Topic 5: Atomic Physics
1
Background Radiation • Whenever radioactivity from a sample is measured, background radioactivity interferes with the readings.
• Background radioactivity is from rocks, soil and outer space.
• In one particular region, it remains reasonably constant.
• Background radioactivity is measured before an
experiment and then subtracted from all readings with the sample in place.
2
α-Particle Emission •
The nucleus is unstable and needs to eject mass.
•
An α-particle is emitted containing 4 AMU.
•
Overall p/n ratio not seriously affected.
α-particle
3 215
β -Particle Emission •
Nucleus unstable. A neutron needs to change into a proton.
•
An electron is produced in the process.
•
Electron emitted and becomes β-particle.
β-particle
4
γ-Radiation •
Nucleus excited and too much energy.
•
γ -ray emitted.
γ-ray
5
Properties of Radioactivity •
Nature
•
Effect of of magnetic and electric fields.
•
Penetration
•
Ionisation
•
Dangerous
•
Speed
6 216
Detecting Radioactivity •
Radioactivity is detected using a GM tube. This detects the ionisation in a low pressure tube. It is often connected to a counter.
•
Photographic film also detects radioactivity.
7
Summary of Radioactivity structure
charge
mass
penetration
range
detection
α β ᵧ 8
Sub-Atomic Particles • There are three subatomic particles. Particle
Charge
Mass
Proton
+1
1 AMU
Neutron
Neutral
1 AMU
Electron
-1
Negligible
9 217
Rutherford Scattering •
Large + α-particles are fired at gold atoms.
•
Most of the particles pass straight through the gold.
•
Some particles are deflected.
•
Some particles actually ‘bounce’ back towards the source.
10
Rutherford’s Nuclear Model Paths of α-particles
Gold Nucleus
•
Rutherford explained these results using the nuclear model of the atom. This says:
•
Most of the atom is empty space.
•
There is a positively charged nucleus.
•
Electrons orbit the nucleus in circular paths.
11
Nuclear Notation A
Z
X
•
Proton number (or Atomic Number) (Z) is the number of protons in the Nucleus.
•
Nucleon Number (or Mass Number) (A) is the total number of particles in the nucleus (protons + neutrons)
12 218
Isotopes •
Isotopes are two nuclei with the same number of electrons, the same numbers of protons, but different numbers of neutrons.
•
They are chemically identical, but physically different (density, radioactivity).
13
Half-Life •
Over time, the number of particles in a radioactive sample decreases, and so does the activity of the sample.
•
This produces an exponential decay curve.
•
The time taken for the number of radioactive nuclei to half is called the ‘half-life’.
•
It is also the time taken for the activity of THE SAMPLE to half.
14
Number of Particles
Decay Curve 1000000 750000 500000 250000 0 0
25
50
75
100
Time A similar shaped curve is produced for the activity of the sample against time with the same half-life.
15 219
Nuclear Reactions •
A nuclear reaction is a ‘random’ process.
•
It is impossible to predict exactly WHEN one will happen, but since there are so many nuclei in a sample, we can make good statistical estimates.
•
We can accurately predict the PROBABILITY of a reaction taking place in a certain time.
16
Nuclear Equations •
Nuclear reactions are shown with an equation.
•
The two key rules are:
•
The conservation of Proton Numbers (Charge).
•
The conservation of Nucleon Numbers (Mass).
•
A β-particle has a Nucleon number of 0 and a Proton number of -1.
