Definition of Potential

Application: Van de Graaff Generators

Van de Graaff generators were originally designed by Robert J. Van de Graaff as a way to generate high voltages used for atom-smashing.

Van de Graaff generators work by a completely mechanical method. A pointed conductor "sprays" positive charge onto the moving belt. The belt carries the positive charge to the interior of the dome where it is repelled off to the outside surface of the dome. As the positive charges accumulate, the sphere gains higher potential relative to the ground. A potential as high as 30 million volts can be obtained by this device!! In the original design, an evacuated tube (one with all the air sucked out) is attached to the domes, and a series of Hydrogen or Helium ions is accelerated toward a target.

In our example, the proton beam then gains a kinetic energy of 30 MeV and is accelerated toward a grounded nuclear target.

The Important Part: The mechanical system of a Van de Graaff generator does work to create an electric potential difference!

The Theater of Electricity at the Boston Museum of Science has the two largest Van de Graaff generators in the world, and a good on-line tour.

If you're interested in having your own working (albeit smaller) Van de Graaff generators, check out Pete Miller's page. Just remember not to try all of it at home.

Now go on to answer some questions about what you just learned. If you have already been to that page, then continue on to a discussion of Parallel Plates.


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