E-text prepared by Kevin Handy, John Hagerson, Matthew Wheaton, and the
Online Distributed Proofreading Team (http://www.pgdp.net)
Note: Project Gutenberg also has an HTML version of this
file which includes the original illustrations.
See 38036-h.htm or 38036-h.zip:
(https://www.gutenberg.org/cache/epub/38036/pg38036-images.html)
or
(https://www.gutenberg.org/files/38036/38036-h.zip)
Idaho Agricultural Extension Service
Bulletin 396
June, 1962
T-1
ELECTRICITY FOR THE 4-H SCIENTIST
Safety
Uses
Economy
Division I
4-H Electric
University Of Idaho
College of Agriculture
HOW TO USE THIS BOOK IN FULFILLING THE GOALS OF THE 4-H ELECTRIC PROJECT
FOR THE FIRST AND SUCCEEDING YEARS
The minimum goals for credit in the 4-H Electric project vary according
to the 4-H member's age and the number of years he or she has taken the
electric project. For example, if you are a 4-H member beginning the 4-H
Electric project at the age of 10, you will not be required to earn as
many credit points as a 14-year-old 4-H member beginning the 4-H
Electric project. However, if you are a 12-year-old in your second year
of electricity you must earn as many credit points in that year as a
14-year-old does in his or her first year.
Each lesson or goal has been designated a certain number of credit
points. These are shown near the title of each lesson or goal. You
decide on the lessons you want to study, list them, and add up the
credit points.
For a full year's 4-H project credit, the total of your credit points
should be at least as many as shown in the following table:
Examples of reading the table below are as follows: (a) An 11-year-old
member is required to complete 13 credit points the first year, (b) A
14-year-old is required to complete 17 credit points his first year, (c)
A 14-year-old taking the electric project for the third year must
complete 16 credit points that year.
We recommend that, if you are taking the 4-H Electric project, you start
with the first lesson in the book and go on through to the back of the
book in advanced years. But you may skip the less important or less
interesting parts so long as you learn the basic lessons. A way to find
out whether you know the basic lessons is to read them through and try
to answer all questions under the heading "What Did You Learn." If you
can answer these questions you may not wish to spend the time doing the
things listed under "What To Do."
Minimum Number of Credit Points Required for Each Year's Work in
the 4-H Electric Project
4-H Member's| 4-H Member's Year in 4-H Electric Project
Age |
| 1st Year | 2nd Year | 3rd Year | 4th or
| | | | Later Years
10-11 | 13 | 15 | |
12-13 | 15 | 17 | 19 | 20
14-15 | 17 | 19 | 21 | 21
16 & over | 19 | 21 | 21 | 21
This system of credit points makes it possible for you to do the things
you want to do with electricity and get credit for them in the 4-H
Electric project.
4-H Electric, Division I
TABLE OF CONTENTS
Lesson Credit Page
Number Title Points Number
How to Use This Book 1
B-1 Getting Acquainted With Electricity 3 2
B-2 Tools for Electricians 4 7
B-3 Rewire a Lamp--Be a Lamp Detective 3 11
B-4 Make a Trouble Light 3 15
B-5 What Makes Motors Run 5 18
B-6 Taking Care of Electric Motors 3 23
B-7 Reading the Electric Meter 4 26
B-8 Ironing is Fun 3 30
B-9 Let's Be Friends With Electricity 2 35
B-10 How Electric Bells Work--For You 3 39
B-11 First Aid for Electrical Injuries 2 43
B-12 How Electricity Heats 3 47
B-13 Mysterious Magnetism 2 50
B-14 Give Your Appliances and Lights a
Square Meal 2 54
B-15 You Can Measure Electricity 4 58
UNIVERSITY OF IDAHO
COLLEGE OF AGRICULTURE
AGRICULTURAL EXTENSION SERVICE
Eric B. Wilson, Extension Agricultural Engineer
1962
Published and distributed in furtherance of the Acts of May 8 and June
30, 1914, by the University of Idaho Extension Service, James E. Kraus,
Director; and the U. S. Department of Agriculture, Co-operating.
LESSON NO. B-l
Credit Points 3
GETTING ACQUAINTED WITH ELECTRICITY
Electricity serves you best when you understand how it works and use it
properly. As a 4-H member, you should know about electricity and help to
show others the way to obtain its tremendous work-saving benefits as
well as how to use it with safety.
A good way to think of electricity is to compare it with water. It acts
a lot like water. However it is made of tiny parts of atoms called
electrons. When there are more than the normal number of electrons in
anything, it is said to be negatively charged; when there is a shortage
of electrons, it is positively charged. As water flows downhill,
"seeking it's level," electrons flow from negative to positive, seeking
to "balance" the charge.
Electrical Conductors
Even if you're never going to repair a lamp or make a chick brooder, you
should know about conductors and insulators. This is because you happen
to be a fairly good conductor of electricity. Electricity will pass
easily through you to other conductors--the ground, for instance. When
this happens you may get a shock, burn, or serious injury. But it
doesn't ever have to happen, if you learn to understand your friend,
electricity.
Silver, copper, iron, aluminum and many other metals are very good
conductors. Water, acids, and salts are too. Electricity passes over or
through them very easily. Like water pipes, the larger the conductor,
the more electricity it can carry. When conductors are too small for the
amount of electrons trying to move over them, they get hot, melt, may
start fires. That's why wire size is important.
Electrical Insulators
Insulators are the opposite of conductors. Electricity has trouble
passing through some materials. Rubber, most plastics, dry wood, oils
and glass are some of the good insulators. It's the amount and kind of
insulation that counts. If it has enough force, electricity can pass
through just about anything--even jump gaps!