17
Examples of Nuclear Equations 14 7
N + 24α → 178 O + 11 H U→
238 92
1 0 131 53
Th + 24α
234 90
n → 11 p + −10 β
0 I → 131 54 Xe + −1 β
18 220
Nuclear and Atomic Physics Quantity and symbol Proton, p Electron, e Neutron, n Nucleon Nuclide notation Proton Number, Z Nucleon Number, A Alpha Particle, α
Beta Particle, β Gamma Ray, γ Background Radiation
Radioactive Decay Alpha Decay Beta Decay Gamma Decay Half Life
Isotopes
Word equation / definition Positive particle found in the nucleus of an atom. Negative particle found in orbits around the nucleus of an atom. Neutral particle found in the nucleus Any particle found in the nucleus of an atom. A ZX Where X is the symbol for the nuclide The number of protons in the nucleus The number of nucleons in the nucleus A helium nucleus, consisting of 2 protons and 2 neutrons, given out when a nucleus decays A high speed electron, given off when a neutron in the nucleus decays in to a proton and beta particle. The proton remains in the nucleus. Electromagnetic radiation, sometimes given off when a nucleus decays. There is a small amount of radiation around us all the time because of radioactive materials in the environment. It is mainly from sources such as soil, rock, air, building materials, food and drink, and even space. Radioactive decay is a random, spontaneous event that cannot be change by chemical or physical methods. A A-4 4 ZX → Z-2Y + 2 α A A 0 ZX → Z+1Y + -1β A A 0 ZX → ZX + 0γ The half life of a radioactive source is the time taken for half the available particle to decay. It is constant for a source. The atoms of one element are not all exactly alike. Some may have more neutrons than others. These different versions of the element are called isotopes. They have identical chemical properties, although the atoms have different masses. Isotopes have the same proton number, but different neutron numbers
221
Symbol equation 1 0
charge
1p
+1
-1e
-1
1
0n
4
α
+2
-1β
-1
2
0
0
0γ
0
0
iGCSE Physics Past Paper Questions Paper 1 Compilation Atomic & Nuclear Physics
222
17
1. The diagram shows a radioactivity experiment. 39 counter LDR
absorber –
What is the effect on the light-dependent resistor (LDR) when it gets dark? resistance of LDR source p.d. across LDR radiation detector A decreases decreases When a piece of paper is usedincreases as the absorber, the count rate drops to the background count B decreases rate. C increases decreases 2. What radiation is the source emitting? D increases increases A
alpha only
B beta only 37 An alternating potential difference (p.d.) is applied to the Y-plates of a cathode-ray oscilloscope. CThegamma onlyis turned off. time-base D alpha, beta and gamma Which of the following patterns would appear on the screen? 40 3.
22 10 Ne
represents anAatom of neon.
B
C
How many neutrons does it have? A
10
B
12
C
22
D
32
4. What is a beta-particle? 38 A
a helium nucleus
B
a high-energy electron
C
four protons
D
two neutrons
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D
17
5. The diagram shows a radioactivity experiment. 39 counter
absorber
source
radiation detector
When a piece of paper is used as the absorber, the count rate drops to the background count rate.
6. What radiation is the source emitting?
7. 40
A
alpha only
B
beta only
C
gamma only
D
alpha, beta and gamma
22 10 Ne
represents an atom of neon.
How many neutrons does it have? A
10
B
12
C
22
D
32
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When the temperature of the water is increased, the reading on the ammeter increases. 18 What is component X? 8. An atom of lithium contains three protons and three electrons. 40 A a capacitor The nucleon number (mass number) of the atom is 7. B a light-dependent resistor How C many a reedneutrons relay are there in the atom? AD
3a thermistor B 4
C
7
D
10
9. Which type of radiation can be stopped by a sheet of paper? 38 A
α-particles
B
β-particles
C
γ-rays
D
X-rays
10. The half-life of a radioactive substance is 5 hours. A sample is tested and found to contain 0.48 g 39 of the substance. How much of the substance was present in the sample 20 hours before the sample was tested? A
0.03 g
B
0.12 g
C
1.92 g
D
7.68 g
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18
11. Which line correctly describes -particles? 38 electric charge
penetrates 1 cm of aluminium?
A
negative
yes
B
negative
no
C
positive
yes
D
positive
no
39 12. A small amount of a radioactive isotope contains 72 billion unstable nuclei. The half-life of the isotope is 4 hours. How many unstable nuclei would remain after 12 hours? A
6 billion
B
9 billion
C
18 billion
D
24 billion
13. How many nucleons are in a nucleus of 40 A
19
U C L E S 2004
B
20
39 19 K
C
? 39
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D
58
17
14. Which type of radiation has the gre atest ionising effect? 38 A
-particles
B
-particles
C
-rays all have the same ionising effect
D
15. A powder contains 400 mg of a radioactive material that emits -particles. 39 The half-life of the material is 5 days. What mass of that material remains after 10 days? 0 mg
A
B
40 mg
C
100 mg
D
200 mg
16. In the symbol below, A is the nucleon number and Z is the proton number. 40 A Z
X
What is represented by the symbol? A
an electron
B
a neutron
C
a nuclide
D
an X-ray 16
17. The nucleus of a neutral atom of lithium is represented by 73 Li. 40 How many protons, electrons and neutrons does the atom contain? protons
electrons
neutrons
A
7
7
3
B
3
7
3
C
3
4
4
D
3
3
4
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15
18. The diagram shows five atoms in a radioactive substance. The atoms each give out an α-particle. 38 1st particle atom 1 atom 2
atom 5
atom 4
atom 3
2nd particle
19. Atom 1 is the first to give out a particle. Atom 3 is the second to give out a particle. Which atom will give out the next particle? A
atom 2
B
atom 4
C
atom 5
D
impossible to tell
39 20. A Geiger counter detects radiation from radioactive sources. A radioactive source is inside a thick aluminium container as shown.
