VAN DE GRAAFF GENERATOR SCIENCE MODULE
METHOD
Voltages of hundreds of thousands of volts can be generated with a demonstration model Van de Graaff generator. Though startling, discharges from the Van de Graaff do not represent a serious shock hazard since the currents attainable are so small.
A pulley drives an insulting belt by a sharply pointed metal comb which has been given a positive charge by a power supply. Electrons are removed from the belt, leaving it positively charged. A similar comb at the top allows the new positive charge* to spread to the dome.
A favorite demonstration with the Van de Graaff is to make someone's hair stand on end.
Puffed Wheat Shower
Puffed wheat cereal makes a good demonstration of electrostatic repulsion. The charges which have been collected on the outside of the sphere can get further apart by transferring to the puffed wheat. Then they are repelled by the charge on the Van de Graaff and fly off. Our observations are that a few of them remain behind and do not lift off even after a minute or two of running the Van de Graaff. We don't know why -- they appear to be identical to those which do lift off. The plastic bowl is attached to the Van de Graaff dome with masking tape so that it doesn't fly off.
There are several other experiments that can be done with this. A favorite with the kids.
