SERVICiO NACIONAL DE ADIESTR4MIENTQ EN TRABAJO INDUSTRIAL
MANUAL DE APRENDIZAJE
r
^
• INGLES TECNICO PARA
ELECTRICIDAD INDUSTRIAL v
y
CODIGO :89000058
Tecnico de Nivel Operativo
AUTORIZACI6N Y DIFUSION
MATERIAL DIDACTICO ESCRITO
FAMILIA OCUPACIONAL
ELECTROTECNI A
OCUPACION
ELECTRICISTA INDUSTRIAL TECNICO OPERATIVO
NIVEL
Con la finalidad de facilitar el aprendizaje en el desarrollo de la formacion y capacitacion en la ocupacion del ELECTRICISTA INDUSTRIAL a nivel naciona! y dejando la posibilidad de un mejoramiento y actualization permanente, se autoriza la APLICACION Y DIFUSION de material didactico escrito referido a INGLES TECNICO PARA ELECTRICISTA INDUSTRIAL. Los Directores Zonales y Jefes de Unidades Operativas son los responsables de su difusion y aplicacion oportuna.
DOCUMENTO APROBADO POR GERENTE TEGVICO DEL SENATI N° de Pagina ... 140.
Fecha:.
Registro de derecho de autor: 5101-2002
EL
SENAn TABLE OF CONTENTS ELECTRICITYSPECIALIZED ENGLISHCOURSE
UNIT ONE
Contents
HAND TOOLS, ELECTRICAL CONDUCTORS AND WIRING TECHNIQUES OBJECTIVES 01
UNIT TWO
LESSON A 1. HAND TOOLS CLASSWORK ASSIGMENT : LESSON A
02 13
LESSON B 1. ELECTRICAL CONDUCTORS AND WIRING TECHNIQUES CLASSWORK ASSIGMENT : LESSON B
16 24
ELECTRIC CURRENT AND MEASURING INSTRUMENTS OBJECTIVES 28 LESSON A 1. ELECTRIC CURRENT CLASSWORK ASSIGMENT : LESSON A
29 33
LESSON B 1. MEASURING INSTRUMENTS CLASSWORK ASSIGMENT : LESSON B
35 38
UNIT THREE CELLS AND BATTERIES OBJECTIVES
41
LESSON A 1. CELLS CLASSWORK ASSIGMENT : LESSON A
42 45
LESSON B 1. BATTERIES 47 50
CLASSWORK ASSIGMENT : LESSON B
UNIT FOUR
MAGNETISM
OBJECTIVES
52
LESSON A 1. MAGNETISM CLASSWORK ASSIGMENT : LESSON A
53 57
LESSON B 1. ELECTROMAGNETISM (Cont.) CLASSWORK ASSIGMENT : LESSON B
60 64
SENAT1
ELECTRICITY SPECIALIZED ENGLISH COURSE Contents
UNIT FIVE THE SIMPLE GENERATOR AND TYPES OF CURRENT
OBJECTIVES 67 LESSON A 1. THE SIMPLE GENERATOR 68 CLASSWORK ASSIGMENT : LESSON A 72 LESSON B 1. TYPES OF CURRENT 75 CLASSWORK ASSIGMENT : LESSON B 81
UNIT SIX SWITCHES AND RELAYS
OBJECTIVES 84 LESSON A 1. SWITCHES AND RELAYS 85 CLASSWORK ASSIGMENT : LESSON A 91
UNIT SEVEN FUSES AND CIRCUIT BREAKERS
OBJETIVES 95 LESSON A 1. FUSES AND CIRCUIT BREAKERS 96 CLASSWORK ASSIGMENT : LESSON A 102
UNIT EIGHT RESISTORS AND TRANSFORMERS
OBJECTIVES 105 LESSON A 1. RESISTORS 106 CLASSWORK ASSIGMENT : LESSON A 111 LESSON B 1. TRANSFORMERS 114 CLASSWORK ASSIGMENT : LESSON B 118
UNIT NINE POWER AND ELECTRICAL SAFETY
OBJECTIVES 121 LESSON A 1. POWER 122 CLASSWORK ASSIGMENT : LESSON A 125 LESSON B 1. ELECTRICAL SAFETY CLASSWORK ASSIGMENT : LESSON B
127 133
SEN^Tl
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 1 UNIT ONE
HAND TOOLS, ELECTRICAL CONDUCTORS AND WIRING TECHNIQUES
2.
OBJECTIVES Given a task the student will orally and/or in writing describe cable features. 1.
Given different pictures of hand tools the
student will orally and/or in writing identify
the following ones : ♦ standard screwdriver 4. Given figures of various conductors the
♦ chisel student will orally and/or in writing identify the
♦ Phillips screwdriver following features :
♦
file
ball-peen hammer •♦ rigid conduits
punch tool •♦ crimping
claw hammer •♦ flexible conduits
electric drillterminal / hand drill •♦ solder-type lug
open bundle end wrench •♦ cable
wood handsaw •♦ crimp-on terminal lug
box end wrench •♦ stranded conductor
pliers •♦ cable striper
♦
adjustable open'end wrench
♦
♦
straight hand snips
♦ soldering gun
soldering iron
3. 5.
♦ socket wrench hacksaw Given a task the student will orally and/or in writing describe cord features. Given a task the student will orally and/or in writing define the following terms :
♦
splice
♦
♦ friction tape ♦ male connector
• female connector ♦ soldering
d&.
Page 2
ELECTRICITY SPECIALIZED ENGLI8H COURSE
UNIT ONE
HAND TOOLS, ELECTRICAL CONDUCTORS AND WIRING TECHNIQUES
LESSON A 1. HAND TOOLS
In this lesson we will talk about some of the tools used by electricians. Look at figure 1. This figure shows a screwdriver. A screwdriver is used for tightening or loosening screws.
Figure 1Sc rew dri ver
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 3
Now look si the two types of screwdrivers in figure 2. Figure 2 A shows a standard screw driver. A standard screwdriver is used to tighten and loosen standard screws. Figure 2 B shows a Phillips screwdriver. A Phillips screwdriver is used to turn the PhHNps-head screws.
Look at figure 3. Screwdrivers are made in different sizes. So, remember when you use a screwdriver make sure you use the correct size. The screwdriver should fit property into the slot in the head of the screw. In this figure you can notice that the screwdriver in 2 A does not fit properly in the screw slot, while the tool in 2 B has fitted correctly.
ELECTRICITY SPECIALIZED ENGLISH C0UR8E
Page
4
Let’s talk about hammers. Hammers are used for pounding cr hitting. Look at the two types of hammers in figure 4. Figure 4 A shows a ball-peen hammer. A ball-peen hammer is used for hitting objects. Figure 4 B shows a claw hammer. A claw hammer is used for dri ving and pulling nails.
Now look at the next four figures. All of them show wrenches. You can see that wrenches have different sizes and shapes, but the purpose is the same. A wrench is used to tighten and loosen nuts and bolts.
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 5
Look at figure 5. Both ends of this wrench are open so it is called an open-end wrench
Look at figure 6. Both ends of this wrench are dosed so if is called a box-end wrench
.K '-y,\
----------------l !
rX J
;
1
1 ;
.... -
- -----------
Figure 6. Box-end wrench
Look at figure 7. This an adjustable open end wrench or crescent wrench because the size of the wrench can be adjusted
ELECTRICITY SPECIALIZED ENGLISH
COURSE
e
I
sfifa. Pag
6 Look at figure 8. This type of w rench comes in a set of different sizes. This wrench set is called a socket wrench . A socket wrench has a long handle that fits into the socket.
Let’s look another handy tool. Look at figure 9. This a picture of straight hand snips. Straight hand snips are used for cutting light sheet metal.
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 7
Let's look at a tool which is used to cut metal that is too heavy for snips. Look at figure 10. It is a hacksaw. A hacksaw is used to cut metal that is too heavy for snips to cut.
Look at figure 11. These are other tools for working metal. They are pictures of different kinds of chisels . Chisels are used for chipping and cutting metal.
ROUND NOSE CHISEL.
DIAMOND POINT CHISEL CAPE CHISEL
COLD CHISEL
Figure 11.- Chisels
1 ad&i
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 8
Look at figure 12. Another common tool is the fils. Again there are many kinds. The kind of file you use depends on the job to be done. Some are used for smoothing work, and others are used for sharpening tools.
CENTER PUNCH
33 ST AR TI NC PU NC H
PIN PUNCH
t ........... ""1) ALINING PUNCH
HOLLOW SHANK GASKET PUNCH
Now, look at figure 13. Here ere pictures of some commonly used punches. These are many kind of punches designed to do many kinds of work. The one you use depends on the job to be done. A punch is a tool which Is held In the hand and hit on one end with a hammer.
Figure
.- Punches
ELECTRICITY SPECIALIZED ENGLISH CQURBE
[
SENSJIPage 9 Let’s look at figure 14. Here are two kinds of drills. A hand d rill and an electric drill. Drills are used for making or drilling holes in metal or wood.
Then, let s see what is used to cut w ood. Look at figure 15. It shows a hand saw . A hand saw is used for cutting wood.
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 10
Now, let's take a look at some pliers. Look at figure 16. Pliers are made in many different sizes and shapes and are used for many different jobs.
Remember this about pliers. Pliers should never be used as a substitute
for a wrench. Let’s look at some of the uses for pliers. Pliers are used to hold objects and cut material such as safety wires, in figure 17. pliers are used to hold objects.
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 11
Look at figure 18. Plies are also used for cutting wire and nails. Look at figure 20. This is a tool that
Look at figure 19. In this pictures pliers are used for stripping the insulation of a wire.
is frequently used by electricians. It is a soldering Iron.
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 12
Now that you know what a soldering iron looks like, let’s see what is used for. Look at figure 21. This a picture of a solder. Solder is a metallic alloy that melts at a low temperature. Solder is used to join metal surfaces. The soldering iron is used to heat the metal surface to a temperature that will cause the solder lo melt and flow over the joint.
Look at figure 22. This is a soldering gun . It is used in places that are difficult to reach.
A
Page 13
ELECTRICITY SPECIALIZED ENGLISH COURSE
SENAn UNIT ONE
CLASSWORK ASSIGMENT : LESSON A
The following exercises should be completed in class with the instructor's assistance :
IFigure 1
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 14
1. Look at figure 1 on the last page. Fill in the blanks below. a.
indicates a _________________________________________
b.
indicates a _________________________________________
c.
indicates an __________ ____________________________
d.
indicates a __ _____________________________________ .
e.
indicates a ___________ _ ___________________________
f.
indicates a __________________________ __________ .
g.
indicates ____ ______________________ ______________
h.
indicates a _________________________________________
i. j.
indicates an __________ ___________ ________________ indicates a _____________________________________
2. What are hammers used for ?
3. What would you use to sharpen hand snips ?
4. What tools are used for chipping and cutting metal ?
5. A
is used for
for , it is used to ______________ wood.
