#63

The Wimshurst machine was developed between 1880 and 1883 by a British inventor James Wimshurst. It created electric charges through electrostatic induction. It has two large contra-rotating discs mounted in a vertical plane, two cross bars with metallic brushes, and a spark gap formed by two metal spheres. The two insulated discs and their metal sectors rotate in opposite directions passing the crossed metal neutralizer bars and their brushes. The machine does not need any initial charge, but it does require mechanical power to turn the disks against the electric field. A difference of charges is induced and collected by the two metal combs near the surface of the discs. These collectors are put on insulating supports and attached to the output terminals. If there is positive feedback it will increase the accumulating charges continually until there is a spark that jumps across the gap which means there is a dielectric breakdown voltage of the air. The Leyden jar can be used to increase the accumulated spark energy.
The Leyden jar was invited in 1745 by Pieter van Musschenbroek. It is an early device for storing electric charge. This device was used to conduct many early experiments in electricity. Its appearance is a top electrode electrically connected usually by a chain to a metal foil coating part of the inner surface of a glass jar. Another foil is wrapped around the outside of the jar to match the internal coated area. The electrostatic generator is what the jar is charged by is connected to the inner electrode while the outer plate is grounded. Therefore the inner and outer surfaces of the jar store equal but opposite charges. The initial form of the Leyden jar was a glad bottle partly filled with water. It had a metal wire passing through a cork. The experimenter would take the role of the outer plate. Originally he believed that the charge was stored in the water. However, Benjamin Franklin investigated that the Leyden jar was actually stored in the glass, but only in a think layer along the facing surfaces that touch the glass.