Electricity, like water, flows along the easiest paths. It is always
trying to get to the ground. The earth attracts it. It stays on the
wires unless a person, a wet branch, or some other conductor gives it a
path to the ground. Do not touch any wire which might be carrying
electricity.
Play It Safe
If you should touch a "hot" wire accidentally and are standing on a dry
piece of wood, the conducting pathway to the ground is not good and the
electricity may keep running along its wire. But do not touch some other
conductor with another part of your body. This would complete a circuit
through your body and would be very dangerous. Always make sure there is
plenty of good insulation material or plenty of distance between you and
anything which might be carrying electricity.
Remember, too, insulation is of little use when it is wet. Dew, mist,
rain, condensation, a damp floor can change the whole picture. If you
understand electricity and how it acts, you'll be safe enough, because
you won't take chances or expose yourself to injury.
Electrical Terms
_Alternating Current_--Usually referred to as "AC," alternating current
is current which reverses its direction of flow at regular intervals, 60
times a second.
_Direct Current_--"DC" current flows only in one direction. Battery
current is DC.
_Ampere_--Amperes are units by which the rate of flow of electrical
current (electrons) is measured. An ampere is 6.3 billion electrons
passing one point in a circuit, in one second. This compares with the
way the flow of water is measured in gallons per second.
_Volts_--A volt is a unit to measure the tendency of electrons to move
when they are shoved. Voltage is the amount of "push" behind the
electrons. It's like water pressure in a pipe. Home power lines carry
115 volts (110 to 120 volts). For appliances such as electric stoves,
washers and driers, a second 115-volt line should be added, giving 230
volts (220 to 240 volts).
_Watts_--Watts equal volts times amperes. Light bulbs, electric irons
and other appliances are usually marked with the voltage they require
and the number of watts.
_Kilowatts_--Your electric bill usually reads in kilowatt hours. A
kilowatt is 1000 watts. A kilowatt hour equals 1000 watts used for 1
hour. One kilowatt equals about 1-1/3 horsepower. A kilowatt is usually
indicated by "kw" and a kilowatt hour by "kwh."
_Circuits_--A closed circuit is one in which the electricity is flowing,
lighting a light, running a motor, or some other appliance. The circuit
runs all the way from the place the electricity is being generated to
your home, through the appliance or light bulb, and back to the
generator.
Circuits are opened and closed by switches. When the circuit is opened,
the electricity stops at the switch. Before working on a switch, socket,
fuse, or any part of the wiring be sure to open the main switch. The
main switch is usually at the fuse box or near it. Appliances should be
disconnected when you work on them. Everyone in the family should know
where the main switch is so it can be pulled in case of accidents, fire,
flood, or windstorm damage.
_Fuses and Circuit Breakers_--These are the safety valves of your
electrical system. The different electrical circuits in your home are
meant to carry only certain amounts of electricity. Some carry only 15
amps, others can carry 20 or more. They are marked to show capacity.
When a fuse burns out or a circuit breaker opens, look for an overload
of lights and appliances on the circuit before you try to replace the
fuse or close the circuit breaker. Without these safeguards, the
overloaded electric line will heat up and may start a fire. Even if no
fire starts, electricity will be wasted and the homeowner will be paying
for electricity that's doing no good.
Remember: If you ever have to replace a fuse, pull the main switch
first. Keep a flashlight handy in your house. It seems that fuses
usually blow at night, and it doesn't pay to stumble or fumble around
electric wires in the dark.
WHAT TO DO: Make A Circuit Board
So that you can show others how electricity travels from here to there,
and how it behaves under different conditions, make an electric circuit
board.
_Materials Needed:_
Piece of 3/4" board about 4" x 6"
l-l/2-volt No. 6 dry cell battery
Two pieces of bell wire, each 24" long, one black, one white
Two 10-penny box nails (3")
Three 3-penny box nails (1")
Two small screws or carpet tacks
Two 2-inch rubber bands
Two miniature sockets with solder terminals
Two l-l/2-volt flashlight bulbs
_Tools Needed:_
Ruler, pencils, hammer, pliers or vise.
_Making the Board:_
1. Lay out the board with a pencil and ruler as indicated in Figure 1.
2. Bend the three-inch nail as shown in Figure 2, using pliers, vise and
hammer.
3. Pound the one-inch nails into the board for a half-inch at points A,
C, and D. Use the three-inch nail to make a hole a half-inch deep at B.
Put the crank nail in this hole and pound in a little farther. Attach
the lamp socket brackets at E and F. Stretch the rubber band as in
Figure 3.
4. Lay out the electricity path, the circuit (Figure 3). Use the black
wire for the positive side of the circuit (the center pole of battery).
Twist it around the switch crank B, and the center pole of battery. Run
another piece to the outside terminal of bulb socket at E. Run white
piece to negative pole of battery from the other terminal at E.
[Illustration: Figure 1 (Circuit Board)]
[Illustration: Figure 2 (Switch)]
5. Close the switch. The rubber band should hold the switch nail tightly
against nail at C. Does the bulb light? __________ If it doesn't, check
the connections.
Now you have a circuit--a closed circuit when the electricity runs all
the way from the positive pole to the negative pole. The black wire is
the hot side, the live wire, because it carries the full load of the
battery up to the bulb.
Remember, battery current is direct current, DC. In the case of
alternating current, AC, such as most homes and buildings use, the
electricity flows in first one direction and then the other.
