Wikipedia
A Van de Graaff generator is an electrostatic generator which uses a moving belt to accumulate electric charge on a hollow metal globe on the top of an insulated column, creating very high electric potentials. It produces very high voltage direct current (DC) electricity at low current levels. It was invented by American physicist Robert J. Van de Graaff in 1929. The potential difference achieved in modern Van de Graaff generators can reach 5 megavolts. A tabletop version can produce on the order of 100,000 volts and can store enough energy to produce a visible spark. Small Van de Graaff machines are produced for entertainment, and in physics education to teach electrostatics; larger ones are displayed in science museums.
The Van de Graaff generator was developed as a particle accelerator in physics research, its high potential is used to accelerate subatomic particles to high speeds in an evacuated tube. It was the most powerful type of accelerator in the 1930s until the cyclotron was developed. Today it is still used as an accelerator to generate energetic particle and x-ray beams in fields such as nuclear medicine. In order to double the voltage, two generators are often used together, one generating positive and the other negative potential; this is called a tandem Van de Graaff accelerator. For example, the Brookhaven National Laboratory Tandem Van de Graaff achieves about 30 million volts of potential difference.
The voltage produced by an open-air Van de Graaff machine is limited by arcing and corona discharge to about 5 megavolts. Most modern industrial machines are enclosed in a pressurized tank of insulating gas; these can achieve potentials up to about 25 megavolts.
Usage examples of "van de graaff generator".
It was a great pleasure for Lydia and Enzo to take their grandchildren to the Museum of Science in Boston to witness the lightning bolts thrown off by that machine which is called a Van de Graaff generator.
Lightning jerked and jumped between one hand and the other, like a Van de Graaff generator.
The Van de Graaff generator provided a crude but effective way of converting electricity to light.
But there were also some pieces of apparatus more familiar from her own school days: Bunsen burners and big chunky electromagnets and what looked like a Van de Graaff generator.