Van De Graaff Generator


The Inspiration

Robert J. Van De Graaff studied at Oxford and became increasingly interested in the study of accelerating particles for the use of nuclear research. He started to realize that these charges could accumulate inside a metal sphere, this was the catalyst for his invention of the Van De Graaf Generator. (Gale)

The Real Life Uses

Sterilize food

Process materials

Accelerating protons for nuclear experiments

Driving x-ray tubes


To create a charge that can be used for the aforementioned needs, it uses electrostatics. By using friction the Van de Graaff Generator can attract electrons to the belt of the generator and brings them to the dome, thus repelling electrons and attracting protons. (Blake)

How It Works


Van De Graaff generators are run by a single electric motor in the base. There will be a switch at the base f the generator. By turning it on the ball will become charged, this is how:


In the bottom of the generator there is a motor. The motor is attached to a plastic pulley inside the lower end of a rubber belt. This belt runs up to the metal dome.
There is a copper comb that is connected at the back by a wire to electrical ground. The teeth of the comb are almost touch the bottom of the rubber belt. (J. Bean)


The comb is made of plastic so its atoms hold on to their electrons more weakly than the rubber atoms of the belt. Because of this, the friction of the belt and pulley can make the electrons of the pulley to jump to the inner surface of the rubber belt. This leaves those plastic atoms with a net positive charge. (Bean)


The bottom pulley loses electrons to the inner surface of the rubber belt because of friction. The positive atoms remain on the pulley, but the electrons that are moved are spread all over the rubber belt. "So the pulley’s positive charge is more concentrated than the negative charge of the belt." (Bean) The comb, that is grounded, can supply as many electrons as it needs. These electrons feel the positive charge of the pulley and some jump across to the comb. (Bean)


As the belt moves away from the bottom, it now has extra negative charges on all surfaces. All of these electrons repel other electrons and the electrons coming in could, they would jump to the comb to try and get away but they are trapped on the insulating surface of the rubber belt. (Nave) (Bean)


This energy from the electrons on the dome can create sparks, attract pith balls, or make your hair stand up. As the electrons move up the belt, the generator has to work harder to bring them to the dome because of the repulsion between the negative charges. Thus the energy that went into the motor is changed to the energy of charge separation and does not move. (Nave) (Bean)
How Does a Van de Graaff Generator Work?


Works Cited

Source Citation


"Robert J. Van de Graaff." Notable Scientists from 1900 to the Present. Ed. Brigham Narins. Detroit: Gale Group, 2008. Gale Science In Context. Web. 7 Feb. 2013.

"Robert van de Graaff." World of Invention. Gale, 2006. Gale Science In Context. Web. 7 Feb. 2013.


R. Nave. "Van De Graaff Generator." HyperPhysics. No Date. . 11 Feb 2013. <>.

John C. Bean. "Van De Graaff Generators." UVA Virtual Lab. 2003-2012. University Of Virginia. 12 Feb 2013. <>.

*Note* All pictures that were not cited are from this source


Blake, Leesa, et al. ON Science 9. Whitby, ON: McGraw-Hill Ryerson, 2009. Print.