[Illustration: Figure 3 (Closed Circuit)]
Parallel Wiring
To make this circuit hookup, attach another white wire to the negative
pole of battery and a terminal of the second flashlight bulb. Run a
black wire from the other terminal to the switch terminal at C (Figure
4). Close switch. Both bulbs will light.
Trace the circuit. Electricity is going equally to each bulb, the same
amount that went to the single bulb. The difference is that the battery
will last only half as long. It's like a pail of water with two open
spigots. The pail empties twice as fast as it would with just one spigot
open. This type of wiring is called parallel wiring. If one bulb is
unscrewed, the other will stay lit.
[Figure 4 (Parallel Wiring)]
Series Wiring
To do this, run the negative wire to one terminal of the second bulb and
attach a wire from the other terminal to a terminal of the first bulb.
The other terminal connects with the switch at C (Figure 5). This is
series wiring. If one bulb is unscrewed, the other will fail to light
because the circuit is broken for both. Anything that breaks the circuit
has the effect of opening the switch.
[Illustration: Figure 5 (Series Wiring)]
Show there is a circuit through the bulb by screwing and unscrewing it.
Also, "jump" the socket by running the wire from C to the other terminal
of the bulb at E while it is unscrewed. Bulb at F will light. Trace this
circuit.
SUGGESTED DEMONSTRATIONS
Using the Circuit Board, you can give many demonstrations of the way
electricity flows, works and behaves.
Water And Electricity
To help others understand electricity better, draw a water system on an
electric circuit board paralleling the circuit. For the battery show a
water tank, pipes instead of wires, faucets instead of switches.
Somewhere on the board paste a comparison of electrical terms with terms
used in describing water, such as the following:
Wire equals Pipe
Volts equal Pressure
Amperes equal Rate of Flow - gallons per second
Watts equal Pressure times Rate of Flow
Switch equals Faucet
Current equals Flowing Water
Show how to figure the wattage that a circuit protected by a 15 ampere
fuse can handle. Do it with actual things or cut-out pictures of light
bulbs, irons, toasters, coffee-makers, etc.
You know that Amperes times Volts equal Watts. If the voltage is 115, a
15 amp circuit can handle 115 volts times 15 amps, or 1725 watts.
The name plates on electric motors indicate the amperage at full load.
You can convert this to watts, of course, by multiplying amperage by the
line voltage. Motors require an additional amount of electricity when
they start. You need to allow for this fact, so fuses will not blow or
circuits trip when a motor is turned on. You will learn more about this
when you study electric motors.
For More Information
Your leader has many other sources of information about electricity and
demonstrations you can perform. Ask him. Also, libraries have many books
about electricity and its history, which are very interesting and
useful. Maybe you can find an electrician, someone from your power
supplier, or an equipment dealer who will talk to your club on
electricity or electrical safety.
What Did You Learn?
(Underline the correct answers then discuss in the group.)
1. In a water pipe system water flows. In an electrical circuit
(electrons) (atoms) (charges) flow.
2. Electricity or electrons flow (easier) (harder) (about the same) in a
conductor than in an insulator.
3. Rubber is a good (conductor) (insulator) (ground).
4. The most common material used as an electrical conductor is (glass)
(silver) (copper).
5. The unit of electrical pressure or push is the (ampere) (volt)
(watt).
6. The rate of flow of electricity is measured in (gallons) (amperes per
minute) (amperes).
7. Volts times amperes equals (watts) (kilowatt hours) (alternating
current).
8. A dry cell battery (stores) (makes) (uses) electrical energy.
9. In a parallel circuit the electricity has (one) (two or more) (no)
paths to travel.
10. In a series circuit with two bulbs and a switch the bulbs are
(brighter) (dimmer) (the same) as when they were in the parallel
circuit.
LESSON NO. B-2
Credit Points 4
TOOLS FOR ELECTRICIANS
Who goeth a borrowing
Goeth a sorrowing
Few lend (but fools)
Their working tools
Tusser 1524-1580
Whenever a job comes up, it saves time and trouble when you have the
right tools and they are all where you can find them. Electrical work
takes some special tools and some everyday tools.
If you have ever watched a good electrician at work, you've seen how
neatly he stores his tools in a box so every one of them is handy. When
a lineman climbs a pole, he has his regular tools in a holster on his
belt. Special tools are kept in a box in racks in the repair truck, all
ready for instant use. Wouldn't you like to have electrician's tools all
handy, ready for use, and know how to use them properly?
Basic Tools for Electrical Work
_Knife_
A good knife with a sharp blade is one of the most useful tools. A
camper's or electrician's type knife is probably best because it has
other useful parts besides the cutting blades--a screwdriver or punch,
for instance. Of course, you'll never use the cutting blades as a
screwdriver. This knife should be kept clean, dry, sharp, and free from
rust. Put a little oil on the joints from time to time. Remember, "Never
whittle toward you and you'll never cut yourself."
_Pliers_
A pair of electrician's pliers should be part of your kit. Wrap the
handles with plastic insulating tape. Even though you're not going to
work on "hot" electric lines, it pays to play safe. Later on, as you
learn more about electricity, you'll want a pair of needle-nose pliers
for the fine work.
_Screwdrivers_
You'll want a screwdriver which has true corners. A 4 to 6 inch plastic
handled screwdriver with a narrow blade is best. You'll probably need
more than one size to fit the various size screws you'll be turning.
Screwdrivers are easily damaged if you try to use them as chisels and
pry bars, or use them in screw slots which are too large for the blade.
