lab: Constructing an Electroscope

GRADE SCHOOL LAB
CONSTRUCTING AN
ELECTROSCOPE

INTRODUCTION:

An electroscope is used to detect an electrical charge. If you rub a balloon on your hair, electrons are rubbed off of your hair and onto the balloon, giving the balloon a negative charge. When the negatively charged balloon is held near the metal loop, electrons on the surface of the metal move away from the balloon and down the wire. As these electrons build up on the aluminum strips, the now negatively charged strips move apart (repel each other).

In this project, you will construct an electroscope, and use it to observe how objects with like charges repel each other.

MATERIALS NEEDED:

*Aluminum foil
1 quart glass jar
Soft plastic lid to cover top of jar
Large paper clip
Modeling clay
Needle-nose pliers
Scissors
Pencil
9 inch round balloon

* The aluminum foil needs to be as thin as possible. Store brands are typically thinner than name brands. You can lay the foil on a clean flat surface, and rub it with your thumb in all directions. This will thin the foil a little. The best foil to use is from a chewing gum wrapper. Cut it to size before removing the paper from the foil. You will probably tear several before you get two good ones, but this foil will work much better.

PROCEDURE:

Construction

Use the pliers to reshape the paper clip into a loop with two hooks on the bottom, as illustrated.

Use the pencil to make a hole in the center of the plastic lid. NOTE: If you could not get a soft plastic lid, have an adult use an electric drill to drill a hole in a hard plastic lid for you.

Push the loop if the wire through the hole in the center of the plastic lid and mold a small piece of clay around the bade of the loop to secure it in place.

Cut two strips of aluminum foil 1 cm X 5 cm. And using the pencil, make a small hole in the top of each foil strip.

Hang the foil strips on the wire hooks. Adjust by carefully bending the wires, so that the wide faces of the strips are hanging close to each other but not touching.

Place the lid on top of the jar. Your electroscope is now complete.

Using your electroscope

Inflate the balloon and tie it off. Rub the balloon on your hair. Your hair must be clean, dry, and oil-free.

Hold the balloon near the loop, on top of the jar. Observe the behavior of the foil strips.

Try other objects such as a plastic comb that has been combed through your hair, or a plastic rod rubbed on a piece of fur.

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