6.
metal that is too Another cutting tool is the
are made in different can use them
nails and objects.
But
and shapes. We
for striDDina the
they
should not be for a wrench.
7. If you want turn a screw, what will you use ?
of a wire.
for
as
a
; or for
C3S
ELECTRICITY SPECIALIZED ENGLISH COURSE
8. Look et figure 2. Fill in the blanks below. a. indicates a _______________________ b. indicates a _______________________ c. indicates a ____________ __________
Page
15
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page
16
UNIT ONE
ELECTRICAL CONDUCTORS AND WIRING TECHNIQUES
LESSON B
1. CONDUCTORS in this unit we will talk about conductors and wiring techniques. During this lesson when we refer to conductors we mean the wire or combination of wires used for carrying an electric current. These conductors come in different sizes. The size and type of conductor you use depends on the job. In other words the job determines the size and type of conductor you use.
Let’s talk about wires, cords and cables. Look at figure 1. It shows three classifications of conductors. Figure 1 A shows a single solid wire or conductor. Figure 1 B shows a cable. A cable is a thick heavy wire. Figure 1 C shows a cord. A cord is a small insulated flexible conductor.
Cl—„ ■
CONDUCTOR 1 --- --------- ----------------
INSULATION
Figure 1. Conductors
------- -
SENJETI
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 17
Now look at figure 2. Figure 2 A shows a solid conductor. Then take a look at 2 B. It shows another type of conductor. It is made of a group of wires twisted together. This type of conductor is called stranded conductor
Look at figure 3. Certain circuits require a large number of conductors . This type of cable is used in circuits that require a large number of conductors. The conductors are insulated from each other.
ELECTRICITY SPECIALIZED ENGLI8H COURSE
Page 18
Look at figure 4. Here are three ways of installing conductors so they are neat and easy to handle. Look at figure 4 A. In 4 A the cables are tied in a bundle. A cable bundle consists of many conductors tied together. Look at figure 4 B. This shows conductors installed inside a rigid conduit. A rigid conduit is a tube usually made of aluminum alloy. Look at figure 4 C. Here the conductors are installed inside a flexible conduit. Figure 4 shows the three methods of installing conductors so they will be neat and easy to handle. The method you use will be determined by the job.
Now look at figure 5. Let s talk about a splice. A splice is made by twisting two wires together.
Figure 5- Splice
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 19
Look at figure 6. In this part of the lesson we will talk about the steps in making a splice. Look at figure 6 A. The first step is removing the insulation from the wire with a cable stripper. Now look at figure 6 B. The next step in making a splice is twisting the wires together. Then look at figure 6 C. The next step is soldering the splice. Solder and soldering Iron are used to solder the splice. In order to complete the splice, it must be insulated. Look at figure 6 D. Friction tape is wrapped around the splice. Friction tape is used to insulate the splice.
Figure 6 - Making a splice
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 20
Let’s see at two other devices used for making splices. Look at figures 7 and 8. Picture 7 shows a split-sleeve splicer. Here the conductor tips are inserted between the split- sleeve jaws. Then the slide rings are moved to the end of the sleeve. The slide rings close the sleeve jaws and this holds the conductors in the split-sleeve splicer.
Look at figure 8. It shows a crimp-on splicer. The crimp-on splicer is very simple. The stripped conductor tips are placed in the splicer. Then a crimping tool is used to squeeze or crimp the splicer so the conductor tips will remain in place.
SENAJ1
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 21
We talked about splicers, now let’s talk about terminal connections. Conductors are often connected to objects such as motors and switches. Since this is where the length of a conductor ends, these connections are called terminal connections. Look at figure 9. This is a conductor terminal connection. A conductor terminal connection is made by bending the
conductor around the terminal post Now. Look at figure 10. This connection is made with a solder-type terminal lug. in a soldertype terminal lug the conductor is soldered to the terminal lug.
SENSTI
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 22
Now look at figure 11. This shows a crimp-on terminal lug. The crimp-on terminal lug is squeezed or “crimped” onto a conductor.
Lets take a look at some other types of connectors that you will see. Look at figure 12. These are some of the connectors used for interconnecting cables and electronic circuits.
Now look at figure 13. There are two classifications of connectors : male and female. The
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 23
male connector has one or more contacts extending from the connector housing. The female connector is the one to which male connector is connected.
In this unit we talked about a few of the conductors, cables, splices, terminals and connectors used by electricians There are many more , but remember that the type you use depends on the job to be done.
A.
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 24 UNIT ONE
CLASSWORK ASS IG MEN T : LESSON B
The following exercises should be completed in class with the instructor’s assistance : 1. Look
at figure 1. Fill in the blanks below. a.
indicates a ________________________________________________ .
b.
indicates a. _____________________________________________________ .
c.
indicates a ______________________________________________________ .
2. In figure 1 are shown three
of
conductors, together, we
when many conductors are
The method
vou
call it cable will be
ELECTRICITY SPECIALIZED ENGLISH COURSE
4. The conductors come in _______________ determines the _________________ and conductor.
3.
Look at figure 2. Fill in the blanks below.
They are three __________ ______________ of a.
indicates a ___________________________
b.
indicates the _________________________
c.
indicates the _________________________
d.
indicates a ___________________________
e.
indicates a ________________________
sizes. The ________________ _____ of the appropriate
5. What is a cable ? 6. What do you call a small insulated flexible conductor ?
Page 25
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 26
7. What are the steps in making a splice ?
8. What is a splice ?
9. In order to insulate a splice a ___________
is used. It is
_________________________ around the 10. Look at figure 3. Fill in the blanks below.
a. indicates a _______________________ b. indicates a _______________________
11. Figure 3 shows two ____________________ ____________________________ splicer
for making _ ______________ . In a
Inserted between the ___________________ conductors are held in place by the ________
the conductor ______________ are ________________________ . The
________________ rings close the _______
______________ jaws when the
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 27
SENAT1
12. Look at figure 4. Fill in the blanks below. A. indicates a
_____________________
B. indicates a _______________________ C. indicates a _____________________ 13. In figure 4 are shown _________________ types of ________________________ connections. In a _______________ terminal _______________ the conductor is soldered to the ___________________ . The ______________________ terminal ____________ is made by _________________________ the conductor around the terminal _________________ .
14. Look at figure 5. Write the correct names in the blanks. a. is a _________________________________________ b. is a ________________________________________
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 28
UNIT TWO
ELECTRIC CURRENT AND MEASURING INSTRUMENTS
OBJECTIVES
1. Given a task the student will orally and/or in writing explain the meaning of the following terms : ♦
Current
♦
Electromotive force or voltage
♦
Resistance
♦
Conductor
♦
Insulator
♦
ampere
♦
volt
♦
ohm
2. Given figures of various electrical measuring instruments the student will orally and/or in writing identify and explain the purpose of each one of he following instruments : ♦
ammeter
♦
voltmeter
♦
multimeter ohmmeter
Page 29
ELECTRICITY SPECIALIZED ENGLISH C0UR8E
UNIT TWO ELECTRIC CURRENT AND MEASURING INSTRUMENTS
LESSON A :
1. ELECTRIC CURRENT
In this lesson we will deal with electric current. Look at figure 1. The charged objects have unlike charges.
Now, look at figure 2. Here a wire connects the two charged objects.
Look at figure 3. Let’s see what happens when connect a wire in this way. The wire permits electrons to move through it* The electrons move through
the
wire
from
negatively
charged object to the positively charged object. This movement of electrons through the wire is called electric current .
ELECTRICITY SPECIALIZED ENGLI8H COURSE
Page 30
A material that electrons can move through it is called a conductor. Copper permits electrons to move through it, so we can call it conductor. The names of some metals that permit electrons to move through them easily are :
♦
silver
♦ aluminum
♦
gold
♦ copper
Now, look at figure 4. Here is a picture of a piece of copper wire. Electrons or electric current is moving through the wire.
Look a! figure 5. Here again is picture of a copper wire. But there is also rubber around the copper wire.. The rubber will not permit electrons to move through it. Material that won t permit electrons to move through it is an Insulator. Another example of an insulator is glass, it will not permit electrons to move through it.
Electric current will flow through a conductor, but not through an insulator. Electric current will not flow through rubber.
We
have
talked
ELECTRICITY SPECIALIZED ENGLISH COURSE Figure
about
current,
6
Page
31
conductors and insulators. Now, look at figure 6. Here again we have current flowing through a wire. There is a force that pushes the current through the wire. This force that pushes the current through the wire is called electromotive force. Another name for electromotive force is Look at Figure 7. Remember the voltage pushes the current through the conductor. When current flows through a conductor it meets resistance. Resistance is opposing force. Resistance tries to keep current from flowing through a conductor.
At this time, we have learned what insulators and conductors are. We have also learned about voltage, resistance and current. Now let’s talk about the units of measurement for voltage, resistance and current.
Look at figure 8 A. it is a picture of water flowing through a pipe. The unit of measurement for water is the gallon. We can measure how many gallons of water flow through the pipe each minute. Now look at figure 8 B. It is a picture of current flowing through a conductor. We can measure the amount of current flowing through the wire. Now. just as the unit of measurement for water is the gallon, the unit of measurement for current is the ampere .
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 32
Now look at figure 9. In this picture voltage pushes the current through the conductor. The unit of measurement for voltage Is the volt. You can notice that resistance tries to keep electric current from flowing through a wire. The amount of resistance in a conductor can be measured. The unit of measurement for resistance is the ohm .
Figure 9
ELECTRICITY SPECIALIZED ENGLI8H COURSE
Page 33
UNIT TWO
CLASSWORK ASIGMENT : LESSON A
The following exercises should be completed in class with the instructor’s assistance : 1. What is the movement of electrons through a wire ?
2. What do we call a material that permits electrons to move through it ?
3. Is electric current the movement of protons or electrons through a wire ?
4. What do we call material that will not permit electrons to move through it ?
5. What is electric current ?
6. Will rubber permit electrons to move through it ?
7. Does electromotive force push or pull the current through a conductor ?
8. Aluminum is a aood
. It permits through it.
Other
tc are silver,
and
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 34
9. Will electric current flow through a conductor or an insulator ?
10. What is voltage ?
11. What is the rubber around a conductor called ?
12. What is the force or pressure that pushes the electrons through a conductor ?
13. ___________________ pushes the ____________________________ through a conductor, it is also called_________________________________________. Its units of measurement are the _________________ .
14. What tries to keep current from moving through a conductor ?
15. What is the movement of electrons through a conductor ?
16. What is resistance ?
for
17. The units of measurement are as follows : • is the
for
♦ * for
is the is the
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 35 UNIT TWO
ELECTRIC CURRENT AND ELECTRICAL MEASURING INSTRUMENTS
LESSON B
1. ELECTRICAL MEASURING INSTRUMENTS
In the last two lessons we studied current, resistance and voltage. We learned the units of measurement for current, resistance and voltage; these units are the ampere, the ohm and the volt. In this lesson we will talk about some electrical measuring instruments. Look at figure 1. These are pictures of measuring instruments. These measuring instruments are called meters. There are many types of meters,
you can find analog or digital meters. Now look at figure 2. They are a conductor and a meter. This conductor has current flowing through it. As you remember the ampere is the unit of measurement for current, ihe abbreviation for ampere is amp. The meter in figure 2 is used to measure current in amps. So this meter is an ammeter .