You can be hurt by the screwdriver if you try to screw or unscrew things
you are holding in your hand. Keep your free hand away from the end of
the screwdriver. Place the work on a bench or where it can be handled
easily.
_Soldering Iron_
A good 100 to 250-watt electric soldering iron will be useful. Later on
you may want to buy a soldering gun, but unless you are doing a lot of
soldering it won't be necessary. A supply of resin-core electrician's
solder will be needed. Acid-core solder reacts with copper and in time
causes a bad splice.
_Tape_
Once it was necessary to use two types of tape on splices--rubber tape
with friction tape over it. Now there is a plastic tape on the market
which takes the place of both and has good insulating quality. It is
called electrical tape, or plastic tape, and resists water, oils (which
would damage rubber tape), and acids. You'll need a lot of tape in your
electrical work, so keep a roll on hand.
_Other Tools and Equipment_
As you go along in electrical work, you'll be adding tools and other
equipment, such as a trouble light and maybe an ammeter or voltmeter.
Other tools you'll want to add will be a Phillips screwdriver, open end
wrenches, a crescent wrench, small hack saw, hand drill and bits.
You'll also be using some regular carpenter's tools such as hammers,
saws, and so on. Unless you use them frequently, you don't need to keep
them in your electrical kit.
It's a good idea to start acquiring a supply of electrical
parts--lengths of wire, fuses, switches, sockets, plugs, and other items
that will come in handy. There are parts you can salvage from old lamps,
motors, and other equipment. Such a collection can be a real treasure
chest when you need a part in a hurry. But be sure to throw away all
faulty parts.
[Illustration: Figure 1. Completed tool chest.]
WHAT TO DO: Build a Tool Chest
To keep your tools always ready for use, a tool chest will be very
handy. It's the 4-H way to work. You'll be surprised how much easier it
makes a job when you have your tools, various parts and repair equipment
all in one place. You can make the chest (Figure 1) with a saw, plane,
screwdriver, pencil, ruler or carpenter's square, and hammer.
_Materials You'll Need:_
A piece of lumber 1" by 10" by 8 feet long. (1" lumber is actually only
3/4" thick--this is the thickness you'll be working with.)
2 small hinges, with wood screws
1 small hasp, with wood screws
2 small handles with wood screws, or one large handle
1 small chain, 10" to 12" long
Some No. 6 penny finishing nails or wood screws about the same length
_Making The Chest:_
1. Cut your lumber into the following pieces:
1 piece 10" x 18" for top
1 piece 8-1/2" x 16-1/2" for bottom
2 pieces 6" x 8-1/2" for two ends
2 pieces 6" x 18" for front and back
2. Lay out pieces as shown in Figure 2.
[Illustration: Figure 2]
Then, set up the two end pieces and nail to bottom section. Refer back
to Figure 1 as you go along to see that box is shaping up as shown. Nail
the front and back sections to the ends along the bottom. Wood screws
can be used instead of nails.
3. Lay the top in place and attach hinges to the back side, about two
inches in from each end.
4. Attach one part of hasp to the top, and the other part to front board
in center. Fasten the handles to each end.
5. Attach chain to the top and front so the top will stay open when
chain is fully extended.
Now you can invent your own improvements for your chest. You can paint
it, put your name on it, and your club emblem and name if you wish. You
can put a rack on the inside of the cover to hold your work sheets and
other booklets and materials. You can install special slots or straps to
hold each tool in its place along the sides of the box. Maybe you will
want to put some partitions in the box to separate various electrical
equipment such as wires, fuses, switches, and plugs.
_A Working Kit_
An accessory which you may want to add to your tool chest is an apron or
holster to wear when you are moving around on the job. An apron can be
made of a size of cloth about 18 by 20 inches. It should be folded up
from the bottom, and sewn to fit the number and size of tools you have.
Figure 3 shows such an apron.
[Illustration: Figure 3. Apron.]
You can make a lineman's holster in the same way, using plastic or soft
leather. Merely make belt loops by cutting on the dotted lines. A snap
fastener will hold the flap over the tools so they won't fall out.
[Illustration: Figure 4. Lineman's Holster.]
Demonstrations You Can Give
Show and tell others the proper handling, care and use of tools.
Show and tell how to build an electrician's tool kit.
For Further Information
Ask your power supplier or an electrician to tell the club about the
various tools of the electrician's trade and demonstrate them. Ask your
leader how to get exhibit material or information about electrical tools
and their use and then tell the club about them.
LESSON NO. B-3
Credit Points 3
REWIRE A LAMP--BE A LAMP DETECTIVE
[Illustration: The Line-Up Of Lamp Suspects]
One of the duties of a law officer is to prevent crime. It's that way
with the lamp detective. You can become one. In the average home there
are lamps about to commit the crime of shocking people, starting fires,
and stealing electricity. Some are refusing to do their job well and
some are no-goods, sitting in closets or attics, doing nothing. You can
put these lamps to working again safely and well. Become the lamp expert
in your family.
What's In A Lamp?
A lamp gives light for comfortable and convenient use in the home. It
consists normally of a stand, switch, cord, lampshade holder, and shade.
Some lamps have diffusing bowls which reduce glare and shadows.
The most common fault found in an old lamp is in the cord, but sometimes
the switch or the wiring in the lamp is bad. Look over all the lamps in
your home and find the ones needing to be fixed.
WHAT TO DO--Rewire A Lamp
Somewhere around your house you can probably find a lamp that is no
longer used or needs repairing. You can make it useful again and at the
same time learn how to wire a lamp.