radioactive source
2m Geiger counter
thick aluminium container Which type of radiation from this source is being detected? A
α-particles
B
β-particles
C
γ-rays
D
radio waves
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iGCSE Physics Past Paper Questions Paper 3 Compilation Atomic & Nuclear Physics
229
12 10 Some liquid from an atomic power station is known to be radioactive. A sample of this liquid is tested in a laboratory. (a) In the space below, draw a labelled diagram of the test apparatus used to verify that α-particles are emitted from the liquid. [2]
(b) Explain how the apparatus may be used to estimate the quantity of α-radiation being emitted from the sample. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (c) State any two safety precautions that the technician might take whilst making the test. precaution 1 ..................................................................................................................... .......................................................................................................................................... precaution 2 ..................................................................................................................... ..................................................................................................................................... [2]
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For Examiner’s Use
12
For Examiner’s Use
11 (a) A radioactive isotope emits only α-particles. (i)
In the space below, draw a labelled diagram of the apparatus you would use to prove that no β-particles or γ-radiation are emitted from the isotope.
(ii)
Describe the test you would carry out. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ...................................................................................................................................
(iii)
Explain how your results would show that only α-particles are emitted. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... [6]
(b) Fig. 11.1 shows a stream of α-particles about to enter the space between the poles of a very strong magnet.
N α-particles
S
Fig. 11.1 Describe the path of the α-particles in the space between the magnetic poles. .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3] 0625/3/M/J/03
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For Examiner’s Use
13 11 (a) α-particles can be scattered by thin gold foils. Fig. 11.1 shows part of the paths of three α-particles. Complete the paths of the three α-particles.
[3]
α-particle 1 α-particle 2
α-particle 3
gold nuclei
Fig. 11.1 (b) What does the scattering of α-particles show about atomic structure? .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[2] (c) State the nucleon number (mass number) of an α-particle. nucleon number = …………………[1]
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13 10 (a) Fig. 10.1 is the decay curve for a radioactive isotope that emits only β-particles.
For Examiner’s Use
400 count rate counts / min
300 200 100 0
0
10
20
30 time / min
40
Fig. 10.1 Use the graph to find the value of the half-life of the isotope. Indicate, on the graph, how you arrived at your value.
half-life …………………………. [2] (b) A student determines the percentage of β-particles absorbed by a thick aluminium sheet. He uses a source that is emitting only β-particles and that has a long half-life. (i)
In the space below, draw a labelled diagram of the apparatus required, set up to make the determination.
[2] (ii)
List the readings that the student needs to take. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... .............................................................................................................................. [3]
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12 11 Fig. 11.1 shows a beam of radiation that contains !-particles, "-particles and #-rays. The beam enters a very strong magnetic field shown in symbol form by N and S poles.
For Examiner’s Use
N beam of radiation S
Fig. 11.1 Complete the table below. radiation
direction of deflection, if any
charge carried by radiation, if any
!-particles "-particles #-rays [6]
Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.
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PHYSICS 0625 IGCSE 2007
CURRICULUM CONTENT Students can follow either the Core curriculum only or they may follow the Extended curriculum, which includes both the Core and the Supplement. Students aiming for grades A* to C must follow the Extended curriculum. Students are expected to have adequate mathematical skills to cope with the curriculum. Reference should also be made to the summary list of symbols, units and definitions of quantities. Throughout the course, attention should be paid to showing the relevance of concepts to the students' everyday life and to the natural and man-made world. In order to encourage such an approach and to allow flexibility in teaching programmes to meet the more generalised Aims, the specified content of the syllabus has been limited. In this wider sense, as well as in the literal sense, the following material should be regarded as an examination syllabus rather than a teaching syllabus.
