Van de Graaff generator for 500kV

This page is about my big 500kV Van de Graaff generator with a 14"/35.5cm dome, which is what allows it to get up to such a high voltage.

Big Van de Graaff generator doing the 'hair raising' demo.
Big Van de Graaff generator doing the 'hair raising' demo.
A spark (3.25"/8.3 cm).
A spark (3.25

It was purchased from Information Unlimited in 2002, and though they don't have the same one there now, there are comparable ones. The original manufacturer is Science First, which also sells them.

The parts - how the Van de Graaff is made

There is how this Van de Graaff generator is made. Below is a photo showing an overall view. More detail is given lower down.

Parts overall view.
Overall view of the Van de Graaff generator parts.

The bottom is a metal box and in the above photo the top has been removed to show what's inside. It was designed to be removable since you need to if you ever need to replace the belt or do some cleaning.

As shown below, inside it is the AC motor which is powered through a power cord that plugs into the wall socket. The plug has the ground prong and that's where this Van de Graaff gets its ground connection. A green wire inside connects the metal case to that ground.

Motor, plug, ground, ...
Van de Graaff's motor, plug, ground, ...

Also electrically connected to the case, and therefore to ground, is the bottom brush. The bottom brush is a sheet of stiff copper mesh, cut such that the edge facing the bottom roller has sharp points.

The bottom roller is teflon.

Bottom roller and brush.
Van de Graaff generator's bottom roller and brush.

The 1.75"/4.4 cm wide belt is rubber and the package came with a spare rubber belt. However, the original belt is still good after already being on the machine for over 15 years. I haven't used it more than a few times a year, and some years not at all, but it's still impressive that the rubber hasn't hardened or become britle as often happens with rubber. Replacement belts are available from Science First, though make sure you have the right one if you buy one.

As shown below, the top roller is metal.

The top brush is stiff copper mesh, just like the bottom one, and has sharp points along the edge facing the roller. The brush makes electrical contact with the dome with a metal plate that descends down to where the dome sits on a ring support.

Top roller, brush, ...
Van de Graaff generator's top roller, brush, ...

The dome has 14"/35.5 cm horizontal diameter and is 9"/22.8 cm high. The roundness of a dome is the main thing that determines how high a voltage a Van de Graaff generator can get to. So a larger dome means a higher voltage.

Video - Van de Graaff Generator Demonstrations and Explanations

Various demonstrations that you can do with Van de Graaff generators, using this big Van de Graaff for many of them.

Video - How a Van de Graaff Generator Works

This video uses this big Van de Graaff to explain in detail how a Van de Graaff generator works.
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