PG Brainstormer - 4C
PG Brain Stor m er - 4 C MAGNETIC EFFECTS OF CURRENT & ELECTROMAGNETIC INDUCTION
An Ultimate Tool to understand advanced High School Physics
Tim e A llo w e d
ARORA Sir by ASHISH ARORA
60 M in
M a x im u m M a rk s
72
SECTION - I : (Comprehension Type) Type)
In this section 8 Paragraphs are ar e given each with with 2 to 4 questions. Each question has h as four choices (A), (A), (B), (C) and (D) out of which ONLY ONE is correct. Marking Scheme - +3 for RIGHT answer and -1 for WRONG answer. answer.
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Y X A L A G S C I S Y H P
Comprehension - 1 Paragraph for Question Nos. 1 to 3 Figure Figure show showss a conduc conducting ting rod of negli negligib gible le resis resistanc tancee that that can can slide slide on on smoot smooth h U-shape U-shaped d rail made of wire wire of of
resistance 1 /m. Position of the conducting rod at t = = 0 is shown. sh own. The time dependent magnetic field B =
t 2 Tesla 2
is switched on at t = = 0 sec. ( t is is in seconds)
m c 0 2
Conducting Rod
40cm
1.
The current in the loop at t = = 0 due to induced emf is : (A) 0.16 A, clockwise (B) 0.08 A, clockwise
(C) 0.08 A, anticlockwise
(D) zero
2.
At t = = 0, when the magnetic field is switched on, the conducting rod is moved to the left at constant speed 5 cm/s by some external means. The rod moves such that it remains perpendicular to the rails. At t = = 2s, induced emf has magnitude : (A) 0.1 V (B) 0.08 V (C) 0.04 V (D) 0.02 V
3.
Following situation of the previous question, the magnitude of the force required to move the conducting rod at constant speed 5 cm/s at the same instant t = = 2s, is equal to : (A) 0.16 N (B) 0.12 N (C) 0.08 N (D) 0.04 N
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Comprehension - 2 Paragraph for Question Nos. 4 to 6 Two Two uncharged identical capacitors A and B, each of capacitance C , and an inductor of inductance L are arranged as shown in the adjacent figure. At t = = 0, the switch S 1 is
closed while switch S 2 remains open. At time t = = t 0 = LC , switch S 2 is closed while 2 switch S 1 is opened. 4.
5.
S 1
(B) CE 2
(C) CE
L
S 2
(D) CE 4
The current flowing through the inductor ind uctor at t = = t 0 is : (A) 2CE
6.
E
The charge on capacitor A after time t 0 is : (A) 2CE
B
A
1 LC
(B) 0
(C)
1 CE × 2 LC
(D) CE ×
1 LC
After switch S 2 is closed and S 1 is opened, the maximum value of current through t he inductor is :
C (A) E L
(B)
C E 2 L
3 C E 2 L
(C)
5 C E 4 L
(D)
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PG Brainstormer - 4C
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7.
Comprehension - 3 Paragraph for Question Nos. 7 to 9 B A straight conductor AB of negligible resistance and mass m is placed on two parallel smooth r ails of negligible resistance as shown in the figure. Distance X k B between both the rails is l. Leftmost ends of both the rails is shorted with the help C l of a capacitor C . The conductor is joined to a non-conducting ideal spring of spring constant k which is fixed to a rigid support. The whole system is placed in A a static uniform magnetic field B which is directed into th e plane of the paper. Now the conductor is shifted to right by a distance x0 to compress the spring and the conductor is released from the position : (Effect of gravity can be neglected)
(A) 2 8.
m CB l 2 k
k
m 2
(B) x0
m CB l
2 2
2 2 (C) CB l k 2
k
m CB2l 2 k
(D) 2
k
(C) x0
m CB l
2 2
k m
(D) x0
k
CB 2l 2
Find the maximum charge on the capacitor : k
(A) x0 CBl
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(B)
Find the maximum speed of the conductor : (A) x0
9.
