A Van de Graaff generator is a device that uses a moving belt to accumulate static electricity on an insulated metal dome. It was invented by American physicist Robert J. Van de Graaff in 1929. The device works by using a motor to drive a belt made of insulating material, such as rubber or nylon, around two rollers. One of the rollers is connected to a high voltage source, while the other roller is grounded. As the belt moves, it picks up electrons from the high voltage source and transfers them to the grounded roller, thus creating an electrostatic charge on the metal dome above it. This charge can then be used for experiments in physics and chemistry or for producing spectacular sparks and lightning-like displays.