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 36
Look at figure 3. Here you see another type of meter. Remember, voltage pushes current through a conductor and the unit of measurement for voltage is the volt. The meter in figure 3 is used to measure voltage in volts. This meter is a voltmeter .
Look ai figure 4. This is again a picture of a meter. Now, answer this question ; What opposes current in a conductor? The answer is resistance, which is measured in ohms. The meter in figure 4 is an ohm m eter. The ohmmeter is used to measure resistance. Look at figure 5. This is a picture of another type of electrical measuring instrument. It is a muiiimeter. Multi is a prefix that means many. A multimeter has more than one' function.
It
has
three
elemental
functions, it measures either current, resistance
or
voltage.
Sometimes
multimeters can measure frequency or temperature too.
ELECTRICITY SPECIALIZED ENGLISH COURSE
SENAn
Page 37
Now, look at figure 6. The numbers on the face of the meter are called the scale. The meter also has a pointer or needle, that points to a number on the scale. In figure 6 it is pointing to 30 on the meter scale.
The pointer is movable. It moves across the scale. When the meter is not being used, the pointer is on zero. Look at figure 7 A. this meter is not in use. Now. look at figure 7 B, the meter is now measuring current. It shows 4 amps of current
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 38
UNIT TWO
CLASSWORK ASSIGMENT : LESSON B
The following exercises should be completed in class with the instructor’s assistance :
1. Look at figure 1 Fill in the blanks below : a. indicates a _______________________ b. indicates a _______________________ c. indicates an _ ____________________ d. indicates a _______________________
2. What do we call the measuring instruments in figure 1 ? 3. What instrument is used to measure electrical current ?
ELEC TRICITY SPECIALIZED ENGLISH COURSE
Page 39
SENAT1
4. What is the unit of measurement for current ?
5. What instrument is used to measure electromotive force ?
6. What is the unit of measurement for resistance ?
7. If you want to measure voltage, which meter will you use ?
8. What instrument measures resistance ?
EMF is measured by a
. The
current is the
unit of measurement for
. The
electrical
in amps. and its unit of measurement is the
be measured with an
10. What does multi mean ?
11. What meter can measure more than one electrical parameter ?
12. What are meters ?
measures opposes : it can
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 40
13. Which instrument can be used to measure either voltage, current or resistance ?
14. What is the purpose of an ammeter ?
15. What are the numbers on the face of the meter called ?
16. Name three functions of a multimeter ?
17. When you measure current, voltage or resistance, what part of the meter moves to the correct number on the scale ?
18. what is the meter scale ?
19. What is the purpose of an ohmmeter ?
20. When the meter is not woiking, where is the pointer pointing ?
A
SENAT1
ELECTRICITY SPECIALIZED ENGLISH C0UR8E
Page 41 UNIT THREE
CELLS AND BATTERIES
OBJECTIVES
1. Given a task the student will orally and/or in writing state the purpose of an electric cell.
2. Given a scheme of an electric cell the student will orally and/or in writing identify the following cell features: #
Zinc plate
*
Carbon plate
•
Electrolyte
3. Given a task the student will be able to define the following terms : • Chemical energy • Oead cell •
plate
4. Given a task the student will orally and/or in writing describe the following: • Wet-cell battery *
Dry-cell battery
5. Given a task the student will be able to define the following terms : ♦ Secondary cells • Primary cells ♦ Positive terminal *
Negative terminal
♦
Paste
*
Poles
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 42
SENAT UNIT THREE
CELLS AND BATTERIES
LESSON A 1. CELLS
In this lesson we will talk about of some of the methods used by man to produce electricity. Look at figure 1. This is a picture of an electrical celt. A ceil is a small container. An electrical ceil is a small container that produces or makes electricity. Now. Let's study the different parts of an electric cell. Look at figure 2. They are pictures of two plates. A plate is a thin flat piece of material. There are two plates in this figure. Plate A is made of zinc. Zinc is a metal. Plate B is made of carbon Carbon is an element, but it is not a metal. Plate A is called zinc plate and plate B is called carbon plate .
71:10 Plate Figure 2
Figure 3
Carbon Plate
ELECTRICITY SPECIALIZED ENGLISH COURSE
SENAT
Page 43
A
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 44
SENAFI
We already know that an electrical cell contains a zinc plate, a carbon plate and the electrolyte. Now let’s see what chemical action takes place to produce electricity. Look at figuie 4. First, remember plate A is he zinc plate. Now the electrolyte will dissolve the zinc plate.
Let's make sure you understand what dissolve means. Look at Figure 5. When you put sugar into a glass of water it dissolves. A similar action occurs when the zinc plate is put into the electrolyte in an electric cell.
Now, let's see what happens when the electrolyte dissolves the zinc plate. Look at Figure 6. When the electrolyte dissolves the zinc plate, the zinc plate loses protons. Remember when an object loses protons it will have an excess of electrons, in figure 6. the zinc plate loses protons so it is negatively charged.
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 45
A SENAn Look at figure 7. Let's see what happens
4-
to the protons that are lost by the zinc plate. They combine with the electrolyte and move to the carbon plate by chemical action. When the protons reach the carbon plate, they meet electrons from the carbon plate The carbon plate loses
Figure 7
electrons therefore it will have a deficiency of electrons. So the carbon plate will be positively charged. Now, let's find out what happens when we connect a conductor to the positive carbon plate and the negative zinc plate. Look at figure 8. A conductor connects the negative zinc plate to the positive carbon plate. Now the electrons move through the conductor from the negative zinc plate to the positive carbon plate thus creating an electric l __ _ v ____ Figure 8
current. Electric cell produces an electric current by changing chemical energy into electrical energy .
Look at figure 9. In this picture the electrolyte has cornplelely dissolved the zinc plate. Now that the zinc plate has dissolved, the ceil can no longer produce electricity. An electric cell that can no longer produce electricity is called dead coll
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 46
UNIT THREE
CLASSWORK ASS1GMENT : LESSON A
The following exercises should be completed in class with the instructor’s assistance :
+
1. Look at figure 1 Fill in the balnks below a. indicates (tie _____________________ b. indicates the _____________________ c. indicates the __ ___________________ 2. What does an electric cell produce ?
3. What do we call the thin flat pieces of material ?
4. Look at figure I. How many plates do you see ?
5. Is carbon a metal ?
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 47
SENAT
6. What are the names of the two plates In the electric cell ?
7. What is the name of the liquid in an electric cell ?
8. In figure 1, the _______________ plate is positively ____________________ . The other plate is the ___________________ plate, it is _________________________ charged. The_______________________ dissolves the _________________ plate. It causes the _________ plate loses protons.
9. What dissolves the zinc plate ?
10. Where do the protons lost by the zinc plate go ?
11. What kind of charge will the zinc plate have when it loses protons ?
12. When the carbon plate loses electrons, will it have an excess or deficiency of electrons ?
13. Does the carbon plate have a positive or negative charge ?
14. How does an electric cell produce electricity ?
A
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 48
UNIT THREE
CELLS AND BATTERIES
LESSON B
I. BATTERIES
In (he last lesson, we studied a very simple electric cell Remember, an electric cell produces electricity by chemical action. It changes chemical energy into electrical energy. In this lesson we will study primary and secondary cells
Look at figure 1. There are two cells in this figure. The two cells are connected together. Two or more cells connected together make a battery .
Now. remember that the liquid in a battery is called an electrolyte. A battery that has a liquid electrolyte is a webceli battery
Look at figure 2 it is a wet-cell battery. This type of wet cell battery is a storage battery. A battery that stores electricity is a storage battery .
ELECTRICITY SPECIALIZED ENGLISH COURSE
SENATl SENAT1
Page
Now, look a! figure 3. This wet cell storage battery has 6 cells. When the cells lose their electrical charge they can be recharged. To recharge a cell means to again put an electrical charge in a cell. Cells that can be recharged after they have lost their charge are
Figure 3
called secondary cells. Secondary cells can be recharged. The storage battery in figure 3 has 6
secondary cells. These secondary cells can be recharged.
Look at figure 4. This is a picture of another type of cell. The electrolyte in this cell is not a liquid. It is a paste. Paste is not a liquid. Paste is a moist solid material. Look at figure 5, this is a figure of two different types of paste.
Now look again at figure 4. The electrolyte in this cell is paste. The paste is made of chemicals. A battery that uses paste as an electrolyte is a drycell battery. When this cell has lost its charge it can no longer be used and is thrown away, it can not be recharged. A cell that can not be recharged is a primary cell
49
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 49
Look at figure 6. Here we see a picture of a wet cell storage battery and a dry cell battery. The poles that you see on each
battery
are
called
battery
terminals. Both, the wet cell battery and the dry cell battery have two terminals each.
Look at figure 7. Every battery has two terminals. One is a positive terminal, the other is a negative terminal. The positive terminal has a positive charge and the negative terminal has a negative charge. In this picture the wires are connected to the positive and negative terminals. Wet cell storage batteries are used in cars, trucks, airplanes, etc. Look at figure 8. They are dry cell batteries. They are used in flash lights, radios, etc.
Page 50
ELECTRICITY SPECIALIZED ENGLISH COURSE
UNIT THREE
CLASSWORK ASSIGMENT : LESSON B
The following exercises should be completed in class with the instructor’s assistance. 1. Look at figure t . Fill in the blanks below. a. indicates a ___________________________________ b. indicates a ___________________________________
Figure 1 2. What do we call two or more cells connected together ?
3. In figure 1, how many cells does the wet cell battery have ?
4. What is the liquid in a battery called ?
5. An electric __________ produces ____________________ by __________________ action. Two or more ______________ connected together make a ___________________ . Battery that has a __________________ electrolyte is a __________________________ __________________ , It can be ______________________ when its cells lose their charge. Cells that can be ________________________ are called _________________
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 51
SENAT
6. How does a battery produce electricity ?
7. What do we call a battery that has a liquid electrolyte ?
8. What is the name of a cell that can be recharged ?
9. Dry cell battery has______________ as an electrolyte. Paste is a _____ __________ ______________ material. It is not a ___________________ and it is made of ______________ . This kind of cell can ____________ be ____________________ when it lost its ___________ _____ It is called a _____________________________
10. In dry cell batteries. Is the electrolyte a liquid or paste ?
1T. What is a primary cell ?
12. What type of battery uses a liquid electrolyte ?
13. What are the poles of the battery ?
14. What are the names of the two terminals of a battery ?
15. Does wet cell battery have primary or secondary cells ?
ELECTRICITY SPECIALIZED ENGLISH COURSE
UNIT FOUR Page 52
MAGNETISM
OBJECTIVES 0
1
.