_Materials Needed_:
Tools: Pocket knife, small or medium screwdriver, and pliers
(electrician type is best).
_New Lamp Cord_: For each lamp to be rewired, you'll need 6 feet of cord
plus the length of wire within the lamp stand. Lamp cord wire comes in
two sizes, No. 18 and No. 16 AWG (American Wire Gauge). No. 18 is
smaller than No. 16, but is adequate for most lamps. Cords are made with
surface coverings of several different materials: braided cotton, rayon
or silk, and molded rubber or plastic. Braided cord is decorative, but
rubber or plastic is easier to work with and is usually more desirable.
_Switch_: If the switch is bad, get a new one. Socket switches are made
with push-through, turn-knob, or pull-chain controls. The pull-chain
type is seldom used on modern table or floor lamps. Your lamp may have a
separate push-switch in the base. In this case, get the same kind for
replacement. Some switches are "3-circuit" switches for use with high,
medium, and low-light bulbs.
_Plug_: Plugs are made of various materials, mostly hard rubber or
molded plastic. Some have a shank or handle for better grasping. This
type is more desirable. The plug on the old cord may be good, and if so,
may be used on the new cord.
How To Do It:
1. If the plug on the old cord is good and you plan to use it, remove it
from the old cord.
2. Measure and cut a new lamp cord equal to the length of the cord
within the lamp, plus 6 feet.
3. Pass one end of the new cord through the center of the plug. Strip 2
inches of the fabric insulation off cord, or in case of a rubber cord,
split cord back two inches. Be sure no bare wire shows in long split
section (Figure 1).
4. Use knife to strip insulation off wire for 3/4" on end of each cord.
Be careful. Don't cut yourself. Don't cut wires. Use a light touch,
slope the knifeblade and slice with knife edge away from you (Figure 1).
[Illustration: Figure 1 (Ready to Wire Plug)]
5. Twist exposed strands of each wire tightly to make a good conductor,
and place each conductor around its proper terminal in the direction in
which the screw tightens (Figure 2).
6. Tighten screws on terminal posts. Pull cord until slack is out. Lay
aside until ready to attach to lamp.
[Illustration: Figure 2 (Attaching Cord to Plug)]
7. Remove lamp shade, shade-holder, bulb, and diffusing bowl, if there
is one.
8. Separate the metal shell of socket from its cap by pressing on shell
at place marked "press," and pull socket from cap.
9. Pull on socket body to get some slack in lamp cord. Loosen screws and
detach cord. Pull cord out through base of lamp. You can splice new cord
to the old one and use the latter to "string" the new wire.
10. Pass the new cord up through the lamp base and socket cap, tie a
simple half-hitch knot in the cord to prevent strain on the terminals,
and attach wires to the terminals on the socket (Figure 3). If there is
likely to be any strain on cord, use an Underwriters' knot. Twist
strands and attach wire in direction in which screw tightens.
11. Pull slack out of cord in lamp so that socket rests in socket cap,
replace shell and reconnect cap. Be sure the fiber insulator is in the
shell. You'll feel or hear a click when the notches in shell are locked
to the projections in the cap.
12. Replace bulb, inspect carefully, and test. (In floor lamps where the
cord runs through the center post and out under the base, the cord will
last longer if it is fastened with tape so it doesn't rub edge of lamp
base when lamp is moved.)
13. If the lamp has a porcelain socket, simply disconnect the wires at
the terminals, remove the old wire and connect the new one.
[Illustration: Figure 3 (Socket and Switch Assembly)]
What Did You Learn?
Underline correct answers then discuss in the group. (There may be more
than one correct answer.)
1. The part of the lamp that usually wears out first is (the socket)
(the cord) (the plug).
2. Lamps that waste electricity are those which have (bad wiring)
(frayed cords) (dirty shades or bulb).
3. To unplug a lamp you should grasp (cord) (plug) firmly and pull.
4. Wire in lamp cord usually comes in sizes 16 or 18. Size 16 is the
smaller (true) (false).
5. In fastening wire around a terminal post it should go around in a
(clockwise) (counter-clockwise) direction.
6. When the switch on a lamp is turned off, the electricity only goes as
far as (the wall plug) (the switch).
7. An Underwriters' knot should be used (only when there is room for it
in the plug) (whenever there is likely to be strain on the cord, even if
you have to replace the plug with a larger one).
SUGGESTED DEMONSTRATIONS
Show how to inspect a lamp and its cord. You might tie tags on the cord
and lamp at points of danger or failure--at the plug, wear points next
to lamp base, bad sockets.
Demonstrate the process of repairing a lamp cord, socket and plug.
Make a board display of the parts of the lamp socket showing cord
attached.
Make a display of the types of lamp cords and plugs in common use.
Using two lamps, one with clean bulb and shade, the other dusty, show
how the former gives more light.
For More Information
Lamps have an interesting history. Look it up in your local library. Ask
someone from your power supplier or electric dealer to talk to the club
about the different kinds of lamps. Your leader has or can get
additional information on lamps, if you wish.
[Illustration]
What Did You Exhibit
What Did You Demonstrate
LESSON NO. B-4
Credit Points 3
MAKE A TROUBLE LIGHT.
A handy piece of equipment in the home and on the farm is a heavy-duty
extension cord with a shielded light and a side outlet on it. When you
want to work on the car or tractor in the yard at night, the trouble
light is better than a flashlight. You can use it both for light and as
an extension cord. It is safer than matches or a lantern, especially
around the garage or barn.
