Franklin's bell

Two metal cans are placed on insulating supports. One can is electrically connected to the earth and the other is connected to a Van de Graaff generator. A metallic cotter pin is suspended between the bells by a dielectric thread. The Van de Graaff would allow charge to build up on the can which would then attract the metallic cotter pin. When the pin hits the first can it will become charged to the same potential and therefore will be repelled again. Since the opposite can is charged oppositely this will also attract the pin towards it. When the pin touches the second can the charge is transferred and the process repeats.

In 1752 Benjamin Franklin was experimenting with one of his inventions, the lightning rod. Using the similar setup shown above Franklin was able collect electrostatic charges from the wind above his house. No known images exist of the original setup used, but this is the most common method used to reproduce the effects he describes.