Van de Graaff Generator
A Van de Graaff generator is a device used to create a high voltage static charge. In this Van de Graaff generator, an electric motor pulls a latex belt over a felt covered pulley. Electrons are transferred from the felt to the belt as the belt pulls away from the pulley. The electrons ride the belt to the upper dome, where a pick-up wire transfers them from the belt to the dome. Each electron carries a negative charge and, since like charges repel, the electrons on the dome attempt to get as far away from each other as possible. At some point, too many electrons are placed on the dome. When this occurs the electrons attempt to reach the earth by leaping through the air to a nearby object, creating a large spark.
You can watch experiments using a Van de Graaff generator in Frostbite Theater.