It is easy to make a trouble light, and it gives you good practice in
electrical work. Of course you can buy one, but you wouldn't have the
fun of making it nor would it suit your needs. Trouble lights are not
for permanent use--they're for emergency use and to provide light or
electricity in places where they are seldom needed. When you find a
trouble light being used as permanent wiring, that's the place to
install an outlet.
What Size Cord?
Choose the right kind of cord. What length will be best for your various
uses? A cord too long may be bothersome to use and store. What will be
the heaviest load you are likely to put on the cord, in amperes? Check
appliances you may want to connect to it. No. 16 wire can carry 10
amperes safely for a distance of 50 feet, while No. 18 can carry only up
to 7 amperes for a distance of 40 feet. You'll want a "hard service"
cord, called S, ST, or SO-type cord by electricians. Junior hard service
cords, known as SJ, SJT, or SJO, are fine for lighter duty.
Cord, Plug and Guard
A rubber-handled socket should be used for safety and to withstand hard
knocks. It should have a switch on it, preferably a push switch in a
recess in the handle.
The connector or attachment plug should be of rubber or solid plastic
and have a metal cord grip fastened to it. This grip will hold the cord
firmly and prevent strain on the terminal connections.
[Illustration: Finished Trouble Light]
Get a good lamp guard. If the wire is too light, it may bend and break
the bulb when hit or dropped. For the lamp itself, get a rough service
lamp. An ordinary lamp won't last long with rough usage.
How to Make the Trouble Light
_Tools Needed:_
Your 4-H electrician's kit or screwdriver, knife and soldering iron
_Materials Needed:_
1. About 20 feet of 2-wire, No. 16 heavy duty (hard service)
2. A rubber-handled socket with switch and a side outlet
3. A shielded lamp guard
[Illustration: Materials Needed]
4. A good connector plug cap, preferably with a clamp-type grip for the
cord
5. A rough service lamp bulb
6. Solder and flux
_Steps to Take:_
1. Remove about 2 inches of the outer covering of cord at one end.
2. Separate the wires and cut away the filler material.
3. Remove 3/4 inch of the conductor insulation from the end of each wire
and tightly twist the strands together to form a firm conductor. Be
careful not to cut any of the fine wires. Ends may be soldered.
4. Slide the plug in position on the cord.
5. If there is no cord grip, tie the underwriters' knot (Figure 1). If
there isn't room enough, make an "S" loop by passing the wires around
the prongs before fastening them to the terminal screws as explained in
the next step.
6. Loop the bare part of the wire around the screw in the direction the
screw is turned to tighten (clockwise direction). This will prevent the
wires from being forced out from under the head of the screw as it is
tightened. Now repeat with the second wire, wrapping it around the other
prong of the plug.
_Connecting the socket._
1. Separate the parts of rubber-handled socket (Figure 2).
2. Prepare the other end of the cord as in steps 1, 2, and 3 above.
3. Insert the cord through the rubber handle and socket guard.
4. Tie the holding knot (underwriters' knot) as explained in Step 5.
5. Connect wires to terminal screws and assemble the rubber-handled
socket.
6. Screw in the rough service lamp and test your cord.
7. Put the shielded lamp guard on the socket and tighten the holding
clamp until it is firmly in place. You are now ready to use or
demonstrate your trouble light.
8. After you've made your trouble light, decide on a good place to keep
it where it will be handy for use. Loop it carefully and hang it over a
wooden dowel rather than a nail. It will last longer.
[Illustration: Figure 1 Tying an Underwriter's Knot]
[Illustration: Figure 2 Disassembled Light]
What Did You Learn?
(Underline correct answer)
1. A Junior Hard Service Cord is known as an (SO-Type) (SJO-Type) cord.
2. You disconnect a cord by (jerking it from the socket) (grasping plug
and pulling it out).
3. Brass sockets are unsafe because (they break too easily) (the exposed
metal can cause short circuits).
4. Rubber-covered cord is safer for emergency cords than fabric because
(it will stretch) (it will insulate and protect the wires inside).
5. In a trouble light (any kind of bulb will do) (a rough service bulb
is best).
Ideas for Demonstrations and Exhibits
1. Show how to make your trouble light and a method of storing it.
2. Show a safe trouble light, and an unsafe trouble light with danger
points marked.
3. Show cutaway pieces of different types of cord.
For More Information
Ask your power supplier, county highway engineer, police official or
leader to tell you about various types of portable emergency lights and
their uses.
LESSON NO. B-5
Credit Points 5
WHAT MAKES MOTORS RUN
What makes an electric motor run? Can you make an electric motor that
will run? Certainly you can, and by doing so you'll learn why it runs.
It won't be mysterious any more and you'll be ahead of all the millions
of people who use motors every day and never know why or how the motor
converts electrical energy into useful power.
[Illustration]
Motors Are Magnets
You know how one end of a compass needle always points to North. No
matter how you turn the compass, the same end of the needle always
swings to the North. The earth itself and that small compass are both
magnets (Figure 1). Each has a North pole and a South pole. Around the
poles of each there are magnetic fields, invisible lines of force that
attract and repel.
[Illustration: Figure 1. The same end of the compass needle always
points to the earth's magnetic North Pole.]
The N poles _repel_ each other and so do the S poles. The N and S poles
_attract_ each other. In other words, opposite poles attract; poles that
are alike repel each other.
Lay 2 bar magnets on a table side-by-side. If both N poles are at one
end, they'll repel each other and almost flip around until there's a N
pole lying next to a S pole (Figure 2).
[Illustration: Figure 2. Small bar magnets laid side by side move so
that the North pole of one is near the South pole of the other.]