TOPIC
CORE
SUPPLEMENT
All students should be able to:
In addition to what is required for the Core, students following the Extended curriculum should be able to:
-use and describe the use of rules and measuring cylinders to determine a length or a volume -use and describe the use of clocks and devices for measuring an interval of time
-use and describe the use of a mechanical method for the measurement of a small distance -measure and describe how to measure a short interval of time (including the period of a pendulum)
-define speed and calculate speed from total distance total time
-distinguish between speed and velocity -recognise linear motion for which the acceleration is constant and calculate the acceleration -recognise motion for which the acceleration is not constant
1. General Physics 1.1 Length and time
1.2 Speed, velocity acceleration
and
-plot and interpret a speed/time graph or a distance/time graph -recognise from the shape of a speed/time graph when a body is (a) at rest, (b) moving with constant speed, (c) moving with changing speed -calculate the area under a speed/time graph to determine the distance travelled for motion with constant acceleration -demonstrate some understanding that acceleration is related to changing speed -state that the acceleration of free fall for a body near to the Earth is constant
-describe qualitatively the motion of bodies falling in a uniform gravitational field with and without air resistance (including reference to terminal velocity)
1.3 Mass and weight
-show familiarity with the idea of the mass of a body -state that weight is a force -demonstrate understanding that weights (and hence masses) may be compared using a balance
-demonstrate an understanding that mass is a property which 'resists' change in motion -describe, and use the concept of, weight as the effect of a gravitational field on a mass
1.4 Density
-describe an experiment to determine the density of a liquid and of a regularly shaped solid and make the necessary calculation
-describe the determination of the density of an irregularly shaped solid by the method of displacement and make the necessary calculation
5235
PHYSICS 0625 IGCSE 2007
TOPIC
CORE
SUPPLEMENT
1.5 Forces (a) Effects of forces
-state that a force may produce a change in size and shape of a body -plot extension/load graphs and describe the associated experimental procedure
-describe the ways in which a force may change the motion of a body -find the resultant of two or more forces acting along the same line
(b) Turning effect
-describe the moment of a force as a measure of its turning effect and give everyday examples -describe, qualitatively, the balancing of a beam about a pivot
(c) Conditions for equilibrium
-state that, when there is no resultant force and no resultant turning effect, a system is in equilibrium
(d) Centre of mass
-perform and describe an determine the position of mass of a plane lamina -describe qualitatively the position of the centre of stability of simple objects
-recall and use the relation between force, mass and acceleration (including the direction) -describe, qualitatively, motion in a curved path due to a perpendicular force (F = mv2 / r is not required)
-perform and describe an experiment (involving vertical forces) to verify that there is no net moment on a body in equilibrium -apply the idea of opposing moments to simple systems in equilibrium
experiment to the centre of effect of the mass on the
(e) Scalars and vectors
1.6 Energy, work and power (a) Energy
-interpret extension/load graphs -state Hooke’s Law and recall and use the expression F = k x -recognise the significance of the term 'limit of proportionality' for an extension/load graph
-demonstrate an understanding of the difference between scalars and vectors and give common examples -add vectors by graphical representation to determine a resultant -determine graphically a resultant of two vectors -demonstrate an understanding that an object may have energy due to its motion or its position, and that energy may be transferred and stored -give examples of energy in different forms, including kinetic, gravitational, chemical, strain, nuclear, internal, electrical, light and sound -give examples of the conversion of energy from one form to another and of its transfer from on place to another -apply the principle of energy conservation to simple examples
6236
-recall and use the expressions 2 k.e.= ½ mv and p.e. = mgh
PHYSICS 0625 IGCSE 2007
TOPIC
CORE
SUPPLEMENT
(b) Energy resources
-describe how electricity or other useful forms of energy may be obtained from (i) chemical energy stored in fuel (ii) water, including the energy stored in waves, in tides, and in water behind hydroelectric dams (iii) geothermal resources (iv) nuclear fission (v) heat and light from the Sun
-show an understanding that energy is released by nuclear fusion in the Sun -show a qualitative understanding of efficiency
(c) Work
-relate, without calculation, work done to the magnitude of a force and the distance moved
-describe energy changes in terms of work done -recall and use ∆W = Fd = ∆E
(d) Power
-relate, without calculation, power to work done and time taken, using appropriate examples
-recall and use the equation P = E/t in simple systems