Given a task the student will orally and/or in writ ing state the meaning of the following terms:
♦
0
magnet
♦ magnetic Field
natural magnet temporary magnet
• poles • magnetic flux
permanent magnet
♦
electromagnetism
2. Given a picture of different type of magnets the student will orally and/or in writing identify correctly the following features : •
straight bar magnet
• horseshoe magnet •
electromagnet
•
core
•
coil
•
loop
3. Given a task the student will explain how a magnetic is produced around a conductor.
4. Given the following terms the student will identify and use them to explain the electromagnetic phenomena. •
artificial
•
magnetic lines of force
•
deflect
•
reinforce
• residual magnetism
ELECTRICITY SPECIALIZED ENGLISH COURSE
SENAn
Page 53
UNIT FOUR
MAGNETISM
LESSON A
1. MAGNETS
In the last two lessons you studied the chemical
method
for
producing
electricity. In order to understand how generators produce electricity, we must understand magnets. During this lesson we will study magnets.
Look at figure 1. This is a picture of a magnet. A magnet is an object that attracts iron and s teel .
There are two types of magnets. They are natural magnels and artificial magnets. First let’s learn what natural magnets are. Look at figure 2. This object has been magnetized. When an object is magnetized it has been made into a magnet. In figure 2, the object has been magnetized by nature. Objects that have been magnetized by nature are natural magnets. They are already magnets when found by man.
ELECTRIC ITT SPECIALIZED ENGLISH C0UR8E
Page 54
Now, look at figure 3. This is a picture of an artificial magnet. Artificial magnets are made by man. Remember, natural magnets are magnetized by nature and artificial magnets are magnetized by man. Look at figure 4. These are two main types of artificial magnets. They are the permanent magnet and the temporary magnet. An object that will stay magnetized for a long time is a permanent magnet. The other magnet is a temporary magnet. An object that stays magnetized for a short time is a temporary magnet
A
permanent magnet
is
made of hard steel. It’s difficult to magnetize hard steel,
but
once
it
Permanent Magnet
is
magnetized it will keep its magnetism for a long time. The temporary magnet is
Temporary Magnet
made of soft iron. Soft iron
Figure 4
can be magnetized easily, but loses its magnetism very quickly
ELECTRIC ITT SPECIALIZED ENGLISH C0UR8E
Page 55
Look at figure 5 A. It is magnetic compass. The needle of a compass is a magnet. One end of the needle points north, the other end points south. The end of the compass needle that points to the north is called north-seeking pole or north pole. Northseeking means that the end of the needle is trying to find or is pointing toward the north. The end that points south is called the south-seeking pole or south pole. Look at figure 5 F3. The two ends of the magnet are the north and south poles.
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 55
Now, look at figure 6 A. There is force between the poles of a magnet. The north pole and the south pole of the two magnets will attract each other. Now, look at 6 B. Two north poles or two south poles will repel each other The basic law of magnetism says unlike poles attract each other and like poles repel each other.
Let’s Look at figure 7. There is a magnetic field see around the magnet. The area around a what magnet in which magnetism can be detected or found is called magnetic field. All magnets have a magnetic field.
agne c of Force makes a magnetic field. Look at figure 8. You can see the lines that come from the north pole and go to the south pole of the magnet. These lines are caiieu magnetic lines of force. The magnetic lines of force make the magnetic field. The total number of magnetic lines of force around a magnet is the magnetic flux . Figure 8
nes
7
ELECTRIC ITT SPECIALIZED ENGLI8H COURSE
Page
Look at figure 9. Magnets have different shapes. This magnet is straight and made of a bar of iron or steel. So this magnet is called a straight bar magnet
Look at figure 10. This magnet is called a horseshoe magnet because it is shaped like a horseshoe or letter “U”.
56
Page 57
ELECTRICITY SPECIALIZED ENGLISH COURSE
UNIT FOUR
CLASSWORK ASSIGMENT : LESSON A
The following exercises should be completed in class with the instructor’s assistance.
1. What is a magnet ?
2. What does magnet attract ?
3. What do we call a magnet that is magnetized by man ?
4. What do we call an object that attracts iron and steel ?
5. What is the name of the magnet that is magnetized by nature ?
6. We say that an object is ___________ ____________ , when it has been made into a ______________________ . Objects ____________________ by man are called maanets.There
magnets,
the
are two tvDes of maanets
maanets.
7 Which artificial magnet will keep its magnetism for a long time ?
8. Name two types of artificial magnets
and
the
SENAJ1
ELECTRICITY SPECIALIZED ENGLISH COURSE
9. Which magnet is made of soft iron ?
10. Is it easy or difficult to magnetize hard steel ?
11. How long will soft iron keep its magnetism ?
12. Which magnet is made of hard steel ?
13. What do we call the ends of a magnet ?
15. What is the area around the magnet where magnetism can be detected ? 14. What are the names of the two poles of a magnet ?
16. What is magnetic flux ?
17. What makes a magnetic field ?
18. Which is more difficult to magnetize, hard steel or soft iron ?
Page 58
ELEC TRIG ITT SPECIALIZED ENGLISH COURSE
19. Look at figure 1. Fill in the blanks below. a. indicates a _______________________ b. indicates a _____ . ________________
20. Do unlike poles of two magnets attract or repel each other?
21. Will two north poles attract or repel each other ?
22. Do all magnets have a magnetic field ?
Page 59
A
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 60
SENAIl
UNIT FOUR
MAGNETISM
LESSON B
1. ELECTROMAGNETISM
In the last lesson we talk about natural and artificial magnets. Now we will learn how a magnetic field is produced by electric current.
Look at figure 1. It is a picture of a conductor with current flowing through to it. The circles that you see around the conductor are magnetic lines of force. There is a magnetic field around the conductor. The current flowing through the conductor causes a magnetic field around the conductor. Magnetism produced by an electric current is called elecliomagnetism
A
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 61
Look at figure 2. Here is a picture of a conductor. There is no current flowing through it. Since no current is flowing, there is no magnetic field around the conductor.
Page 62
ELECTRICITY SPECIALIZED ENGLISH COURSE
A
B
Let's see how electric current produces a magnetic field around a conductor. Look at figure 3. Conductor A has a compass next to it. There is no current flowing through the conductor. The compass needle is pointing north. There is no magnetic field around conductor A, because there is no current flowing through it.
Now, look at conductor B. Conductor B has a current flowing through it, and the magnetic field deflects the compass needle. Deflects means to move or turn to the side. Since, the compass needle deflects we know there is a magnetic field around the conductor.
Now, let s see how a magnetic field can be stronger. Look a figure 4. This piece of wire has been bent into a circle. A piece of wire bent into a circle is a loop. When
an
electric
current
passes
through the loop , there will be a strong magnetic field in the center of the loop.
A
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 63
SENat figure 6. In this figure there are 4 loops Look Afl
Now, listen carefully. Many loops together make a coil.
Now. look at figure 7. There are two coils here. Coil A has three loops and coil B has five loops. Thus, the more loops a coils has, the stronger the magnetic field should be. So in figure 7 coil B should have the strongest magnetic field because it has more loops than coil A.
Remember the magnetic fields of each loop reinforce each other. The more loops a coils has, the stronger the magnetic field. If there is no current flowing through the coil, it won't have a magnetic field
Look at figure 8. In picture 8 A, there is coil and a piece of soft iron. Remember,
soft
iron
can
be
magnetized very easily, but soft iron also loses its magnetism very quickly. Now. look at figure 8 B, here the soft iron has been placed in the center of the coil. The coil now has a soft Iron core. Core means center part.
A
Page 64
ELEC TRICITY SPECIALIZED ENGLISH COURSE
SENATl
Look at figure 9. It is a coil with a soft Iron core. The soft iron core increases the strength of the magnetic field of a coil.
A soft iron core in a coil of wire produces a magnetic field when current flows through the electromagnet.
coil. An
This is an electromagnet
produces a magnetic field by using an electric current.
Look
at
figure
10
A.
It
is
an
electromagnet. Current is flowing through the electromagnet. The electromagnet attracts iron and steel. Now. look at figure 10 B. There is no current in the electromagnet. Since there is no current, there is no magnetic field , and iron and steel drop from the magnet. Remember, in an electromagnet, the electric current is the magnetizing force.
Now. Look at figure 11 The magnetizing force has been removed, but there is just a very small amount of magnetism left in the electromagnet. magnetism
This
that
small
remains
amount after
of the
magnetizing force has been removed is residual remaining.
magnetism.
Residual
means
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page
SENfin
UNIT FOUR
CLASSWORK ASSIGMENT : LESSON B
The following exercises should be completed in class with the instructor’s assistance.
1. What causes the magnetic field around a conductor ?
2. What kind of magnetism is produced by an electrical current ?
3. What is electromagnetism ? 4. Look at figure 1. • Is there a magnetic field around conductor A ?. Why?
In which direction is the compass needle pointing ?
64
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 65
5. Is electromagnetism produced by electric current or by a natural magnet ?
6. What does deflect mean ?
7. In figure 1, what does the magnetic field around conductorB do to the compass needle?
8. What is a loop ?
9. The __________________ produces a _________________ field in the area around the __________________ . When a piece of _______________ is bent into a circle it js called a _____________________ . Many ___________________ together make a ____________. The magnetic _____________ is strangest in the______________ of the ______________.
10. What do we call many loops together ?
11. What is a core ?
12. Will a soft iron core in a coil strengthen or weaken the magnetic field ?
13. How long does soft iron keep its magnetism ?
A
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 66
SENAJ1
14. Look at figure 2. Fill in the blanks below. a. indicates the _____ ________
_____
b. indicates the _____________________ c. indicates the _____________________
15. What is the magnetizing force in an electromagnet ? 16. What is another word for remaining ? 17. What is residual magnetism ? 18. In an
____________________ the electric ________________ is the magnetizing
___________________ . When current is removed from the coil ,
, __________
force also disappear but, a small _________________ of ___________________ left in the ____________ ____________ . This small ________________________ of that remains is called
ELECTRICITY SPECIALIZE
D ENGLISH COURSE
Page 67 UNIT FIVE
THE SIMPLE GENERATOR AND TYPES OF CURRENT OBJECTIVES
1. Given a picture of a simple generator the student will orally and/or in writing identify the following features : •
armature
•
stator
•
electromagnet
•
conductor
•
magnetic lines of force
2. Given a task the student will state the purpose of a generator.
3. Given a task, the student will orally and/or in writing define the following terms correctly :
• electromagnetic induction • •
circuit direct current (DC)
• alternating current (AC) • AC generator • DC generator •
frequency
4. Given pictures of a basic generator, the student will orally and/or in writing identify correctly the following features:
•
commutator
♦ stator
armature «
• brushes slip rings
ELECTRICITY SPECIALIZED ENGLISH COURSE
UNITPage FIVE 68
THE SIMPLE GENERATOR AND TYPES OF CURRENT LESSON A
1. THE SIMPLE GENERATOR
Just to make sure that you remember the last lesson let's make a review. Look at Figure 1. They are three types of magnets, a permanent magnet, a temporary magnet and an electromagnet. Remember, an electric current causes the magnetic Field around an electromagnet
in this lesson we will study how a magnetic
MAGNETIC FIELD
Field produces a voltage or EMF in a conductor. Look at Figure 2. It is a conductor. Current is flowing through the conductor. The current causes a magnetic
DIRECTION OF CURRENT
Field around the conductor.
