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The Wimshurst machine is a historical electrostatic machine for generating high voltages, and was developed between 1880 and 1883 by British inventor James Wimshurst (1832 – 1903). It is an electrical generator with a distinctive appearance, having two large contra-rotating discs mounted in a vertical plane, and a spark gap formed by two metal spheres.
Description
The machine belongs to a class of generators called influence machines. These machines work by separating electric charges by electrostatic induction, or influence. Earlier machines in this class were developed by Wilhelm Holtz (1865 and 1867), August Toepler (1865), and J. Robert Voss (1880). They were more efficient than the earlier machines that worked by friction. The earlier machines exhibited a tendency to suddenly and without warning switch their polarity. The Wimshurst machine did not suffer from this defect.
The operating principle of the machine is based on two counter-rotating disks made of insulating material. Each disk has several metal segments attached to it, called sectors. As the sectors pass one another, they induce a charge imbalance on one another. This imbalance is drained off at the collecting electrodes.
The machine is self-starting, meaning that it requires no electrical power supply to create the initial charge. It does, however, require mechanical power to turn the discs. The output of the machine is a constant current. The spark energy can be increased by adding a Leyden jar, which is an early type of capacitor suitable for high voltages.
External links and references
- "History of Electrostatic Generators". Hans-Peter Mathematick Technick Algorithmick Linguistick Omnium Gatherum.
- de Queiroz, Antonio Carlos M., "Electrostatic Machines".
- de Queiroz, Antonio Carlos M., "The Wimshurst Electrostatic Machine"
- Weisstein, Eric W., "Wimshurst Machine".
- Bossert, François, "Wimshurst machine". Lycée Louis Couffignal, Strasbourg. (English version)
- Charrier Jacques "La machine de Wimshurst". Faculté des Sciences de Nantes.