-relate, without calculation, pressure to force and area, using appropriate examples
-recall and use the equation p = F/A
1.7 Pressure
-describe the simple mercury barometer and its use in measuring atmospheric pressure -relate, without calculation, the pressure beneath a liquid surface to depth and to density, using appropriate examples
-recall and use the equation p = hρg
-use and describe the use of a manometer 2. Thermal Physics 2.1 Simple kinetic molecular model of matter (a) States of matter
-state the distinguishing solids, liquids and gases
properties
(b) Molecular model
-describe qualitatively the molecular structure of solids, liquids and gases -interpret the temperature of a gas in terms of the motion of its molecules -describe qualitatively the pressure of a gas in terms of the motion of its molecules -describe qualitatively the effect of a change of temperature on the pressure of a gas at constant volume -show an understanding of the random motion of particles in a suspension as evidence for the kinetic molecular model of matter -describe this motion (sometimes known as Brownian motion) in terms of random molecular bombardment
-relate the properties of solids, liquids and gases to the forces and distances between molecules and to the motion of the molecules
(c) Evaporation
-describe evaporation in terms of the escape of more-energetic molecules from the surface of a liquid -relate evaporation and the consequent cooling
-demonstrate an understanding of how temperature, surface area and draught over a surface influence evaporation
(d) Pressure changes
-relate the change in volume of a gas to change in pressure applied to the gas at constant temperature
-recall and use the equation pV = constant at constant temperature
7237
of
-show an appreciation that massive particles may be moved by light, fastmoving molecules
PHYSICS 0625 IGCSE 2007
TOPIC 2.2
CORE
SUPPLEMENT
(a) Thermal expansion of solids, liquids and gases
-describe qualitatively the thermal expansion of solids, liquids and gases -identify and explain some of the everyday applications and consequences of thermal expansion -describe qualitatively the effect of a change of temperature on the volume of a gas at constant pressure
-show an appreciation of the relative order of magnitude of the expansion of solids, liquids and gases
(b) Measurement of temperature
-appreciate how a physical property which varies with temperature may be used for the measurement of temperature and state examples of such properties -recognise the need for and identify fixed points -describe the structure and action of liquidin-glass thermometers
-demonstrate understanding of sensitivity, range and linearity
Thermal properties
(c) Thermal capacity
(d) Melting and boiling
-relate a rise in temperature of a body to an increase in internal energy -show an understanding of the term thermal capacity -describe melting and boiling in terms of energy input without a change in temperature -state the meaning of melting point and boiling point -describe condensation and solidification
-describe the structure of a thermocouple and show understanding of its use for measuring high temperatures and those which vary rapidly
-describe an experiment to measure the specific heat capacity of a substance -distinguish between boiling and evaporation
-use the terms latent heat of vaporisation and latent heat of fusion and give a molecular interpretation of latent heat -describe an experiment to measure specific latent heats for steam and for ice 2.3
Transfer of thermal energy (a) Conduction
-describe experiments to demonstrate the properties of good and bad conductors of heat
(b) Convection
-relate convection in fluids to density changes and describe experiments to illustrate convection
(c) Radiation
-identify infra-red radiation as part of the electromagnetic spectrum
(d) Consequences of energy transfer
-identify and explain some of the everyday applications and consequences of conduction, convection and radiation
-give a simple molecular account of heat transfer in solids
-describe experiments to show the properties of good and bad emitters and good and bad absorbers of infra-red radiation
3. Properties of waves, including light and sound 3.1
General wave properties
-describe what is meant by wave motion as illustrated by vibration in ropes, springs and by experiments using water waves -use the term wavefront -give the meaning of speed, frequency, wavelength and amplitude
8238
-recall and use the equation v = f λ
PHYSICS 0625 IGCSE 2007
TOPIC
3.2
SUPPLEMENT
-distinguish between transverse and longitudinal waves and give suitable examples -describe the use of water waves to show (i) reflection at a plane surface (ii) refraction due to a change of speed (iii) diffraction produced by wide and narrow gaps
-interpret reflection, refraction diffraction using wave theory
and
Light (a) Reflection of light
(b) Refraction of light
(c) Thin converging lens
3.3
CORE
-describe the formation, and give the characteristics, of an optical image by a plane mirror -use the law angle of incidence = angle of reflection -describe an experimental demonstration of the refraction of light -use the terminology for the angle of incidence i and angle of refraction r and describe the passage of light through parallel-sided transparent material -give the meaning of critical angle -describe internal and total internal reflection -describe the action of a thin converging lens on a beam of light -use the term principal focus and focal length -draw ray diagrams to illustrate the formation of a real image by a single lens