Figure 2 Now, look at Figure 3. Here are two conductors. There is current flowing through conductor A. This causes a magnetic Filed around conductor A. Conductor B is placed in the magnetic field of conductor A.
ELECTRICITY SPECIALIZE
Remember, conductor “A" has a current
D ENGLISH COURSE
Page 69
A 1} l B CURRENT CURRENT Figure 3's'? -A Electromagnetic induction
Now. let’s see / how electromagnetic /
which causes a magnetic field. When
induction is used to produce electricity.
conductor B is moved into the magnetic
Look at figure 4. Here are two ends of a
field of conductor A, the magnetic field
magnet. They are called the north and
causes the electrons in conductor B to
south poles. There are magnetic lines of
move. The movement of electrons in a
force between the north and south poles
conductor, caused by moving the
of the magnet.
conductor through a magnetic field, is called electromagnetic induction Look at figure 5 There is a conductor, it is between the ends of the magnet. The conductor is in the magnetic field. When the conductor is moved through the magnetic field, the electrons in the conductor move. This movement of electrons in a conductor is called electric current as you already know.
Now, listen carefully. This is how a generator produces electricity. A generator is an electric machine that produces electricity. A generator produce electricity by changing mechanical energy to electrical energy.
ELECTRICITY SPECIALIZE
D ENGLISH COURSE
Page 70
Let’s learn the names of some of the parts of a generator. Look at figure 6. This is picture of a simple generator. The part that turns or rotates in the magnetic field is called the armature. Now, look at the ends of the magnet in figure 6. This magnet is part of the generator. It does not move, so it is called the stator .
Let's see how the armature is rotated in the magnetic field. Look at figure 7. It is a picture of a generator. The armature is turned mechanically. It is turned by mechanical energy. When the armature is turned, electrical energy is produced. So we say a generator produces electricity by changing mechanical energy into electrical energy.
Figure 7
ELECTRICITY SPECIALIZE
D ENGLISH COURSE
Page 71
Now, let’ see at different types of generators. Look at figure 8. This type of generator has an electromagnet which provides the magnetic field. Remember, electric current produces the
magnetic
field
around
an
electromagnet. Most generators use an electromagnet to produce the magnetic field . We know an electromagnet produces the magnetic field in most generators. Now. look at figure 9. This type of generator uses a permanent magnet to provide the magnetic field. A generator that uses a permanent magnet to provide the magnetic field is called a magneto .
The generator is a very important means of producing electricity. Let's review all the methods used for producing electricity we have studied. Three means for producing electricity are : • • •
friction cells and batteries generators
Remember, friction produces static electricity. Cells and batteries produce electricity by chemical action. The generator produces electricity by changing mechanical energy into electrical energy.
ELECTRICITY SPECIALIZE
D ENGLISH COURSE
Page 72
UNIT FIVE
CLASSWORK ASSIGMENT : LESSON A
The following exercises should be completed in class with the instructor’s assistance.
1. What causes the magnetic field around an electromagnet ?
2. What happens to the area around the conductor when current is flowing ?
Look at figure 1 and answer the following three questions. 3. What causes the magnetic field around conductor “A” ?
4. Is conductor “B” inside the magnetic field or outside the magnetic field of conductor “A”?
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 7
SENAT1
5. What causes the electrons to move in conductor “B" ?
6. What is electromagnetic induction ? 7. Look al figure 2. Fill in the blanks below. a. indicates the _____________________ b. indicates the _____________________
c. indicates the _____________________ d. indicates the ____________ 3. What are the two ends of the magnet called ?
9. What happens when the conductor moves through the magnetic field ?
by changing ________________
10. Generators produce
____ energy. The part that turns is
into
called
The part
that remains fixed is called
ASENAJ1
ELECTRICITY SPECIALIZED ENGLISH COURSE
11. What does electromagnetic induction cause in the armature ?
13. Which type of generator uses a permanent magnet to provide the magnetic field ? 12. How does a generator produce electricity ?
14. What type of magnets are used are used in generators ?
15. In a generator, what is the part that rotates ?
16. Which machine uses electromagnetic induction to produce electricity ?
17. What produces static electricity ? 19. What produces electricity by changing mechanical energy into electrical energy ? 18. What produces electricity by chemical action ?
20. What is a magneto ?
Page 74
A
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 75
5ENAT1
THE SIMPLE GENERATOR AND TYPES OF CURRENT
UNIT FIVE
LESSON B 1. TYPES OF CURRENT
In this lesson we will learn the different types of current Before you can study the types of current you must understand circuit. Look at figure 1 Here you can see a conductor connected to the positive and negative terminals of the battery. This conductor provides a path of current. The complete path of an electric current is called a circuit.
I
Now, that you know what a circuit is. let’s take a took at the type of current produced by cells and batteries. Look at figure 2 . it is a picture of a circuit. A conductor is connected to the battery terminals. The electrons can flow only from Hie negative terminal to the positive terminal. The cunent is flowing in only one direction. Current that flows in only one direction is called direct current. The abbreviation for direct cunent is D.C. Remember, batteries produce only direct current .
i
ELECTRICITY SPECIALIZE
D ENGLISH COURSE
Page 76
The other type of current is alternating current. The word “alternating” means changing direction, so current that changes its direction is alternating current. The abbreviation for alternating current is A.C
Figure 3
Let's see how a generator can produce alternating current . Look at figure 3. It is a picture of a generator. The armature is the part of the generator that rotates, the stator is the part that does not move. The two rings that you see at the end of the armature are called slip rings, they turn when the armature turns. There are two brushes which touch the slip rings, they are connected to a circuit. The brushes may de made of metal or carbon.
ELECTRICITY SPECIALIZE
D ENGLISH COURSE
Page 77
Look at figure 4. Now, you will see what happens when the armature rotates. Remember when the armature rotates, the magnetic field will cause current to flow. Current flows from the armature , through the slip rings, brushes and circuit.
Now, look at figure 5 . Let’s see how alternating current is produced. In picture 5 , there is no electron flow, because the armature is not turning. In figure 6, the armature is turning and the magnetic field causes electrons to flow. This electron flow is current. You can see that the current flows from brush X to brush Y.
ELECTRICITY SPECIALIZE
D ENGLISH COURSE
Page 78
Look at the circle in figure 6. This picture represents current flow. The current flow started at zero and has now increased to its highest or maximum point.
Look at figure 7. The armature is still turning. The current flow is from brush X to brush Y. Now, look at the circle in figure 7 The amount of current flow is decreasing. Look at figure 8. When the armature is in this position . there is no current flow. Now, also
Flow Zero
look to the circle 8, the current flow is zero.
ELECTRICITY SPECIALIZE
D ENGLISH COURSE
Page 79
SENATl
Look at figure 9. The armature has rotated to another position. In this case the current flow is from brush Y to brush X, the current has changed direction. Now, look at the circle 9. The current flow has now reached its maximum point in this direction.
Look at figure 10. The armature has made a complete turn. There is no current flow when the armature is in this position. Now, look at circle 10, the current flow is zero. This figure represents one cycle of alternating current. One complete turn of the armature produces one cycle of alternating current.
% SENAn
ELECTRICITY
SPECIALIZED
ENGLISH COURSE
Page 80
So, you already know that one turn of the armature produces one cycle of alternating current. The number of cycles that occur In one second is the frequency of an alternating current. Frequency means how often something happens. When a current is alternating at 10 cycles per second, then the frequency is ten cycles per second. The abbreviation for cycles per second is “cps”. An AC generator produces alternating current.
Now, look at figure 11. This generator produces direct current. A generator that produces direct current is called a DC generator. Remember the AC generator has two slip rings connected to the armature. The DC generator has only one ring connected to the armature. The ring is a commutator. The commutator is a ring that changes alternating current to direct current
Figure 11
ELECTRICITY SPECIALIZE
D ENGLISH COURSE
Page 81
UNIT FIVE CLASSWORK ASSIGMENT : LESSON B
The following exercises should be completed in class with the instructor’s assistance :
b.
1. Look at figure 1. Fill in the blanks below: a. Indicates the _____________________ b. Indicates the _____________________ c. Indicates the _______________ _____ d. Indicates the _____________________
2. What is a circuit ?
3. Whgt is current that flows in only one direction called ?
4. What does D.C. stand for ?
ELECTRICITY SPECIALIZED ENGLISH COURSE
SENAfl Page
82 5. In how many directions does D.C. flow ?
6. Batteries produce _______________ current. In figure 1 , the armature is ____________ , so the magnetic ___________causes _________________ to flow. The current _____________from brush ______to _________ Y.
7. The _______________ rings are connected to the _______________________ and ______________ when the ________________ turns. 8. What do the brushes touch ?
9. What is another word for changing direction ?
10. What does A.C. stand for ?
11. Does alternating current flow in only one direction ?
12. In an A.C. generator, what does one turn of the armature produce ?
13. In reference with a generator, what does frequency mean ?
14. What is the abbreviation for cycles per second ?
ELECTRICITY SPECIALIZE
D ENGLISH COURSE
Page 83
15. When a ________________ is alternating 60 ______________ per second, then the _______________ is ___________ cycles per __________________ .
16. Look at figure 2. FiH in the blanks below: It is a ___________________________ a. Indicates the _____________________ b. Indicates the _____________________ c. Indicates the _____________________ d. Indicates the _____________________ 17. What does the commutator do ?
18. Does the commutator change direct current to alternating current ?
19. If the armature turns 110 times in two seconds, what is the frequency of the current ?
20. Explain the difference between alternating current and direct current.
ELECTRICITY SPECIALIZE
Page 84
D ENGLISH COURSE
UNIT SIX
SWITCHES AND RELAYS
OBJECTIVES
1. Given a task, the student will state correctly the purpose of a switch and its types.
2. Given the abbreviations S.P.D.T., D.P.S.T. and D.P.D.T. the student will define what these abbreviations stand for.
3. Given a picture , the student will orally and/or in writing identify correctly the following electrical symbols : •
single pole, single throw
•
single pole, double throw
•
double pole, single throw
•
double pole, double throw
• pushbuttom switch •
rotary or selector switch
•
battery
4. Given a task, the student will be able to draw a diagram of a simple relay.
ELECTRICITY SPECIALIZE
Page 85
D ENGLISH COURSE
UNIT SIX
SWITCHES & RELAYS
LESSON A
1. SWITCHES A switch is a device used for making or changing connections in a circuit. There are many types of switches . Before we can talk about the different types of switches, we have to learn some of the parts of a switch. Look at figure 1. The circuit wires are connected to the switch terminals. Now look at the pole. The pole is the movable contact of the switch. The contact opens or closes the circuit. Current flows through the circuit when the pole or movable contact
is in the closed position. The switch in figure 1 has only one pole. It is called a single - pole switch, because it has only one pole or movable contact. The pole of this switch can complete only one circuit. So we say S.P.S.T.
