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The National MagLab is funded by the National Science Foundation and the State of Florida.

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Electrostatic Generator

Though simple by today's standards, the early electrostatic generators were a great milestone in humankind's understanding of electricity.

Humans have long known that rubbing substances together can produce static electricity. The ancient Greeks rubbed together balls of amber on spindles to generate sparks. Electrical effects puzzled early scientists, but they lacked a means of generating electricity in order to study it.

Then, in the mid 1600s, German physicist Otto von Guericke came up with a very early version of a machine that did just that: the electrostatic generator. A version of the machine dating from 1785 is pictured here. It generates a high voltage charge at very low current.

Instructions

  1. The device consists of a glass cyclinder connected to a hand crank.
    2. On the left side, a piece of leather is mounted against the cylinder. On the right side is a metal comb connected to a metal ball. The yellow balls represent electrons
  2. Click the button to turn the crank on or off.
  3. As the cylinder rotates, the leather pressing on the moving glass causes positive ions to collect on the leather. This in turn causes negatively charged electrons to stick to the glass.
  4. On the other side, the comb-shaped metal collects the electrons. As the electrons build up, the charge can jump as a spark from the metal ball to the ball on the top of the nearby capacitor called a Leyden jar, where the charge can be stored.
  5. Move the separation slider to see how a greater build-up of charge is needed to create a spark as the distance between the metal balls is increased.