Now suppose we place one of the bar magnets on the table. The other,
we'll fix on a pivot so it can spin around. This one we'll move so its N
pole almost touches the fixed magnet's N pole. As soon as we release it,
the movable magnet will spin around so its S pole will be near the N
pole of the stationary magnet. That's an electric motor--almost.
[Illustration: Figure 3. A movable bar magnet pivots so its South pole
is near the North pole of a stationary magnet.]
It's not quite a motor because the rotating magnet will just move as far
as it has to in order to get the opposite poles together. You might be
able to cause the movable bar magnet to make turn after turn. You could
do this by turning the fixed magnet quickly end for end. This wouldn't
be very practical as a motor.
We Can Improve It
If we could change the pole on one end of the rotating magnet just as
soon as it reaches the attracting pole, it could make a complete circle.
In doing that, the pole at the near end of the rotating magnet would be
repelled by the stationary magnet and pushed away. As soon as the
opposite end of the rotating magnet would come into the magnetic field,
it would be drawn to the stationary magnet. In order to keep the "motor"
running, we would have to constantly change the poles at each end on
every half revolution.
We Need An Electromagnet
We can't reverse the poles on simple bar magnets, but we can on
_electromagnets_. We can make one by wrapping a wire several times
around an iron core to form a coil. This magnet will also have a N and a
S pole when connected to electrical current. The big difference is that
the poles can be changed instantly by reversing the current in the wire.
Switching Poles Automatically
The rotating electromagnet will have to be connected to the 2 wires
through which we pass the current. Since it's rotating on a center
shaft, we can't have a solid connection. Instead we have to extend the
wires from the coil out along the shaft and let the electric contact be
made with brushes which touch the wires along the shaft.
[Illustration: Figure 4. A rotating electromagnet changes poles as
contacts are made first one way, then the other.]
This is a simple way to reverse the current in the coil of the
electromagnet.
Increasing Efficiency
Instead of using only one pole of a stationary magnet, we can use both.
This is done by shaping the stationary magnet around the path of the
rotating electromagnet. This way we have the benefit of the attracting
and repelling forces from both poles. The effect is doubled.
We can also wrap wires around this circular iron and make an
electromagnet of it. But when we wire this magnet we use no brushes
because we want the current to flow in one direction only.
The stationary electromagnet is called the _field_. The rotating
electromagnet is the _armature_.
WHAT TO DO: Make A Motor
_Tools Needed:_
Pocket knife, hammer, vise (or 2 pairs of pliers).
_Materials Needed_:
1 roll of No. 24 enameled wire
1 roll of electrician's tape
3 - 4" (20-penny) nails
4 - 2-1/2" (8-penny) nails
4 - 3" brads (10 penny)
Wood board for motor base
2 staples or 4 small brads
2 tacks
2 - 3 volt dry cell batteries (or a 6
volt transformer).
Step No. 1-Armature
Wrap about 1-1/2" of a 4" nail with two layers of tape. This will be the
shaft.
The iron core will be made of two pairs of 2-1/2" nails. Wrap tape
around each pair with heads and points alternated.
Center both pairs on each side of the shaft. Place them about 1" from
the head of the shaft nail. Wrap them together with two layers of tape
from tip to tip.
Start at the shaft and wind No. 24 enameled wire to one end and back.
Then do the same on the other end. Always wind in the same direction.
Leave 6" of spare wire at start and finish.
Step No. 2-Commutator
Scrape all insulation off the ends of the wire. Bend the bare ends back
and forth as shown. Lay them flat over the taped shaft-one on each side
of the shaft.
Hold the commutator down with narrow strips of tape. Wrap tightly near
the core and at the opposite end.
Step No. 3-Field
Make the core by bending two 4" nails in the middle at right angles.
Space the heads about 3" apart to form a horseshoe. Wrap together with
two layers of tape.
Wind about 400 turns of wire around the center. Leave 4" of spare wire
at start and finish. Attach to wood base with staples at each end of
the wire. Small brads, bent over, will do just as well.
Step No. 4--Armature Supports and Brushes
Scrape the insulation from the ends of two 6" pieces of wire. Tack
them to the base and bend them as shown to make brushes.
Drive two pairs of 3" brads into the base about 3-1/4" apart and in a
line midway between the field poles. Wrap wire around the supports to
form armature bearings.
Scrape insulation off ends of wire from the field. Connect one end to
a brush wire.
_Assemble As Shown_
Adjust the position of commutator and tension of brushes against it for
best operation.
Take the armature off the motor and connect the commutator wires to a
dry cell battery. Test the polarity of each end of the armature with a
compass. Switch the connections on the commutator and test again. See
how the compass needle changes direction?
With the armature still off, connect the field coil directly to the dry
cell. Test the polarity of each end of the field with the compass. How
can you reverse the polarity? Try it. It's easy.
Reassemble the motor again and start it. Push the field poles slightly
out of alignment with the turning armature. What happens to the motor's
speed? Can you tell why?
This time, push the field poles completely out of the way. Test the
polarity of the armature as you slowly turn it by hand. Do you see what
happens and why it does?
Try to reverse the direction of rotation of your motor by reversing the
connections at the battery. What happens? Can you explain why?
Demonstrations You Can Give
Make a display board showing the parts of the toy motor and explain how
each part works compared with the parts of a commercial motor.
For Further Information
There are several other types of toy motors you can build. Your club
leader or power supplier can help you find information about them.
1. Did your toy motor run?
2. Did your motor speed up or slow down when you pushed the field poles
out of line? Why?