Y X A L A G S C I S Y H P
Find the least time to reach the conductor to its original position, where the spring was in its natural length :
m CB l
2 2
(B) x0 CBl
k
m CB l
2 2
(C) x0CBl
k m
(D) x0 CBl
Comprehension - 4 Paragraph for Question Nos. 10 to 12 Two capacitors of capacitance C and 3C are charged to potential difference V 0 and 2V 0 respectively and connected to an inductor of inductance L as shown in the figure. Initially
k CB 2l 2
V 0
–
+
13.
14.
S
L
3C L
(B) V 0 3C L
(C) 2V 0
3C L
(D) V 0 C L
V 0 4
(B)
3V 0 4
(C)
5V 0 4
(D) None of these
Potential difference across capacitor of capacitance 3C when the current in the circuit is maximum : (A)
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3C
Potential difference across capacitor of capacitance C when the current in the circuit is maximum : (A)
12.
–
The maximum current in the inductor is : V (A) 3 0 2
11.
+
C
the current in the inductor is zero. Now the switch S is closed. 10.
2V 0
V 0 4
(B)
3V 0 4
(C)
5V 0 4
(D) None of these
Comprehension - 5 Paragraph for Question Nos. 13 to 14 In an L – C circuit shown in the figure, C = 1F, L = 4H. At time t = 0, charge in the capacitor is 4C and it is decreasing at a rate of 5 C/s.
Maximum charge in th e capacitor can be (A) 10 C (B) 8 C
(C) 6 C
q +
–
C L
(D) 12 C
Charge in the capacitor will be maximum after time (in sec.) (A) 2 sin –1
2
(B) 2 cos –1
2
3 3 –1 –1 –1 (sin (2/3), cos (2/3), or tan (2/3) are in radian)
(C) 2 tan –1
2 3
(D) None of these
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PG Brainstormer - 4C
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Comprehension - 6 Paragraph for Question Nos. 15 to 17 The figure shown a rectangular loop ( ABCD) of wire of width L and one end in a uniform external magn etic field that is directed perpendicularly into the plane of the loop. This field is produced by a large electromagnet. Th e dashed lines show the assumed limits of the magnetic field. You are asked to pull this loop to the right at a constant velocity v . As you pull the loop you apply a constant force F to the loop because a magnetic force of equal magnitude but opposite direction acts on the loop to oppose you.
B ×
×
×
× ×
× ×
×
×
×
×
×
×
×
×
× ×
×
×
×
The direction of induced current in th e loop is (A) anticlockwise (B) clockwise
× ×
15.
×
×
× × ×
× ×
×
×
× ×
× × ×
F
× × ×
Y X A L A G S C I S Y H P
(C) No current is induced (D) Date insufficient
16.
The rate at which you do work, in terms of resistance (R) of loop, length L and magnetic field B , is (A)
17.
(B)
BL2 v R
(C)
BLv 2 R
(D)
B2 L2 v2 R
The rate at which th ermal energy appears in the loop as you pull it along at a constant speed is (A)
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BL2 v2 R
BL2 v2 R
(B)
B2 L2 v R
(C)
B2 Lv 2 R
(D)
B2 L2 v2 R
Comprehension - 7 Paragraph for Question Nos. 18 to 21 A physics lab is designed to study the transfer of electrical energy from one circuit to another by means of a magnetic field using simple transformers. Each transformer has two coils of wire electrically insulated from each other but wound around a common core of ferromagnetic material. The two wires are close together but do not touch each other.
The primary (1°) coil is connected to a source of alternating (AC) current. The secondary (2°) coil is connected to a resistor such as a light bulb. The AC source produces an oscillating voltage and current in the primary coil that produces an oscillating magnetic field in the core material. This in turn induces an oscillating voltage and AC current in the secondary coil. Students collected the following data comparin g the number of turns per coil (N) , the voltage (V) and the current (I) in the coils of three transformers.
