Electric Fleas

Rubbing charges Styrofoam balls with electricity, making them jump. This makes electrical forces visible even though they are normally invisible.

The Science Behind It

Rubbing creates an electrostatic charge on the plate. Electrical charges shift and are transferred to the Styrofoam balls. The balls all end up with the same charge and repel one another. At the same time, they are attracted to the charged plate, so they jump up and then fall back down. This alternating attraction and repulsion keeps the balls bouncing. Your body can also carry an electric charge, so you can influence the balls’ movement with your hand. The exhibit shows how electrical forces work even though we cannot see them.