3. What happens to the magnetic polarity of the armature when you turn
it slowly by hand and check it with a compass?
4. How can you reverse the direction of rotation of your toy motor?
Is there another way too?
What is it?
LESSON NO. B-6
Credit Points 3
TAKING CARE OF ELECTRIC MOTORS
Through the magic of electric motors, much of our work is done faster
and better at lower cost than we could do it without the help of the
electric motor. People who use motors and treat them properly have much
more time for other work and for leisure time activities. A
1/4-horsepower motor running quietly and steadily hour after hour will
do the work of one man, and operate all day for about 5 cents without
tiring. On many jobs it will work without "supervision", turning on and
off automatically, as required. It does this on water pumps, in heating
and cooling units, and on fans and similar appliances.
All that a motor needs to do its work is electricity and a little care.
Let's see what you can do to give proper care to motors in your home and
on your farm.
You'll Need
A light oil (SAE 10) for motors of less than one horsepower and a
slightly heavier oil (SAE 20) for larger motors. See if you need grease
for cups which may be on large motors. If so, be sure you use
ball-bearing grease and not ordinary cup grease. Cotton waste or clean
rags will be needed for wiping off the motors, and a tire pump or vacuum
cleaner for blowing out the dust or dirt.
[Illustration: Some motors have instructions for oiling on the
name-plate.]
WHAT TO DO
1. First, make a list of all the electric motors that work for your
home. You may wish to make a separate list for your farm buildings.
You'll probably be surprised at how many there are. Don't forget the
sewing machine, the refrigerator, the freezer, the vacuum cleaner and
other small but important motors. Don't touch any motor that is running.
Disconnect them before you touch them.
2. Make a motor service chart with columns headed: Use, Location,
Horsepower, Volts, Amperes, Service Required, Date Serviced and What was
Done. (See sample) Then list all the motors that require any servicing.
Some will have the instructions on the motor or appliance; the
instruction booklet that came with the motor or appliance will also tell
what servicing is required.
_Step 1._ Plan the job. Start with the motors in the home. Then you can
care for the motors on the farm.
_Step 2._ Be sure that any motor on which you are going to work is
disconnected. Then wipe the outside case clean with a cloth. If the
motor has openings in the end, use a vacuum cleaner to suck out dust,
dirt or chaff. A tire pump may also be used to blow out this dirt. If
you use compressed air, be sure the pressure is not high as it may
damage wiring inside the motor. Dust-proof motors should be used in
dusty or dirty places.
_Step 3._
[Illustration: If there are oil holes, oil according to the
manufacturer's instructions.]
If there are no instructions, remember a little oil goes a long way as
far as motors are concerned. Motors of less than one horsepower require
only 3 or 4 drops (not squirts) of oil every 3 or 4 months if the motor
is used frequently. Too much oil can damage the motor. It spoils the
insulation.
If there are no oil holes or grease cups on the motor, it is probably
lubricated by means of grease sealed in the bearings at the factory, or
it may use greaseless bearings, and does not need to be oiled or greased
periodically. Indicate on your chart all motors which need periodic care
and see that it is given according to schedule.
Wipe away any excess oil or grease. Be sure oil holes are capped or
covered.
_Step 4._ Reconnect motor and run for a moment.
_Step 5._ Record on the chart the date you serviced the motor and what
was done.
What Did You Learn?
How many motors are there in your home? ______ On the farm? ______
How many motors need regular oiling or grease? ______
How many are less than one-horsepower? ______
SAE Oil ______ is used to oil motors up to 1/2 horsepower. How much
oil?______
SAE Oil______ is used for larger motors.
Demonstrations You Can Give
1. Show how to clean a small motor.
2. Explain proper lubrication of motors.
3. Using the chart prepared in this work sheet, give a talk about the
motors that work for you-the job each one does, which ones need oil or
grease, which need no attention, and why, etc.
4. Use a homemade toy motor to explain "what makes motors run."
5. Show proper way to replace worn cord on a small motor.
For Further Information
Ask your county Extension agent or 4-H leader for more literature on
motors. They can help you obtain a film or a speaker such as a power
supplier, a local electric dealer, or electrical contractor to discuss
motors.
Also visit your public library and see a science teacher for more
information on motors.
ELECTRIC MOTORS SERVICE CHART Sample
Use a table like the following to list the motors around your farm and
home.
----------------------------------------------------------------------
Motor | Location |H.P.|Volt |Amp |Service |Date Serviced and
Use | | | | |Needed |what was done
----------------------------------------------------------------------
Food | Kitchen |1/6 |120 |4.4 |Clean & Oil; |9/1-Cleaned
Mixer | | | | |cord needs |w/cloth.
Repair | | | | |repair |Oiled w/#10 Oil;
| | | | | |repaired cord
----------------------------------------------------------------------
Tool | Farm |1/4 |120 |5.8 |Clear, oiling; |10/6-Cleaned
Grinder | Shop | | | |Have switch |w/vacuum Oiled #10
| | | | |Have switch |oil. 10/20-Had
| | | | |repaired |switch repaired
----------------------------------------------------------------------
Pump |Pump |1/3 |120 |7.2 |Oiling, |9/26-Cleaned
|house | | | |cleaning |w/tire pump;
| | | | | |oiled w/10 oil
----------------------------------------------------------------------
LESSON NO. B-7
Credit Points 4
READING THE ELECTRIC METER
There is no question but what electricity is one of the lowest cost
services in the home and on the farm. A few pennies worth of electricity
will provide the power to run machines that take the place of a man or
of several men working all day. However, we all like to know what things
cost.