Thank you for visiting my booth at the USA Science and Engineering Festival. I hope you had a great time. Below is some more information about the machines I demonstrated at the festival, as well as links to resources for making your own.
The electrophorus is capacitive generator, and produces charge through electrical induction. A rabbits fur or cloth gives up electrons to the insulating plate when it is rubbed onto it. The brass plate is then placed ontop of the insulator, and grounded (this is done by pressing a finger onto the brass plate). When the plate is lifted via the insulating handle, a charge is lifted with it. This charge can then be used in various experiments.

Here is some more detailed information on the function of an electrophorus. And here are some links to instructions for making your own.

The electroscope is an early version of a voltmeter. It is a way of detecting an electrical charge. In the presence of an electrical charge, the two halves of the gold foil become charged the same, and so they repel. Measuring the angle of deflection provides a way of comparing relative charges. This type of electroscope with windows on the front and the back of the device was used in lectures, and allows a light to pass through the instrument, which would cast a shadow, and allow a large audience to view the measurement.

Here is a nice page full of historical instruments. Here are some instructions I put together so you can make your own electroscope. Print Quality version here. (This is a very large file).

Kelvin (Water drop) Generator
The Kelvin Generator is a classic physics experiment. The machine is a type of induction generator. A charge imbalance in the system is reinforced as it is running, building and building the charge, until it arcs across the spark gap, to balance itself out.

Here is a link to a youtube video of a lecture from MIT, the Kelvin Generator is explained in detail, the demonstration of the machine happens around 47:28. This webpage has pretty good instructions on making your own waterdrop generator, although the graphics are a little too 1978.

Finally, the best resource on the internet for information regarding electrostatic machines is Antonio Carlos M. de Queiroz's page. It contains information on practically every major type of electrostatic device. If you have the itch to try making something more "sparky", and consequently more dangerous, check out the forums and wikis at