(d) Dispersion of light
-give a qualitative account of the dispersion of light as illustrated by the action on light of a glass prism
(e) Electromagnetic spectrum
-describe the main features of the electromagnetic spectrum and state that all e.m. waves travel with the same high speed in vacuo
Sound
-describe the production of sound by vibrating sources -describe the longitudinal nature of sound waves -state the approximate range of audible frequencies -show an understanding that a medium is required in order to transmit sound waves -describe an experiment to determine the speed of sound in air -relate the loudness and pitch of sound waves to amplitude and frequency -describe how the reflection of sound may produce an echo
4. Electricity and magnetism 4.1 Simple phenomena of -state the properties of magnets magnetism -give an account of induced magnetism -distinguish between ferrous and nonferrous materials -describe methods of magnetisation and of demagnetisation
9239
-perform simple constructions, measurements and calculations
-recall and use the definition of refractive index n in terms of speed -recall and use the equation sin i /sin r = n -describe the action of optical fibres
-draw ray diagrams to illustrate the formation of a virtual image by a single lens -use and describe the use of a single lens as a magnifying glass
-state the approximate value of the speed of electro-magnetic waves -use the term monochromatic
-describe compression and rarefaction
-state the order of magnitude of the speed of sound in air, liquids and solids
PHYSICS 0625 IGCSE 2007
TOPIC
CORE
SUPPLEMENT
-describe an experiment to identify the pattern of field lines round a bar magnet -distinguish between the magnetic properties of iron and steel -distinguish between the design and use of permanent magnets and electromagnets 4.2
Electrical quantities (a) Electric charge
-describe simple experiments to show the production and detection of electrostatic charges -state that there are positive and negative charges -state that unlike charges attract and that like charges repel -describe an electric field as a region in which an electric charge experiences a force -distinguish between electrical conductors and insulators and give typical examples
(b) Current
-state that current is related to the flow of charge -use and describe the use of an ammeter
(c) Electro-motive force
-state that the e.m.f. of a source of electrical energy is measured in volts
(d) Potential difference
-state that the potential difference across a circuit component is measured in volts -use and describe the use of a voltmeter
(e) Resistance
-state that resistance = p.d./ current and understand qualitatively how changes in p.d. or resistance affect current -recall and use the equation R = V/I -describe an experiment to determine resistance using a voltmeter and an ammeter -relate (without calculation) the resistance of a wire to its length and to its diameter
(f) Electrical energy 4.3
-state that charge is measured in coulombs
-state the direction of lines of force and describe simple field patterns -give an account of charging by induction -recall and use the simple electron model to distinguish between conductors and insulators -show understanding that a current is a rate of flow of charge and recall and use the equation l = Q/t -distinguish between the direction of flow of electrons and conventional current -show understanding that e.m.f. is defined in terms of energy supplied by a source in driving charge round a complete circuit
-recall and use quantitatively the proportionality between resistance and the length and the inverse proportionality between resistance and cross-sectional area of a wire -recall and use the equations P = I V and E=IVt
Electric circuits (a)
Circuit diagrams
(b)
Series and parallel circuits
-draw and interpret circuit diagrams containing sources, switches, resistors (fixed and variable), lamps, ammeters voltmeters, magnetising coils, transformers, bells, fuses and relays -understand that the current at every point in a series circuit is the same -give the combined resistance of two or more resistors in series -state that, for a parallel circuit, the current from the source is larger than the current in each branch -state that the combined resistance of two resistors in parallel is less than that of either resistor by itself
240 10
-draw and interpret circuit diagrams containing diodes and transistors
-recall and use the fact that the sum of the p.d.’s across the components in a series circuit is equal to the total p.d. across the supply -recall and use the fact that the current from the source is the sum of the currents in the separate branches of a parallel circuit -calculate the effective resistance of two resistors in parallel
PHYSICS 0625 IGCSE 2007
TOPIC
CORE
SUPPLEMENT
-state the advantages of connecting lamps in parallel in a lighting circuit (c) Action and use of circuit components