Pole or Movable Contact
Wire
Position
Wire
Switch Terminals
Figure 1 - Single-pole, single throw switch it is a single - throw switch . Single throw means he pole can complete only one circuit.
The full description of this switch should be single - pole, single - throw switch. The abbreviation for single-pole, single-throw is S.P.S.T .
ELECTRICITY SPECIALIZED ENGLISH COURSE
A Page
86 SENAfl
Now, look at figure 2. This switch has one pole. This pole can complete two circuits. It can complete either circuit A or circuit B. So we call it a single pole, double throw. The abbreviation for single-pole, double throw is S.P.D.T .
Look at figure 3. This switch has two poles, each pole can complete only one circuit. It is called double-pole, single throw switch. The abbreviation for double-pole, singlethrow is D.P.S.T .
D.P.S.T.
Figure 3 - Double-pole, single-throw switch.
ELECTRICITY SPECIALIZE
D ENGLISH COURSE
Page 87
Look at figure 4. This switch has two poles, each pole can complete two circuits but only one at the time. It is a double-pole, double-throw switch. The abbreviation for doublepole, doublethrow is D.P.D.T .
Look at figure 5. To complete a circuit with this type of switch you must push the button. This is a pushbutton switch. A pushbutton switch has a button that must be pushed to complete the circuit.
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 88
Now, look at figure 6. This is another type of switch. This type of switch must be turned or rotated to complete a circuit. This is a rotary switch. A rotary switch is sometimes called a selector switch , because you choose or select the position of the switch.
Figure 6 - Rotary or selector switch.
Look at figure 7. These are symbols for the different types of switches that we have talked about. These symbols are used in electronic diagrams or schematics. •
Symbol A represents a single-pole, single throw switch.
♦
Symbol B represents a single-pole, double throw switch.
♦
Symbol C represents a double-pole, single throw switch. B
♦
Symbol D represents a double-pole, double- thrdW switch.
•
Symbol E represents a pushbutton switch.
•
Symbol F represents a rotary or selector switch.
S.P.S.T. —o
cr o — S.P.D.T.
D.P.S.T.
D —o
>> D.P.D.T. —
O Or O —
Pushbutton
r o°°°o
O o-
°
Switch (Rotary or
Figure 7 Selector)
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 89
Before we talk about another type of switch , let’s look at another important symbol. Look at figure 8 A. This symbol represents a cell. Look at 8 B. This symbol represents a battery. It is made by combining the symbols of cells.
—
Figure 8 A - One cell
Figure 8 B - Battery
2. RELAY Now, look at figure 9. There are two circuits. Circuit A has a single-pole, single-throw switch. This circuit also has an electromagnet. Current creates a magnetic field around an electromagnet. There is also a spring connected to the soft Iron bar. There is a light in circuit B too.
The switch in circuit A is closed, current flows through the electromagnet. The magnetic field of the electromagnet attracts the soft iron bar in circuit B. The soft iron bar touches the contact.
Current now flows through circuit B and the light burns.
SENAT1
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 90
Look at figure 10. The switch in circuit A is now open. Since no current is flowing through the electromagnet, there is no magnetic field to attract the soft iron bar of circuit B. The spring pulls the soft iron and circuit B is again open and no current flows. The soft iron bar in circuit B is an armature .
Pictures 9 and 10 show how a relay operates. A relay is an electromagnetic switch that uses an armature to open or close a circuit.
Figure 10
ELECTRICITY SPECIALIZE
D ENGLISH COURSE
Page 91
UNIT SIX
CLASSWORK ASSIGMENT : LESSON A
The followtng exercises should be completed In class with the instructor’s assistance:
1.
Look at figure 1. Fill in the blanks bellow
Figure 1 shows a _________________________ a.
indicates the _______________________ or
b.
indicates the _________________________
c.
indicates the _________________________
2.
What is the purpose of a switch ?
3.
In figure 1, Where are the circuit wires connected ?
ELECTRICITY SPECIALIZE
D ENGLISH COURSE
4.
What is a pole in reference with a switch ?
5.
What type of switch can complete only one circuit ?
6.
The abbreviation for single-pole, single-throw is
Page 92
This type of ,
can________ only one _ pole. 7.
Look at figure 2.
2a. Indicates a_____ 2b. indicates a ____ 2c indicates a _____ 2d indicates a _____
because H has
il
Page 93
ELECTRICITY SPECIALIZED ENGLISH COURSE
8.
How many poles does S.P.D.T. switch have ?
9.
Which type of switch has two poles and each pole can complete only one circuit ?
10. •
Write the meaning of the abbreviations below:
8.P.D.T.__________________________________
• D.PD.T. __________________________________ • 8.P.8.T. __________________________________ • DP.S.T. __________________________________ a.
b.
+
Figure 3
11.
Look at figure 3. Fill in the blanks.
a. _______________________________________ represents a . b. _______________________________________ represents a .
12.
Write the name of the electrical symbols in figure 4.
1 13.
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
Look at figure 5. Fill In the blanks below.
a.
indicates the ________________________
b.
indicates the ________________________
c.
indicates the ________________________
d.
Indicates the ________________________
e.
indicates the ______________________
or
14. What Is a relay ?
15. What happens when current flows through an electromagnet ?
Page 94
LSSL
ELECTRIC ITT SPECIAL (ZED ENGLISH COURSE
Page 95 UNIT 8EVEN
FUSES AND CIRCUIT BREAKERS
OBJECTIVES
1.
Given a task the student will orally and/or writing will state the purpose of a fuse and circuit breaker.
2.
Given pictures of different types of fuses the student will orally and/or In writing identify the following features:
• plug fuse • cartridge fuse •
clips
•
socket
3.
Given a task the student will orally and/or in writing define the following terms:
• blown fuse • excessive current • predetermined level •
preset
•
reset
•
4.
rating of a fuse
Given a picture of a circuit breaker the student will identify it correctly.
ELECTRIC ITT SPECIALIZED ENGLISH
CS
COURSE
Page
UNIT 8EVEN
96
FU8E8 AND CIRCUIT BREAKERS
LE88ON A
1. FUSES In the last lesson we talk 8bout switches and relays. Let's begin this lesson by talking about the heat produced In a circuit. Look at figure 1. it is a diagram of a series circuit. Remember, EMF or voltage is the force that
pushes
current
through
Figure 1 - Series circuit
a
conductor and resistance opposes current in a conductor. When current flows through a wire and meet resistance, heat is produced. If the amount of current is increased, the amount of heat also increases. Not all conductors or wires can carry the same amount of current. Different types of conductors carry different amounts of current. The amount of current a conductor can carry has been pre -determ Ined. By pre-determlned we mean the amount of current a conductor can carry has been previously calculated. Look at figure 2. It was calculated that the conductor In this circuit could carry 5 amps of current. The predetermined amount of current this circuit can carry is 5 amps.
Now, listen carefully. When the current exceeds or goes above the predetermined 5 amps, the circuit will have excessive current .
£Zn
ELECTRIC ITT SPEC IALOEEO ENGLISH COURSE
Page 97
Excessive current in a circuit can cause a lot of damage. Look at figure 3 A. The predetermined current for this circuit Is 5 amps. The current Increased to 7 amps. So there are 2 amps of excessive current flowing through the circuit. Now, look at 3 B. The excessive current caused the wire to get very hot. Thus the excessive current in the circuit caused the fire.
Figure 3
Let’s see what can protect a circuit against excessive current. Look at figure 4. This circuit has a fuse . The fUse protects the circuit against excessive current.
Figure 4 Now, we wifl see how a fuse works. Look at figure 5. It is a circuit with a fuse. Current flows through the fbse in the circuit. The wire in the ftise melts at a low temperature. Each ftjse has a rating. The rating is the largest amount of current a fuse can cany. In figure 5, the ftise can carry only 7 amps of current, so its rating Is 7 amperes. When the current exceeds the rating of the fuse (7 amps), the wir e in the fuse will melt and open the circuit.
nan
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
98
Look at figure 6. The fuse in this figure had a rating of 10 amps. The wire in the fuse is melted because the current exceeded the rating of the fuse. So the excessive current melted the wire and opened the circuit. The excessive current can not flow through the circuit. The fuse protected the circuit against excessive current.
Let’s deal with another useful term. Instead of saying, when the current exceeds the fuse the rating of the fUse the wire in it melts and breaks the circuit, you may say, when the current exceeds the rating of the fuse , the ftise will blow. When a circuit has no current flow because of the fuse has melted, we can say the circuit has a blown fuse .
Look at figure 7. There is no current flow because of the circuit has a blown ftise. The blown fuse must be replaced before current can flow.
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
Page
99
Now, look at figure 8 A. This is one type of fuse. This type of fuse is called cartridge fuse. The cartridge fuse fits into the clips on the fuse block, it is easy to replace the cartridge fuse. Then, look at figure 8 B. This type of fuse is called plug fuse. The plug ftise screws into a socket.
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
Page 100
2. CiRCUTT BREAKERS
Look at figure 9. It shows a circuit breaker. A circuit breaker automatically opens a circuit when current becomes excessive. Look at figure 10. This circuit breaker is preset at a pre-determined level of 30 amps. When
Circuit' Breaker
Figure 9.- Circuit breaker
current exceeds the pre-determIned level of 30 amps the circuit breaker will automatically open the circuit. Now, to make sure the circuit breaker opens the circuit at 30 amps, you must preset the circuit breaker. Hen you preset the circui t breaker you adjust or set It to open at 30 amps.
s&n
Page
101 ELECTRIC ITT SPECIALIZED ENGLISH COURSE
Look at figure 11. Circuit breaker A is preset at 20 amps. The circuit is closed. Notice the button on the circuit breaker.
Now, look at circuit breaker B. The current exceeded 20 amps. The circuit breaker opened the circuit. The button popped out.
Look at circuit breaker C . To reset or close the circuit you must push the button in. There many other types of circuit breaker but ail of them have the same operation principle.
Button
Figure 11 Look at figure 12. The picture 12 A shows the symbol for fuse. The picture 12 B shows the symbol for a circuit breaker.
CLASS WORK ASSIGMENT : LESSON A
The following exercises should be completed in class with the instructor’s assistance .
1. Look at figure 1. Fill In the blanks below. a. indicates a _
_____ _______
b. Indicates a ___________ c. indicates a ______________________ d. indicates the ___________ __ e. indicates the ______ _____________ f.
