Part 5

_First_, make popcorn the way you usually do. Set a front surface unit control on the range at "medium high". Pour enough oil to very lightly cover the bottom of the pan. When the pan is hot, pour in enough popcorn to cover the bottom with one layer of kernels. Use the potholder in one hand to hold the cover on, and with the other move the pan back and forth across the unit. When the popping stops, remove from the heat.

How did the heat get to the popcorn?

_Second_, make popcorn in the oven. Add the oil to the pan, cover it and put it in the oven. Turn the oven on, with the automatic control set at 400°. When the oven indicator light goes off, this means that the proper temperature has been reached. With the potholder, remove the pan and add one layer of popcorn kernels. Replace the pan in the oven. When the popping stops (listen for it) remove the pan.

What kind of heating took place here?

_Third_, make popcorn with the heat lamps. Clamp the lampholders to the back of a chair or other vertical support. They should be 6 to 8 inches apart and pointed directly at each other. Put about 2 tablespoonfuls of popcorn in the Wire basket or strainer. Do not add oil. Hold the basket midway between the two lamps. When the popping stops, turn off the lamps.

What kind of heating was this?

Now, butter and salt the popcorn you have made and share it with others.

What Did You Learn?

1. How is heat transferred from one body to another?

2. Could chicks or pigs receive warmth from a heat lamp without the air in the pens becoming warm? Explain.

3. How does a broiler unit in a range cook meat?

4. How does an oven bake food?

5. Tell why iron picture wire was used instead of copper wire for your heating demonstration.

LESSON NO. B-13

Credit Points 2

MYSTERIOUS MAGNETISM

In ancient times, people found certain rocks that clung together in bunches. These rocks were very mysterious. People didn't understand them and many superstitions grew up about lodestones, as these rocks were called. Lodestone (sometimes spelled loadstone) means leading stone. People even told Columbus not to sail out of sight of land because a giant lodestone was just over the horizon waiting to pull all the nails out of his ships.

The Chinese were the first to use magnets. They found that if you hung a lodestone by a string, one end of the stone would always point in the direction of the North Star. They had the first magnetic compasses.

An artificial magnet can be made by stroking or gently rubbing a piece of steel with a lodestone. This piece of steel then can be used to magnetize another piece of steel. This can be continued on and on. Lodestones are not always available but you can get the same results with an electric current. So, magnetism and electricity are very closely related.

What to Do

Learn about magnetism by doing the experiments that follow.

Seeing is believing!

Materials You Will Need

2 dry cell batteries (#905) A few feet of No. 18 bell wire 3 steel knitting needles or similar hard steel 2 ft. of light thread Sheet of light cardboard or stiff paper Permanent magnet (bar or horseshoe) Compass 1 or more large nails or spikes Red and black china-marking pencils or crayons

Iron filings Wire cutters Carpet tacks

(Iron filings usually can be found under the grinding wheel in a shop. If you can't find any, rub some steel wool pads together to produce bits of metal that will do.)

"See" a Magnetic Field

Cover the permanent magnet with the cardboard or paper. Sprinkle iron filings on the paper. Tap the paper and note the pattern formed. Strings or lines of filings pass from one pole of the magnet to the other. The area covered by the filings is the center of the magnetic field. To remember this, you might compare the magnetic lines of force that arrange the iron filings to the contour strips in a farmer's field.

This magnetic field is one of the important things in our everyday life with electricity. If it were not for the magnetic field, we would not have electric motors. Telephones, radios, television, and many other things we use every day also depend on this magnetic field.

Make an Electro-Magnet

You can make magnetism work for you by winding several turns of insulated wire around one or more large nails or spikes (soft iron). Connect one end of the wire to the battery. Touch the other end of the wire to the other terminal for a few seconds and see how many tacks you can pick up. Repeat the experiment using as many turns as possible. How many more tacks were you able to pick up?

You have made what we call an electromagnet. When you disconnect the wire, the nails fall off. This is one of the advantages of an electromagnet. We can turn magnetism on and off as we wish. Picture a crane operator throwing the switch and picking up scrap iron and steel. Then he opens the switch to drop the scrap metals.

Soft iron can be magnetized easily as you have just seen, but loses its magnetism in a short time. Steel is harder to magnetize but holds its magnetism almost indefinitely.

Make a Permanent Magnet

Wrap the insulated bell wire around the steel knitting needle. The wire should be wrapped the full length of the needle. One end of the wire is connected to the battery. The other end of the wire is then touched for just a few seconds to the other terminal. This should make the needle into a permanent bar magnet. If you did not get results, try two batteries in series, wind more turns of wire on the needle, and leave it connected a little longer. Do the same thing with the second knitting needle. In the same way, you can magnetize a screwdriver, so that you can use it to pick up and hold steel screws. Don't do it unless you want your screwdriver to be magnetized.

