Lyden Jar: Consists of a top electrode electrically connected to a metal foil coating of the inside of a glass jar. A conducting foil is wrapped around the outside of the jar. The jar is charged by an electrostatic generator connected to the inner electrode while the outer plate is grounded. The inner and outer surfaces of the jar store equal but opposite charges.
The original form was just a glass bottle filled a little with water, with a metal wire passing through a cork closing it. The outer plate was replaced by the hand of someone. It was believed that the charge was stored in the water. Now it is clear that the charge is actually stored not in the conductors, but only in a thin layer along the facing surfaces that touch the glass. The amount of capacitance was measured in number of 'jars' of a given size, or through the total coated area. A large Leyden jar has about 1 nF of capacitance.
The original form was just a glass bottle filled a little with water, with a metal wire passing through a cork closing it. The outer plate was replaced by the hand of someone. It was believed that the charge was stored in the water. Now it is clear that the charge is actually stored not in the conductors, but only in a thin layer along the facing surfaces that touch the glass. The amount of capacitance was measured in number of 'jars' of a given size, or through the total coated area. A large Leyden jar has about 1 nF of capacitance.
Wimhurst Machine: Machine created electric charges through electrostatic induction. In a Wimshurst machine there are 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 induced, amplified, and collected by two pairs of metal combs. These collectors are mounted on insulating supports and connected to the output terminals. The positive feedback increases the accumulating charges exponentially until the dielectric breakdown voltage of the air is reached and a spark jumps across the gap. The machine is self-starting and requires no external electrical power but does need mechanical power to turn the disks. The insulation and the size of the machine determine the maximum output voltage that can be reached. The output and the sparks can be increased if a lyden jar liked mentioned above is added to the output terminals.
P Boyar
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