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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

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.

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.

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 Three 3-penny box nails Two small screws or carpet tacks Two 2-inch rubber bands Two miniature sockets with solder terminals Two l-l/2-volt flashlight bulbs

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.

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 . 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.

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 . 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.

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?

LESSON NO. B-2

Credit Points 4

TOOLS FOR ELECTRICIANS

Who goeth a borrowing Goeth a sorrowing Few lend 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

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