See How They Attract and Repel

Take one of the magnetized needles and hang it with a thread. A thread stirrup (Figure 4) will help keep it level. Be sure it is not near other large pieces of steel. Watch the needle. Does it settle down, pointing in one direction? (Check to see if this is the same direction as your compass). If it does, you have made a compass. The tip of the needle pointing north is called the North Pole (North-seeking pole). The other end is called the South Pole. Mark the North Pole with a stroke of the red marking pencil. Mark the South Pole black. Do the same thing with the second needle. You can show this with a sewing needle, and a notched cork, and a bowl of water. Rest the needle in the notched cork, and float it on the water.

Hold the compass near the North Pole of the needle. What happens? Does the South Pole of the needle attract the North or South Pole of the compass? Try this with the second magnetized needle. See if you can prove the rule that like poles repel (drive away) and unlike poles attract.

Connect one end of a wire loop to the battery and run the wire directly over the compass. Touch the other end of the wire to the battery. Which way does the compass point now? If you get some motion out of the compass needle, this proves there is a magnetic field around the wire when current is flowing. This relation between electricity and magnetism is the thing that makes electric motors and generators work.

Make Many From One

Lay the third needle (unmagnetized) on a table and stroke it with one of the magnetized needles. (See diagram) Always stroke it in the same direction. Raise the magnetized needle at least two inches on each return stroke. Thus you can magnetize the needle by using the other needle.

Use the wire cutters to cut the first magnetized needle in short lengths. (Cover the needle with a cloth to keep the pieces from flying.) Can you show by using the compass that each piece is a complete magnet? Hold one end, then the other, of each piece to a compass. Does each piece have both a North Pole and a South Pole?

Magnetism and Animals

The things you have done show that electricity and magnetism are related in many ways. Magnetism is mysterious, and there are still things to discover about it. It is thought that animals and birds are aided in their sense of direction by magnetism. It is commonly known that when a person gets lost in the woods, he tends to go around in circles. Possibly this is caused by the earth's magnetic field.

What Did You Learn?

1. Where are natural magnets obtained?

2. How can artificial magnets be made?

3. What material is needed for a permanent magnet? For a temporary magnet?

4. How can you find out which is the North Pole of an unmarked magnet?

5. How many poles does a magnet have?

6. Which magnetic poles attract each other?

7. Why couldn't you make a compass out of a strip of plastic?

8. What causes the compass to change direction when a wire carrying battery current is held over the needle?

9. List the materials you would need and tell how you would build a homemade compass.

10. Tell what you enjoyed most about becoming acquainted with mysterious magnetism.

LESSON NO. B-14

Credit Points 2

Give your appliances and lights a square meal

Would you say that having enough to eat was pretty important in the home that you know?

The "food" for your appliances and lights is electricity, and like you they must be "fed" enough.

What to Do

1. List the appliances and lights in your home.

2. See if any of them are "starving" for the electricity they need.

3. Learn how the electricity gets to where it's used.

4. Make a chart of the electrical circuits in your home.

5. Make sure that each circuit is protected with the right fuse or circuit breaker.

Count Your Electrical Blessings

Many people in much of the rest of the world wish that they could trade places with us, because we have so many electrical appliances in our homes.

Of course, we have not always had as many appliances as there are today. When electricity first came along, people used it only for lights. Then, they began to add flatirons, washing machines, refrigerators, coffee percolators, and radios.

Then more and more electrical things were made for people to use and enjoy. Now we have dozens and dozens of uses for electricity in our homes.

How many different uses for electricity are there in your home today? Ask your parents how many there were when your home was built or first wired. How many were _common_ when your parents began to keep house?

Some Homes Are Behind Times

Many older homes were built before electricity was available, and were wired later. And like them, some older homes that were wired as they were built had only enough wiring for lights and a few other appliances, because those were the only uses that were known at that time.

But people kept on living in these homes, and kept adding to the uses they made of electricity without adding to their wiring.

What has this meant? Well, if electricity were like cars and trucks, you could say that some people are trying to put turnpike traffic through a back-country dirt road!

Watch for Signs of Starvation

Of course, as your state has done with its highways, some people have expanded and modernized their wiring. But many others have not yet seen this need, or if they have, they may have to do it again.

Here's why:

Your power supplier delivers current to you at the right voltage or electrical pressure. If the wires in your house are large enough, they will pass this full voltage on to the appliances.

But if your wiring is too small, the electricity arrives at the appliances so weak that they can't work properly, and much of what you pay for is wasted.

Here are some things you can watch for in your own home. They will tell you whether your appliances are getting enough electrical "food" or not.

