and magnetism are vital to our modern world. Without
would still be warming ourselves with open fires and would
the many electrical and electronic devices we take for
day. Imagine a world without television, electric
computers, or air conditioning. Yet without an understanding
electricity and magnetism, none of these inventions would
been possible. On the Electricity and Magnetism pages,
will follow in the
of many scientists as we explore these two fascinating
first type of electricity to be discovered was static
electricity. The discovery of static electricity was
first step toward learning about electricity.
Many years ago, it was found that certain objects were given an electric charge simply by rubbing them with certain other objects. These objects, when charged, would then attract other objects. This charge came to be known as “static electricity”. This first series of experiments illustrate some of the properties of static electricity. They are best done on a cool dry day, but in summertime, they will often work in an air-conditioned room as well.
Ever have a bad hair
day? Try this, and the day won’t be a total loss!
Materials Needed: Plastic comb; paper.
Procedure: Tear off several bits of paper about the size of a pea or smaller and place them on a table or counter. Bring the comb near to the paper bits. What happens?
Next, run the comb through your hair several times and again bring the comb near the bits of paper. What happens now?
What Happened: The first time you brought the comb near the paper bits, nothing happened, but when you combed your hair, you gave the comb a charge of static electricity Then, when you brought the comb near the paper bits, they were attracted to the comb because of this charge. We’ll see what caused the attraction a little later.
may have noticed a crackling sound when you pulled off a
sweater on a
cold day. This is another example of static
works best on a dry day in winter.
Materials Needed: Sweater; dark room or closet; mirror.
Procedure: Pull off your sweater in a dark room or closet while watching in the mirror.
What Happened: If you heard crackling, and if the room or closet was dark enough, you should have seen tiny sparks! As you pulled off your sweater, very tiny particles called “electrons” moved in streams between your sweater and your body. You may have even felt your hair stand on end. Each of these streams of electrons jumping between your body and the sweater were actually miniature sparks of lightening.
You’ve probably done this
experiment many times before without ever intending to!
Materials Needed: A carpeted room on a dry day; a doorknob; yourself.
Procedure: Walk across the carpeted floor. Touch a metal doorknob. What do you see, hear and feel?
What Happened: You probably felt a nice little shock! As you walked across the carpet, you picked up loose electrons. When you brought your hand to the door, those extra electrons “jumped” over to the metal doorknob and a spark was created.
Going Further: Try this in a dark room, and you should have no trouble seeing the spark. Also, try touching another person after walking across the room, but be nice... let them know what you’re going to do first!
Balloon; smooth wall.
Procedure: Blow up the balloon and tie it off. Now rub it several times across your hair and then press it against the wall. What happens?
What Happened: The balloon received a charge of static electricity as it rubbed against your hair. This electric charge caused it to be attracted to the wall.
Going Further: Leave the balloon in place for a while. How long will it stay there if left undisturbed?
far, we have seen static electric charges generated on your
In this experiment, we’ll look at one example of static
generated outside of your body.
Materials Needed: Two books; glass from a picture frame; paper; piece of flannel or silk cloth.
Procedure: Clean the glass with a good glass cleaner and allow it to dry thoroughly. Place the two books down side by side with a gap between them just a little less than the width of the glass. Tear several bits of paper about the size of a pea and place them between the books. Place the glass on the books so that it is centered over the paper bits. Now rub the cloth across the top of the glass. What happens?
What Happened: As you rubbed the glass, it was charged by the cloth. The charged glass then attracted the paper bits, but as each of the paper bits touched the glass, they fell back. This is because the paper had a weak charge that was opposite of the glass. Since opposite charges attract, the paper was drawn to the glass. However, when the paper touched the glass, its charge was neutralized. The paper was no longer was attracted to the glass, and so fell away.
Procedure: Just barely open a water faucet so that you get a very fine stream of water flowing. Then, run the
comb through your hair several times. Slowly bring the comb near the stream of water. What do you see?
What Happened: From previous experiments, you already know that the comb is charged with static electricity. When you bring the comb near the stream of water, you see it bend toward the comb. There is a slight charge on each of the water molecules that draws them toward the charged comb.
Needed: Meter or yard stick, or dowel, or other
long stick; two chairs; two balloons; string; piece of glass
from a picture frame; flannel or silk cloth.
Procedure: Blow up the two balloons and tie each off with a length of string. Place the stick across the two chairs and suspend the two balloons so that they hang freely about two inches apart.
Rub each balloon across your head several times, and then allow the balloons to hang freely again. What happens? Next, rub the piece of glass with the cloth, and then bring the piece of glass between the two balloons. What happens now?
What Happened: Rubbing the two balloons on your head gave each a negative charge. The two balloons then had like charges, and this caused them to repel each other. Like charges repel.
When you rubbed the glass with the flannel or silk, you gave it a positive charge. When you put the glass between the balloons, the negatively charged balloons were attracted to the positively charged glass because unlike charges attract.
An electroscope is a device that
will detect very small charges of static electricity.
Materials Needed: ½ liter (16-20 ounce) plastic or glass soft drink bottle with plastic screw cap; piece of insulated heavy gauge copper wire; aluminum foil; modeling clay; plastic comb.
Procedure: Wash the bottle and remove the label. Allow the bottle to dry thoroughly. Using a sharp nail, punch a hole in the center of the plastic cap. This hole should be just a little larger than the wire you are using.
Cut a piece of wire just a little shorter than the bottle. Remove about 2 cm (½ inch) of insulation from one end and about 4 cm (1 in) from the other end. Using a pair of pliers, bend the end with 4 cm (1 in) stripped off into a squared “J” shape as shown below.
From underneath the cap, stick the straight portion of the wire through the hole in the cap so that about 4 cm (1 in) or so of insulated wire is above the cap. Place a small amount of modeling clay around the wire on top of the cap to hold it firmly in place.
Next, cut a piece of aluminum foil about 15 cm (6 in) long and 1 cm (1/4 in) wide. (You should use thin foil rather than the thicker “heavy duty” type.) Fold this strip in half and cut it in two at the fold. Punch a hole near one end of each piece of foil. Hang each piece of foil over the “J” on the wire. Make sure that the two halves of the foil are close together but that they do not quite touch. Insert the foil and wire into the bottle and screw on the cap.
you hair several times with the comb. Bring the comb
the bare wire at the top. Watch the foil as you
What To Look For: The foil halves should repel each other.
What Happened: The comb was charged with a negative charge. This negative charge was created on the comb as it picked up extra electrons from your hair. When the comb was brought close to the copper wire, some of the electrons moved from the comb to the wire and from there down to the foil. When the electrons reached the foil, they spread out over both pieces of the foil. Since both sides of the foil then had a like charge (negative), the sides repelled each other.
Going Further: Try charging a drinking glass with a flannel or silk cloth. What happens if you bring the glass near to the wire while the leaves of foil are spread out from the negative charge? Why?
There's much more to learn about
electricity. For more interesting
the Current Electricity and Simple