Make a Static-Charge Finder

The drawing explains how to put one together. (You may need an adult’s help to remove any covering from the ends of the wire.)

To test the electroscope, make a static charge by rubbing an inflated balloon against your clean, dry hair. When the balloon has a static charge, it will attract tiny bits of dry paper from one or two inches away.

If you hold the charged balloon near the top end of the wire, the two flaps of aluminum foil will move apart. If they do not, try different types of foil, wire, and clay, changing only one at a time.

Once the electroscope works, use it to detect static charges by bringing it close to electrical equipment, such as a television screen or computer screen. Never stick the wire into any kind of appliance or outlet. That could give you a dangerous shock.

How It Works
When you rub the balloon against your hair, the balloon takes negatively charged particles, called electrons, from your hair. Then both the balloon and your hair have a small charge of static electricity. Your hair has a positive charge, and the balloon has a negative charge.

Since any two objects with the same charge push away from each other, the balloon pushes away anything that also has a negative charge, including electrons.

That pushing makes the electroscope work. When the balloon comes close to the wire, the balloon’s negative charge pushes some of the wire’s electrons down into the foil strip. Some electrons go into one side of the foil, and others go into the other side. Now both foil flaps have a negative charge, and they push away from each other. The stronger the charge, the wider they open.

1. Remove the label from a twenty-ounce soda bottle. Rinse out the bottle and let it drain until completely dry. 2. Bend a five-inch-long piece of wire as shown. (The wire from a long twist tie worked for us.) Make sure that the ends are bare metal. 3. Cut a three-inch-long strip of aluminum foil, fold it, and hang it on the wire. Make the two flaps hang straight down. They should not have any rough edges or anything else that might make them stick together. 4. Form a ball of modeling clay around the wire, near the top. Lower the aluminum-strip end of the wire into the center of the bottle. Gently press down on the clay to seal the bottle.