1. _A shrinking TV picture_--If it draws in from the sides of the screen, fades, loses contrast, or if the sound becomes distorted, you may have low voltage.

2. _Too much fuse blowing or circuit breaker tripping._

3. _Heating appliances are slow to do their jobs._

4. _Lights dimming_, when motors or other appliances are turned on.

There Should Be Enough Ways to Get "Appliance-Food" Around

If appliances in your home show these starvation signs, then you may not have enough ways for the electricity to get to where it's used.

There are three kinds of these electrical highways or circuits, and your home should have enough of each:

1. _General purpose circuits_--These serve lights all over the house, and convenience outlets everywhere except in the kitchen, laundry, and dining areas.

A rule-of-thumb is: There should be at least one general purpose circuit for each 500 sq. ft. of floor space.

2. _Small appliance circuits_--These are not used for lights, but instead they supply convenience outlets in the kitchen, laundry, and dining areas where portable appliances are most used.

Every home should have at least two small-appliance circuits.

3. _Individual or special-purpose circuits_--One of these is needed for each: electric range, dishwasher, water heater, freezer, automatic washer, clothes dryer, air conditioner, pump, and house heating equipment.

+----------+------+------+------+------+-------+ | | | | | | | | Actual | | | | | | | Size | | | | | | +----------+------+------+------+------+-------+ | Gauge | | | | | | | Size | 14 | 12 | 10 | 8 | 6 | +----------+------+------+------+------+-------+ | Fuse or | | | | | | | Breaker | 15 | 20 | 30 | 40 | 55 | +----------+------+------+------+------+-------+ |Max. Watts| | | | | | |at 115 V. | 1725 | 2300 | 3450 | 4600 | 6325 | +----------+------+------+------+------+-------+ |Max. Watts| | | | | | |at 230 V. | 3450 | 4600 | 6900 | 9200 | 12750 | +----------+------+------+------+------+-------+

Each Circuit Big Enough

The capacity of each circuit is limited by the size of its wires. The chart above shows you the actual sizes of wires commonly used in permanent home wiring, and what each will carry. Notice that each size is given a number, and the smaller the number, the bigger the wire.

Also notice that a given size of wire will carry twice as many watts at 230 volts as it will at 115 volts. (Watts are figured by multiplying amps times volts.)

General purpose circuits usually are either Number 14 or Number 12 wire, at 115 volts. What is the capacity of each, in watts? (Number 12 wire is recommended for all new general purpose circuits.)

Small appliance circuits are required to be at least Number 12 wire.

Individual circuits are always sized according to the appliance they serve. Find the size wire that should be used for a 10, 000-watt, 230-volt range; a 1500-watt, 115-volt dishwasher; a 4500-watt, 230-volt clothes dryer. ________ ________ ________

Only One Fuse Size Right

A fuse in an electrical circuit is like an alert traffic policeman--stopping everything if there's danger. A circuit breaker serves the same purpose, and the right size is installed when the wiring is done.

A policeman uses his brain to tell him when to blow his whistle, but a fuse depends on the size of the little fusible (meltable) metal link that you see under the glass.

If too great an electrical load is added to a circuit, this link will melt and prevent a dangerous overload. If you put in a fuse with too heavy a link, it will not melt in time, and the wiring and equipment may be damaged.

Therefore the right size of fuse is very important, and is something that you should check in your own home.

See the chart above for the right fuse for each size wire.

Make a Circuit Chart

At one or more places in your home there is a box or panel containing the fuses or breakers for the various circuits. Attached to the inside of the door of each such panel should be a chart something like this:

+-----+---------------------+-----------+ | No. | Description | Fuse size | +-----+---------------------+-----------+ | 1 | Range | 40 | +-----+---------------------+-----------+ | 2 | Kitchen Outlets | 20 | +-----+---------------------+-----------+ | 3 | Dining Room Outlets | 20 | +-----+---------------------+-----------+ | 4 | Living Room Outlets | 15 | +-----+---------------------+-----------+ | | | | +-----+---------------------+-----------+ | | | | +-----+---------------------+-----------+

Notice that in our chart we have made columns for a description of what each circuit serves, its number or position in the panel, and the proper size fuse for it.

Because most such charts leave out this last very important bit of information, you should make a complete new chart, like the one shown. Provide as many lines as there are fuse positions. Paste or tape it to the inside of the panel door.

Then, ask permission of your parents to disconnect all the circuits by unscrewing the fuses or flipping the circuit breakers. _Do not touch anything but the fuse rim._ Then reconnect them, one at a time, to find out what each circuit serves. Turn on as many lights as you can, to help you in your detective work. Use a test lamp at those outlets that do not have a light connected to them. Write two or three words describing each circuit on the proper line on your chart.

