Leyden jar

The Leyden jar was the original capacitor, developed in the 18th century and used to conduct many early experiments in electricity.

History

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The ancient Greeks used balls of amber on spindles that they rubbed to generate sparks. This is the triboelectric effect, mechanical separation of charge in a dielectric. Their work was a precursor to the development of the leyden jar.

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Around 1650, Otto von Guericke built a crude friction generator - a sulphur ball that rotated at high speed on a shaft. When Guericke held his hand against the ball and turned the shaft quickly, a static electric charge built up. In 1745, another German, Ewald Jürgen Georg von Kleist, found a method of storing this charge. He lined a glass jar with silver foil, and charged the foil with a friction machine. Kleist was convinced that a substantial charge could be collected when he received a significant shock from the device. This invention went on to be known as the Leyden jar because in 1746, Pieter van Musschenbroek of the University of Leiden, Netherlands, independently made the same discovery. Musschenbroek made the storage jar known to the scientific world, hence the jar was named after Leiden, the home town of the university.

Related Topics:
Otto von Guericke - Friction - Generator - Sulphur - Electric charge - 1745 - Ewald Jürgen Georg von Kleist - Silver - Pieter van Musschenbroek - University of Leiden - Netherlands - Leiden - University

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The physicist James Clerk Maxwell invented the concept of displacement current, dD/dt, to make Ampere's law consistent with conservation of charge in cases where charge is accumulating, for example in a Leyden jar. He interpreted this as a real motion of charges, even in vacuum, where he supposed that it corresponded to motion of dipole charges in the ether. Although this interpretation has been abandoned, Maxwell's correction to Ampere's law remains valid (a changing electric field produces a magnetic field). The displacement current must be included, for example, to apply Kirchhoff's current law to a Leyden jar.

Related Topics:
James Clerk Maxwell - Displacement current - Ampere's law - Dipole - Ether - Kirchhoff's current law

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