Your Admirer is a balloon!

Materials

• Balloons
• String
• Felt-tip markers (permanent)
• Adhesive tape
• Wool cloth

Background

Wool cloth readily gives up electrons to other materials it touches. Rubbing a balloon with a wool cloth allows the balloon to accumulate an excess of electrons, and it will become negatively charged. The rubbed portion of the balloon will then be attracted to positively or neutrally charged objects (by induction), and repelled by other negatively charged objects. If the balloon is permitted to touch an object that is not negatively charged, some of the excess electrons will be transferred and the degree of attraction will decrease.

Procedure

Although this activity is an excellent teacher demonstration, students will gain more from the opportunity to make and experiment with their own "admirers."

• Inflate a balloon and draw a face on it with a permanent marker. (Caution: some types of permanent marker may weaken the balloon and cause it to pop.)
• Tie off the balloon and suspend it from a doorway or ceiling using tape and string. The balloon should hang at the level of your head when you stand on the floor.
• Rub the face of the balloon with a wool cloth. The balloon will now face you and move toward you whenever you approach it. You now have an admirer!
• Try to determine how far away the attractive force is able to act. Is the balloon still attracted toward you if you position a piece of cardboard between the balloon and your face? Can you wind up the string without touching it by making the balloon follow you round and round in a circle?
• How do you think your admirer will react if you create another admirer? Draw a face on a second balloon, rub its face with wool, and suspend it near the first admirer. Describe the way they react to each other.