The Leyden jar originated in 1746. It consists of a glass jar with an outer and inner metal coating covering the bottom and sides up to the neck. A brass rod in an external knob passes through a wooden stopped and is connected to the inner coating by a loose chain. When an electrical charge is applied to the external knob, positive and negative charges come from the two metal coatings respectively, but they are unable to discharge because of the glass between them. This results in the charges holding each other at equilibrium until a discharge path is provided. These jars were first used to store electricity in experiments and later as a condenser in early wireless equipment.
The Wimshurst machine is an electrostatic device used to generate high voltages between 1880 and 1883 by British inventor James Wimshurst. In this machine, the two insulated disks and their metal sectors rotate in opposite directions passing the crossed metal neutralizer bars and their brushes. An imbalance of charges is then induced, amplified and collected by two pairs of metal combs with points placed near the surfaces of each disk. These collectors are mounted on insulating supports and connected to the output terminals. The positive feedback increases the charges exponentially until the dielectric breakdown voltage of the air is reached and a spark jumps across the gap.
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