Electroscope

You will need :

Small glass jar
Wire coat hanger
Aluminum foil
Cardboard
Strip of silver Mylar from helium balloon or wrapping paper
Plastic comb
Balloon
Pencil
Cellophane
Rubber cement
Electrical tape
Wire clippers
Pliers


An electroscope is a simple device that measures static electricity, or the freely flowing electrical charges of the atmosphere. Static electricity is caused by friction, or something rubbing against something else. This electricity-producing friction can be as harmless as a comb rubbing against hair or powerful as ice crystals rubbing against each other in a thundercloud.


Procedure :

1. Use the wire clippers to cut off a straight piece of wire from the hanger. Use the pliers to bend a section at one end into L shape.
2. Turn the jar upside down onto the cardboard, and trace a circle around the opening.
3. Cut out the circle and punch a small hole in its center with a pencil.
4. Carefully push the wire through the hole about 1 inch (2.5 cm), straight end first.
5. With as little cellophane tape as possible, attach the middle of the Mylar strip to be bent end of the wire so that the strip hangs down in two equal halves.
6. Rubber cement the cardboard circle to the top of the jar, with the bent end of the wire holding the Mylar strip pointing down.
7. Place electrical tape around the edges where the circle touches the rim of the jar, and place a thin band of cement around the wire where it punches through the cardboard.
8. After the rubber cement dries, crumple the aluminum foil into a tight ball, and carefully push it onto the top of the wire.
9. Rub the plastic comb or balloon against your hair or clothing (wool works best), and hold either one close to the aluminum foil ball.


Result :

If the air is dry enough, the ends of the Mylar strip fly apart when comb or balloon touches the ball.


Explanation :

An electroscope shows the attraction and repulsion of electrical charges. In all electrical activity, like charges repel and opposite charges attract. When you rub the comb, friction causes a positive charge to build up in the plastic. When you hold the positively charged comb near the aluminum foil ball, the comb attracts negative charges which move up through the wire so that only positive charges remain in the Mylar strip. Since both ends of the strip now have the sama charge, the ends of the strip flay apart.


Display Tip :

Display your electroscope along with an assortment of objects for creating static charges.

Source : Science Fair Projects by Glen Vecchione