Indicates the _________ _ ________
ELECTRICITY SPECIALIZED ENGLISH COURSE
P8nn 103
2. What opposes current in a conductor ?
3. What is EMF or voltage ?
4. When is heat produced in a wire ?
5. When ______________________ increases the amount of heat ________________ too. Ail conductors can not ____________ the same _______________ of current. The amount of current that a __________________ can _____________ _has been calculated or _______________________ .
6. What happens in a circuit, when current exceeds the predetermined value ?
7. What does excessive current cause in a circuit ?
8. What is the purpose of a fuse ?
9.
ELECTRICITY SPECIALIZED ENGLISH COURSE
In order to protect the circuit against
P8nn 104
___ current we use a __________ , it is the can_______________ .
___________________________________ _______ . The ______________ has a ___________ _ amount of cunent a When the current ___________________ the _____________________ of the fiise, the wire in it will _______________ and ___________________ the circuit. Also we can say the fuse will ____________ .
9.
ELECTRICITY SPECIALIZED ENGLISH COURSE
10. if a fUse can not cany more than 15 amperes, what is its rating ?
11.
When will the wire in the fUse melt and open the circuit ?
12.
When will a fUse blow ?
14. what are the names of the two types of fuses we have talked about ? 13. Will current flow in a circuit with a blown fUse ?
15. What type of fuse fits into the clips on the fuse block ?
16.
What is the purpose of a circuit breaker ?
17.
Can a fuse be reset ?
18.
What protects circuits from excessive current ?
19.
How do you reset the circuit breaker ?
Page
105
ns:
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
Page 106 UNIT EIGHT
RESISTORS AND TRANSFORMERS
OBJECTIVES
1.
The student wNI be able to state the purpose of a resistor correctly
2.
Given pictures of a number of resistors, the student will orally and/or In writing identify correctly the following features :
• fixed resistor • variable resistor • adjustable resistor
3.
Given a picture,the student will
write the names of the electrical symbols listed
below: * •
switch
•
battery
variable resistor
• adjustable resistor
• fixed resistor
4.
Given a task the student will orally and/or in writing state purpose of a step-up transformer.
5.
Given a task the student will orally and/or in writing state purpose of a step-down transformer.
6.
Given a task the student will orally and/or in writing state purpose of a power transformer.
7.
Given diagrams of various transformers the student will orally and/or in writing Identify the following features :
• primary coH
• step- down transformer
• secondary coil
• power transformer.
• step-up transformer
•
winding
S&I
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
Page 107
UNIT EIGHT
RESISTORS AND TRANSFORMERS
LESSON A 1.
RESISTORS
Resistance opposes current in a circuit. Remember, current and resistance are inversely proportional. When resistance increases, current decreases. Look at figure 1, Symbol A represents a battery, symbol 8 represents a fuse, symbol C represents a switch.
Now, let’s talk about resistors, look at figure 2. It is a picture of a resistor connected in a circuit. The
<
c—i Resistor
<3^0 ---------CT\JD— Figure 2
resistor controls the amount of cunerrt flow in the circuit.
Page
ELECTRICITY SPECIALIZED ENGLISH COURSE
Let’s see how a resistor controls current flow in a circuit. Look at figure 3. The water pipe has a valve connected to It. The valve controls the
amount of
water that flows
through the pipe. The amount of water that flows through the pipe can de increased or decreased by opening or closing the valve.
Now, compare the resistor with the valve. First, think of current as the water flowing through the pipe. Then, think of the valve as a resistor. You increase or decrease the water flow by opening or closing the valve. You increase or decrease current flow by decreasing or increasing the size of the resistor. Look at figure 4 A. It is a series circuit with one resistor. The battery voltage is 12 volts. The resistor has a resistance of 3 ohms. You already know that by using Ohm’s law you can determine the amount of cunent flow in the circuit, which is 4 amps.
108
I S&&1
ELECTRIC ITT SPECIAL DEED ENGLI8H COURSE
Page
109
Now. Look at figure 4 B. This circuit has a 12 volt battery. The resistor is larger than the resistor in 4 A. It has a resistance of 6 ohms, so the current in the circuit is Just 2 amps. Current decreases when you increase the size of a resistor. Look at figure 4 C. The circuit has a 12 volt battery and a 2-ohm resistor. There is a current of 6
c-
6 Ohms 12 Volts
I?
'O ----- cf\_o— 2 Ohms
12;
y
_ l ~4
i?
Volts
- 2 Amps
-0
=6 Amps Figure 4C
amps in the circuit. Current increases when resistance decreases. Remember, the purpose of a resistor is to control the amount of current in a circuit.
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
Page
110
Now, you will learn different types of resistors. Look at figure 5. This is a fixed resistor, the amount of resistance can not be changed in this type of resistor. Look at figure 6, this is the symbol for a fixed resistor
Look at figure 7. This is another type of resistor. It is an adjustable resistor. The amount of resistance can be changed in this type of resistor.
Look at the adjustable resistor in figure 8, H has a sliding collar . The sliding collar is moved along the adjustable resistor to change the resistance.
Remember, the fixed resistor is used in a circuit where you want the resistance to stay the same; an adjustable resistor is used in circuits where you want to change the resistance from time to time.
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
Page
111
Look at figure 9. This is a variable resistor. A variable resistor is used in circuits when the resistance must be changed frequently. In figure 10, there is a variable resistor. You can observe here the knob. The resistance can be changed in a circuit by turning the knob.
The symbols for these three types of resistors that we've learned are shown In figure 11. 11 A shows the symbol for a fixed resistor. 11 B shows the symbol for an adjustable reslstor.11 B shows the symbol for a variable resistor.
Variable Resistor Figure 11 ___________
Page
ELECTRICITY SPECIALIZED ENGLISH COURSE
UNIT EIGHT
CLASSWORK ASSIGMENT : LESSON A
The following exercises should be completed In class with the Instructor’s assistance: 1.
Look at figure 1.
<±
It is a __________________ circuH. a.
Indicates the____________________
b.
Indicates the ___________________
c.
Indicates the ___________________
d.
Indicates the ___________________
2.
What opposes current in a circuit ?
3.
What is the purpose of a resistor ?
4.
Current and __________________ are _____ ___________________ increases, current:
proportional, so when . A larger resistor a
_____________ current in a circuit.
5.
If I have a circuit with 24 volt battery, a 10-ohm resistor, what is the current flow ?
112
I d&i 6.
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
Look at figure 2
They are three _____ a.
indicates a ____
b.
indicates an ___
c. 7.
indicates a ____ Which resistor Is used when you want to change the resistance from time to time ?
AAA/
L
c.
8.
---- \AVV
Figure 2 When Is a variable resistor used in a circuit ?
Page 113
Page 113
ELECTRICITY SPECIALIZED ENGLISH C0UR8E
I 9. In a
resistor, the
the
. In an
be
bv
can be chanaed bv tumina resistor the
can the collar alone the
resistor
10.
What is a resistor called in which the amount of resistance can not be changed ?
11.
What is the difference between a variable resistor and an adjustable resistor ?
12.
Look at figure 3. Wriie the name for all symbols in figure 3.
a.
represents
a ______________________________ .
b.
represents
a _____________________________
c.
represents
a ______________________________ .
d.
represents a __________________________________________
e.
represents an_________________________________________
f.
represents a __________________________________________
.
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page
UNIT EIGHT
RESISTORS AND TRANSFORMERS
LESSON B 1. TRANSFORMERS In the fast lesson we talk about flises. This lesson we will deal about transformers. But before we talk about transformers let’s review induced voltage. Look at picture 1. Circuit A is connected to an AC power source and the switch is open. There is one coil connected in circuit A. Circuit B is not connected to a power source.
MAGNETIC FIELD CIRCUIT A
Figure 1
CIRCUIT B
CIRCUIT A
CIRCUIT B
Figure 2
Now, look at figure 2. Let’s see w hat happens when the switch in circuit A is closed. When switch In circuit A is closed current flows. When current flows through coil A, a magnetic field is produced around coil A. The magnetic field of coil A induces a voltage in coil B. The induced voltage in coil B causes current flow in circuit B. Look at the direction of current flow in the circuits. The current in circuit B and circuit A flows in opposite directions.
114
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 115
Look at figure 3. The current in circuit A has changed direction, so the current in circuit B also changed direction. Remember the magnetic field of coil A induces voltage in coil B. This induced voltage causes current flow in circuit B. This induced voltage is necessary for the operation of a transformer. A device that changes high voltage to low voltage or low voltage to a high voltage Is a transformer . Let’s talk about some of the words used in discussing transformers. Look at picture 4. Each loop of
CIRCUIT
A
CIRCUIT
B
Figure 3
wire in a coil is a turn. Coil A has 6 turns. Coil B has 4 turns. Another name for the turns of a coil is windings .
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page
Let’s take a look at a transformer. Look at figure 5. There are two coils. The coil connected to the power source is called the primary coll. The current from the power source flows through the primary coil. The current causes a magnetic field around the primary coil. The magnetic field of the primary coil induces a voltage in the secondary coll. The primary coil has more turns , it has 6 turns or windings. The secondary coil has 3 turns. An input voltage of 100 volts is applied to the primary coil. The output voltage of the secondary coil is 50 volts. Okay, when the primary coil of a transformer has more turns than t he secondary coil, the output voltage is less than the input voltage. The transformer in picture 5 is a step-down transformer. A step-dow n transformer changes a high voltage to a low voltage. A step-down transformer has more turns in the primary coil than in the secondary coil.
Look at figure 6. This is a step-up transformer. A step-up transformer changes a low voltage to high voltage. In a step-up transformer, the secondary coil has more turns than the primary coil.
116
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
Page
117
Remember the turns of a coil are often called windings. The word winding is also used when talking about the primary and secondary coils of a transformer. Instead of saying a transformer has a primary coil and a secondary coil, you can say a transformer has a primary winding and a secondary winding
A transformer can either step up or step down a voltage. Look at figure 7. This is a power transformer. A power transformer is used either to step up or step down an AC voltage having a power frequency of 60 cps.
Figure 1 - Power transformer
Look at figure 7 again. This transformer has one primary coil and three secondary coils. The input voltage of the primary coil is 110 volts AC. The output voltage of secondary coil A is 6,3 volts AC. The output voltage of secondary coil B Is 350 volts AC. The output voltage of secondary coil C is 5 volts AC.
So, this power transformer is both step-up transformer and step-down transformer. Coil B in the secondary steps up the voltage; coils A and C step down the voltage. A power transformer is used in communication equipment.
Page
ELECTRICITY SPECIALIZED ENGLISH COURSE
UNIT EIGHT
CLAS8WORK A88IGMENT : LE88ON B
The following exercises should be completed in class with the instructor’s assistance. 1.
What produces a magnetic field around a coil ?
2. When a voltage is _____________________ in the secondary current ______________ in the circuit B. The ___________
____ , it causes __ in circuit A
(primary) and circuit B (secondary) flow s in ______________
directions. If the In
current in circuit A changes direction , the _______________
circuit B also
direction.