-describe the action of a variable potential divider (potentiometer) -describe the action of thermistors and light dependent resistors and show understanding of their use as input transducers -describe the action of a capacitor as an energy store and show understanding of its use in time delay circuits -describe the action of a relay and show understanding of its use in switching circuits -describe the action of a diode and show understanding of its use as a rectifier -describe the action of a transistor as an electrically operated switch and show understanding of its use in switching circuits -recognise and show understanding of circuits operating as light sensitive switches and temperature operated alarms (using a relay or a transistor)
(d) Digital electronics
4.4
Dangers of electricity
4.5
Electromagnetic effects
-explain and use the terms digital and analogue - state that logic gates are circuits containing transistors and other components -describe the action of NOT, AND, OR, NAND and NOR gates -design and understand simple digital circuits combining several logic gates -state and use the symbols for logic gates (the American ANSI#Y 32.14 symbols will be used) -state the hazards of (i) damaged insulation (ii) overheating of cables (iii) damp conditions -show an understanding of the use of fuses and/or circuit-breakers
(a) Electromagnetic induction
-describe an experiment which shows that a changing magnetic field can induce an e.m.f. in a circuit
(b) a.c. generator
-describe a rotating-coil generator and the use of slip rings -sketch a graph of voltage output against time for a simple a.c. generator -describe the construction of a basic ironcored transformer as used for voltage transformations -recall and use the equation (Vp / Vs) = (Np / Ns) -describe the use of the transformer in high-voltage transmission of electricity -give the advantages of high voltage transmission
(c) Transformer
241 11
-state the factors affecting the magnitude of an induced e.m.f. -show understanding that the direction of an induced e.m.f. opposes the change causing it
-describe the principle of operation of a transformer -recall and use the equation Vp lp = Vs Is (for 100% efficiency)
-discuss energy losses in cables
PHYSICS 0625 IGCSE 2007
TOPIC
CORE
SUPPLEMENT
(d) The magnetic effect - describe the pattern of the magnetic field of a current due to currents in straight wires and in solenoids
-state the qualitative variation of the strength of the magnetic field over salient parts of the pattern -describe the effect on the magnetic field of changing the magnitude and direction of the current
-describe applications of the magnetic effect of current, including the action of a relay (e) Force on a current- -describe an experiment to show that a carrying conductor force acts on a current-carrying conductor in a magnetic field, including the effect of reversing: (i) the current (ii) the direction of the field (f) d.c. motor -state that a current-carrying coil in a magnetic field experiences a turning effect and that the effect is increased by increasing the number of turns on the coil -relate this turning effect to the action of an electric motor
-describe an experiment to show the corresponding force on beams of charged particles -state and use the relative directions of force, field and current -describe the effect of increasing the current
4.6 Cathode ray oscilloscopes -describe the production and detection of (a) Cathode rays cathode rays -describe their deflection in electric fields -state that the particles emitted in thermionic emission are electrons (b) Simple treatment of cathode-ray oscilloscope
-describe in outline the basic structure and action of a cathode-ray oscilloscope (detailed circuits are not required) -use and describe the use of a cathode-ray oscilloscope to display waveforms
5. Atomic Physics 5.1
Radioactivity (a) Detection of radioactivity
-show awareness of the existence of background radiation -describe the detection of α-particles, βparticles and γ -rays
(b) Characteristics of the -state that radioactive emissions occur three kinds of randomly over space and time emission -state, for radioactive emissions: (i) their nature (ii) their relative ionising effects (iii) their relative penetrating abilities (c) Radioactive decay
-state the meaning of radioactive decay, using equations (involving words or symbols) to represent changes in the composition of the nucleus when particles are emitted
(d) Half-life
-use the term half-life in simple calculations which might involve information in tables or decay curves
(e) Safety precautions
-describe how radioactive materials are handled, used and stored in a safe way
242 12
-describe their deflection in electric fields and magnetic fields -interpret their relative ionising effects
PHYSICS 0625 IGCSE 2007
TOPIC 5.2
CORE
SUPPLEMENT
(a) Atomic model
-describe the structure of an atom in terms of a nucleus and electrons
-describe how the scattering of α-particles by thin metal foils provides evidence for the nuclear atom
(b) Nucleus
-describe the composition of the nucleus in terms of protons and neutrons -use the term proton number Z -use the term nucleon number A -use the term nuclide and use the nuclide
The nuclear atom
A
notation Z X (c) Isotopes
-use the term isotope -give and explain examples of practical applications of isotopes
243 13
