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What Is a Wimshurst Machine?

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  • Written By: Karize Uy
  • Edited By: Lauren Fritsky
  • Last Modified Date: 03 October 2014
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The Wimshurst machine was a revolutionary generator in the 19th century that created static electricity that could generate a powerful voltage. It was categorized as an “influence machine,” since it did not use friction in generating voltages. The machine was invented and finished in 1883 by a British inventor and engineer named James Wimshurst. The Wimshurst machine was very well-received because it had the ability to generate higher voltages than other generators in its time, and it did not have any failures such as polarity switching. Centuries later, the machine is still being made to demonstrate how static electricity works.

The most noticeable things about the Wimshurst machine are the two thin discs with holes in the middle, which have a cylinder inserted on them to mount the discs onto the base. Attached to the cylinder are two thin metal rods — one for each disc — that have metallic brushes on both ends. On the left and right side of the machine are two other metal rods called “electrodes,” distinguished by the balls on their ends. Another pair of horizontal metal rods called the “collecting combs” is installed on both sides of the machine, with rubber stoppers on one of the ends; the other ends of the collecting combs are inserted in Leyden jars, called the capacitors. Basically, each side should look alike and contain the same components such as the brushes and the collecting combs, except for the electrodes that are installed on just one of the discs.

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The Wimshurst machine operates when the two discs are rotated, usually with the use of a handle, like in a wind-up box. The discs are said to “counter-rotate,” or rotate opposite each other’s direction. One can suppose that the back disc is charged negatively, and when this negative charge lines up with one end of the metallic brush on the front disc, a positive charge is created to balance out the negative charge. The other end of the brush, however, produces a negative charge, since the other end contains a positive charge.

Once negative and positive charges are present on the front disc of the Wimshurst machine, the back disc is triggered to generate positive and negative charges as well, in order to create negative-positive polarities. This process continues as long as the discs are counter-rotating, until so many positive and negative charges are being induced that it cannot be contained and they “explode” into tiny sparks. It can be visualized that the discs can only hold a positive and a negative charge, so when the extra charges pass by the collecting comb, the latter collects the charges and stores them inside the capacitors. One comb collects all the negative charges in one jar, while the other comb collects the positive charges in another jar.

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