3. What is a transformer ?
4. What is each loop of wire called ?
5. What Is another name for turns of a coil ?
6. The ________________ that is connected to the __ __________________ . The ______________ ___________________ voltage.
7. What are other names for primary coil and secondary coils ?
_ source is called coll has an
118
L-jfib.
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
Page
119
ELECTRICITY SPECIALIZED ENGLISH COURSE
Figure 1 B Figure 1 C Figure 1
8.
Look at figure 1 A. Fill in the blanks below.
They are three_________________ . __________ a.
indicates the __________________________
b.
indicates the __________________________
c.
indicates the __________________________
d.
indicates the __________________________
e.
indicates the __________________________
Page
120
LJAL
ELECTRICITY SPECIALIZED ENGLISH COURSE
9.
Look at figure 1. Complete the following exercises.
•
Figure 1 A is a ________________________________
•
Figure 1 B Is a __________ . ____________________
•
Figure 1 C is a ________________________________
10. A steo-up
changes a voltage.
In this type
coil has
Page 121
voltaae to a of transformer the turns than the
coil.
11.
A _______ _________________ transformer either __________
______________ or
___________________ ________ a voltage.
12.
A _____________ ___________ transformer a high voltage to a ______________________ voltage. The secondary coil has ______________________ turns than the _____________________ coll.
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
’ Page 122
UNIT NINE
POWER AND ELECTRICAL SAFETY
OBJECTIVES 1.
Given a task the student will orally and/or in writing define the following two ratings found on electrical equipment:
• voltage rating • power rating
2.
Given a task the student will be able to Identity and use the following prefixes and electrical units:
•
kilo
•
mega
•
watt
•
Kw.
•
Mw.
3.
Given a task the student wilt define correctly the following terms :
• live conductor • hot wire • warning sings •
dry insulating material
• electrical shock •
tourniquet
• serious injury
4.
Given a task the student will orally and/or in writing explain what happens when someone touch a hot wire.
I s£5n
SENAl
Page 123
ELECTRICITY SPECIALIZED ENGLISH C0UR8E
UNIT NINE POWER AND ELECTRICAL SAFETY
LESSON : A 1. POWER From your own experience you have probably found that electrical equipment is rated for both voltage and power. The unit of electrical power is the watt. Look at figure 1. The markings on a soldering iron are 110v and 200w. The marking 110v is the voltage rating and the marking 200w is the power rating. Instead of saying power rating, a more common expression is wattage rating .
Look at figure 2. Each light bulb has the same voltage rating but a different wattage rating. The wattage rating of bulb A is 75 watts. Light bulb B has a wattage of 150 watts. Light bulb “B” has a higher wattage rating than light bulb "A”. Look at the figure 2 again and notice the brightness of each light. Light bulb "B” burns brighter than light bulb “ A". So more light is furnished by a light bulb w ith a higher wattage rating.
1 dfifen
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 124
The wattage rating of electrical equipment indicates the rate of doing work, the rate of at which electrical energy is changed into heat or light. Power Is the rate of doi ng work. The higher the w attage rating the higher the rate of doing work. The watt is the basic unit of measurement for power.
Look at figure 3. The faster a lamp changes electrical energy into light energy, the brighter the light will be; a 150-watt lamp furnishes more light than a 75-watt lamp.. Look figure 3 again. Electric soldering irons are made of various wattage ratings with the higher watt irons changing electrical energy to heat energy faster than the lower watt irons.
POWER RATING OF EQUIPMENT IS THE RATE
\ \
AT WHICH IT CHANGES
\
ELECTRICAL- ENERGY INTO ....................
-)
HEAT OR LIGHT 73 WATTS
GREATER WATTAGE FURNISHES MORE HEAT AND LIGHT.
Figure 3
1,
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
Page 125
Remember, the watt is the basic unit for electrical power. When the basic unit, watt, Is too small, It must be expressed in a larger unit. Names and abbreviations have been devised to indicate multiples. The name of the multiple 1000 is kilo and its abbreviation is "k”.
Names of larger units are derived by using a prefix with the basic unit. Kilowatt is a larger unit. One kilowatt Is 1000 watts. To express 1 kilowatt using abbreviations you would say *1 kw”; kilo is k, snd watt Is w.
“Mega" is another prefix used to express a larger unit. Mega is the prefix meani ng million. Let’s attach the prefix mega to the unit watt. Then, we have megawatt meaning one million watt. The abbreviation for rnega is tha capital letter "M*.
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
Page 126
UNIT NINE
CLA8SWORK A88IGMENT : LESSON A
The following exercises should be completed in class with the instructor’s assistance. 1.
What is electrical equipment rated for ?
2. Is the unit of electrical power the volt or the watt ?
3.
The __________________ Is a ________________ of electrical __________________ . Its abbreviation Is ________ . All electrical equipment is _______________________ for both _________________ and ___________________________ . Another name for _____________________ rating is ____________ rating.
4.
Is more light furnished by a light bulb with a lower or higher wattage rating ?
5.
What does the wattage rating indicate ?
6.
Does the higher or lower watt lamp change electrical energy to light faster ?
7.
Does a lower wattage iron change electrical energy to heat faster than one of a higher wattage rating 7
L_s£2h
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
8.
How is power rating more commonly referred to ?
9.
When is larger unit used ?
10.
The name of multiple 1000 is ___________ ___ . ___________________ is another _
Page 127
and its abbreviation is __ used to express a
___________ unit. It is a prefix that means
11.
What does kilo mean ?
12.
How many watts does one kilowatt equal ?
13.
What prefix means million ?
14.
What is the abbreviation for mega ?
15.
Write the following numbers using the prefixes that we have dealt in this lesson.
•
453 987 123 watts ________________________________________________________
•
108 352 789 volts _________________________________________________________
•
453 123 987 ohms
I s&n
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 128
UNIT NINE
POWER AND ELECTRICAL SAFETY
LESSON B 1. ELECTRICAL 8AFETY In previous lessons we talked about many of the wonderful things that electricity can do for us. But this period we will talk about some of the bad things electricity can do to us. There is one thing you should remember about electricity : electricity can be dangerous . Electricity can cause serious injury and death.
Look at figure 1. Let's see how electricity can cause serious injury and death. Serious injury and death can be caused by electrical shock. Electrical shock is caused by electric current flowing through the body. In figure 1, the man Is receiving an electrical shock. He is receiving an electrical shock because he is touching an insulated hot wire. A hot wire is a conductor through which current is flowing. Another term for hot wire Is live conductor .
Figure 3
ELECTRICITY SPECIALIZED ENGLISH C0UR8E
Page 129
Let’s talk about some of the things you can do to avoid an electrical shock. Look at figure 2. You should not wear rings, watches or metal objects while performing maintenance on electronic equipment.
Now, the reason you should not wear these objects is this. Rings, watches and metal objects are conductors and they can cause an electrical shock.
Let’s look another precaution you can take to avoid electrical shock. Look at figure 3. Make sure the power is turned off before working on electric equipment.
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
Page 130
Look at figure 4. It is a w arning sign. The sign says danger - high voltage. T he sign, danger - high voltage, is a warning sign. You must be careful working around high voltage. High voltage can kill you.
/
—— .. . ................................ . ... .......... ..... ............................... “\
AW ARNING ^■v
•
Hazardous voltage. Backfeed to utility system i can cause electrocution or property damoge.
When generator is used for standby power, use of automatic transfer switch is recommended to prevent inadvertent interconnection of standby and norma! sources of supply. 25BB15 J
Figure 4.- Warning sign
Warning signs should be posted in all areas where high voltage is used. Warning signs indicate danger. There are many safety rules, but one you should always remember is be careful .
No matter how many safety rules are written accidents continue to happen. So let’s talk about some of the things you can do when you seen an accident involving electrical shock. The victim of electrical shock depend on you to give him/her first aid.
In case of an accident involving an electrical shock, the first thing you can do is turn off the high voltage. If you can not turn off the high voltage you must free the shock victim from the live conductor.
I
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 131
Let’s see how you can free a shock victim from a live conductor. Look at figure 5. Remember this : DO NOT TOUCH THE VICTIM with your bare hands. If you touch the victim with your bare hands you will receive an electrical shock. In order to free the victim from the live conductor you must protect yourself with dry insulating material. Examples of dry insulating material you can use are : a dry board, your belt and dry clothing.
DO NOT TOUCH VICT
IM WITH YOUR
BARE HANDS.
ELECTRICITY SPECIALIZED ENGLISH COURSE
Page 1 3 2
Let’s talk about first aid. You should administer first aid after the victim is freed from the live conductor. The two most likely results of electrical shock are : the victim stops breathing and receives bodily injury from falling.
Let’s see what type of first aid you can give a shock victim. Look at figure 6. If a person is bleeding you must control the bleeding. Bleeding can be controlled by using pressure or a tourniquet. In figure 6 A, pressure is being used to control bleeding and a tourniquet is being used to control bleeding In figure 6 B.
Figure 6 - Control bleeding Figure 5
ELECTRIC ITT SPECIALIZED ENGLISH C0UR8E
Page 133
Now let’s see how can get the victim breathing again. Look at figure 7. If the shock victim is not breathing begin artificial respiration immediately. Artificial respiration is used to get the victim to breathe. In figure 7 you can notice the steps involved in giving artificial respiration. Repeat steps *F" and “G" at the rate of 12 to 20 times per minute. Continue this until the victim starts breathing Here is another thing to remember about blowing into a victim’s lungs. Blow forcefully
PLACE
THE
HEAD
AS
FAR
BACK
AS
PLACE YOUR THUMB IN THE
POSSIBLE SO THAT THE FRONT OF THE
CORNER OF THE MOUTH AND HOLD
N EC K IS S T R E TC HE D .
THE LOWER JAW UP.
Figure 7 .- Artificial respiration
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
into adults, and gently into children.
Page 134
Page 135
ELECTRICITY SPECIALIZED ENGLISH COURSE
UNIT NINE CLA8S WORK AS8IGMENT : LE88ON B
The following exercises should be completed in class with the instructor’s assistance : 1. What should you remember about electricity ?
2. What causes electrical shock ?
3.
4. A
What is a hot wire ?
conductor or ____ is
wire is a conductor through which
.
5.
What happens when you come In contact with a live conductor ?
6.
What shouldn’t you wear while performing maintenance on electric equipment ?
7.
What must you do before working on electric equipment ?
Page 136
ELECTRIC ITT SPECIALIZED ENGLISH COURSE
8.
______________ , ____________________ and are conductors and they can __________________________________________
9.
an electrical
What do warning signs indicate ?
10.
What is the first thing you can do to help a shock victim ?
11.
What must you do if you cannot turn off the high voltage ?
12.
What should you remember when you are freeing a victim from a live conductor ?
13.
While freeing a shock victim from a hot wire, how do you protect yourself ?
14.
What are some dry insulating materials you can use to free a shock victim ?
15.
What are two results of electrical shock ?
16.
How can bleeding be controlled ?