homopolar generator

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A simple electric generator consisting of a metal disk rotating between two poles of a magnet. Contacts are made to the axle and the rim of the disc. A radial e.m.f. is produced. At constant rotational speed, the device produces a steady direct current and generators of this type are used in certain specialized applications. It can also be used as a simple motor if a direct current is supplied. A device of this type (known as the Barlow wheel) was invented in 1822 by the physicist Peter Barlow (1776–1862). This had a star-shaped wheel with the points of the star dipping into a pool of mercury to give the electrical contact. A generator with a disk was used by Michael Faraday in his experiments, and the device is sometimes known as the Faraday disk.

Subjects: Physics.

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