On a separate sheet, keep track of the appliances and lights that are on each circuit, and add up the watts. (If the name-plate of any appliance gives "amperes", "amps", or "A" instead of watts, just remember that amps times volts equals watts.) This will tell you if any of them are overloaded. Show this sheet to your parents.

Check the Wire Sizes

_Disconnect the main switch_, and determine the size of the wires in each circuit. Don't include the insulation in your measurement.

_BE CAREFUL!

Even though you have disconnected the main switch, the wires coming into it are still "live". So, do not touch any wires. Instead hold the wire size chart near them so that you can tell which gauge each one is._

Write in the proper size fuse for each circuit on your chart.

Replace Any Wrong-Size Fuses

Do the fuse sizes you have written on your chart agree with the ones that are in place in the panel?

Get the right size fuses and replace any that are wrong. Make sure that you have a reserve supply of the right sizes, and that they are handy for future use.

Talk it Over With Your Parents

Do you think that your home has enough of the proper size circuits? If not, talk it over with your parents. They may want to ask an electrician to go over the wiring and make the necessary changes.

What Did You Learn?

(Underline the right answer.)

1. A (television set, radio) is very sensitive to changes in voltage.

2. Dimming lights mean (static in the wires, an electrical overload).

3. Wires that become warm from overload make it (more expensive, cheaper) to operate the equipment.

4. A home of 2,000 sq. ft. should have at least (three, four) general purpose circuits.

5. One solution to low voltage symptoms is (heavier fuses, more circuits).

6. Full capacity for a Number 14 wire circuit at 115 volts is (1725 watts, 3000 watts).

7. A room air conditioner should be on (a general purpose, an individual) circuit.

8. The purpose of a fuse is to (let you disconnect the circuit, automatically prevent overloading the circuit).

9. The right size fuse is determined by (wire size, the store where you buy it).

10. A circuit chart should give (circuit description and fuse size, the maker's name).

Demonstrations You Can Give

Ask your leader to help you plan a demonstration. You can show how lights dim when too many other appliances are connected, how a fuse protects against overloading, and the danger of using too large a fuse.

For More Information

Ask your Extension agent, power supplier, or electrician for additional help.

LESSON NO. B-15

Credit Points 4

YOU CAN MEASURE ELECTRICITY

Instruments that can detect or measure the flow of electricity have helped to make possible the wonders of electricity as we know them today.

Scientists in laboratories must have measuring devices for experiments leading to new uses of electricity. Power suppliers must have instruments that tell what the generating equipment is doing and to measure the amount of electricity being sold to users. Factories need instruments that keep tab on electrical equipment to make sure electricity is being used efficiently.

In fact, almost anywhere you find electric power at work you'll find electrical instruments--even in your home. The one you know best measures the amount of electricity used. Another, in the family car, shows whether the generator is charging the battery or if the battery is discharging.

What to Do

1. Make a simple kind of direct-current meter that will show you that there's a magnetic field around a wire carrying an electric current and that will detect a very tiny current.

2. Make a more refined D.C. instrument (galvanoscope) and measure the voltage of different sizes of dry batteries, and show how an electric current can be induced.

Tools and Materials You'll Need:

Pair of pliers, knife, small hammer 30 feet of No. 24 bell or magnet wire Compass Two coins--a penny and a dime Fine sandpaper Blotting paper Plastic or cellophane tape Wooden blocks (See Figure 4) Glue 2 small nails One #905 dry cell, a penlight battery, and two regular flashlight batteries Table salt Drinking glass 2 paper clips Two machine bolts

How They Work

Like many electrical things, most electrical instruments depend on the action of magnetism created by an electric current. There is a magnetic _field_ or lines of force around any wire carrying an electric current. If this field is controlled and made to react on a sensitive device, like an easily moved pointer, we have an electrical instrument.

Detect a Magnetic Field

First, let's prove that there is a magnetic field around any wire carrying an electric current. Take a piece of wire about two feet long and scrape off about an inch of insulation from each end. Connect one end to a battery terminal. Make a loop of wire that crosses the face of your compass, north to south. Now touch the other end of the wire to the other battery terminal.

(DO NOT attempt to substitute alternating current, as from a model railroad transformer because its alternating current will cause the compass needle to swing rapidly from one side to the other.)

What happens? Your compass needle should move to one side because it is very sensitive to magnetic influences. This proved that the wire created a magnetic field or lines of force when we passed electricity through it. (Figure 1)

Detect a Tiny Current

How sensitive is your simple electric meter? Take about five feet of wire and wrap it around your compass as in Figure 2, keeping the turns bunched together as much as you can. Leave about six inches at both ends of the wire extended for leads. Scrape the insulation off the last inch of both. Rotate the coil and compass until the needle and coil are parallel, both pointing north and south.