The objective of this experiment is to demonstrate the repelling force between two objects of the same charge.
2 equally sized balloons (the experiment can also be performed using
plastic stick pens)
2 feet of string
a wool cloth (other fabrics will also work)
How To Build It
Blow up the balloons to equal size. Now tie a piece of the string to the end of each balloon.
Hold the string at its center and allow the balloons to hang down. The balloons simply bounce into each other. Now rub the wool cloth across both of the balloons where they made contact with each other. Let the balloons go again. Notice how this time they do not touch. They now repel each other.
If the balloons do not repel each other after you have rubbed the wool across them, try the following:
Experiments with Everyday Objects by Kevin Goldstein-Jackson. Prentice-Hall, Inc. 1978. p. 156.