Primary Coil
Secondary Coil
N1°
V1°
I 1°
N2°
V2°
I 2°
Transformer 1
100
10 V
10 A
200
20 V
5V
Transformer 2
100
10 V
10 A
50
5V
20 V
Transformer 3
200
10 V
10 A
100
5V
20 V
18.
The primary coil of a tran sformer has 100 turns and is connected to a 120 V AC source. How many turns are in the secondary coil if there’s a 2400 V across it? (A) 5 (B) 50 (C) 200 (D) 2000
19.
A transformer with 40 turns in its primary coil is connected to a 120 V AC source. If 20 W of power is supplied to the primary coil, how much power is developed in the secondary coil? (A) 10 W (B) 20 W (C) 80 W (D) 160 W Page 3
20.
PG Brainstormer - 4C Which of the following is a correct expression for R, th e resistance of the load connected to the secondary coil?
V1 N 2 (A) I1 I 1 21.
V1 N 2 (B) I 2 N 1
V1 N 1 (C) I1 N 2
V N (D) 1 1 I 2 N 2
2
A 12 V battery is used to supply 2.0 mA of current to the 300 turn s in the pr imary coil of a given transformer. What is the current in the secondary coil if N 2 = 150 turns? (A) zero (B) 1.0 mA (C) 2.0 mA (D) 4.0 mA Comprehension - 8 Paragraph for Question Nos. 22 to 24
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Y X A L A G S C I S Y H P
A particle (1) having positive charge q and mass m is moving along x-axis with a velocity v v0iˆ in space having
uniform and constant magnetic field B B0iˆ , where v0 and B0 are positive constants. At time t = 0 second, the
moving particle (1) strikes anoth er stationary uncharged particle (2) of mass m lying at origin, as shown in figure (i). The collision is perfectly elastic and the uncharged particle (2) after collision moves along a straigh t line (in x-y plane) making an angle 45° with positive x-axis, as shown in figure (ii). Assume that there is no transfer of charge between the particles during collision. B0
y
q, m
(2)
(1) v
m
(2)
45°
x
fig. (ii)
The time period of revolution of charged particle (after t = 0 second) is (A)
23.
m
x
fig. (i)
22.
B0
y
2 m qB
(B)
2 2 m qB
(C)
m
2q B
(D) None of these
The minimum time after t = 0, at which the charged particle touches x-axis is (A)
m
2q B
(B)
2 2 m qB
(C)
2 m qB
(D) After t = 0 charged particle does not touch x-axis. 24.
The minimum time after t = 0, at which velocity of both particles are parallel is
m (A) qB
(B)
m
2 m qB
(C)
2 2 qB
(D) Velocities of both cannot be parallel.
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PG Brainstormer - 4C
PG Brain Stor m er - 4 C MAGNETIC EFFECTS OF CURRENT & ELECTROMAGNETIC INDUCTION
An Ultimate Tool to understand advanced High School Physics
Time Allow ed
by ASHISH ARORA Sir
60 M in
M ax imum M arks
72
OMR Sheet for the PG Brainstormer - 4C
Y X A L A G S C I S Y H P A
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PG Brainstormer - 4C
PG Brain Stor m er - 4 C MAGNETIC EFFECTS OF CURRENT & ELECTROMAGNETIC INDUCTION
An Ultimate Tool to understand advanced High School Physics
Time Allow ed
by ASHISH ARORA Sir
60 M in
M ax imum M arks
72
A N S W ER K E Y
Y X A L A G S C I S Y H P SECTION - I : (Comprehension Type)
1. (D) 10. (A) 19. (B)
2. (A) 11. (C) 20. (B)
3. (D) 12. (C) 21. (A)
4. (C) 13. (C) 22. (A)
5. (D) 14. (D) 23. (C)
6. (C) 15. (B) 24. (A)
7. (D) 16. (D)
8. (A) 17. (D)
9. (A) 18. (D)
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