Description
Leyden jars are used to store electric charge and were a very early form of capacitor (a device used to store electric charge in electronic equipment such as a television or computer). The device was named “bouteille de Leyden”. This was after the first experiments that were carried out by Peter Musschenbroek and Andreas Cunaeus in Leyden, Holland in the 1740’s.

The discovery of the leyden jar was very important in the development of electrical theory in the second half of the 18th century. It became possible to study more powerful electrical charges and develop new concepts such as the electrical circuit, the area of surface electrified and the amount of charge. Before the invention of the leyden jar the electric charges that were produced could not be contained anywhere for long enough to be used or studied.

To use the leyden jar, it would have been first charged by an electrostatic machine such as a Wimshurst machine. The electric charge flows down the metal chain or rod to a metal coating inside the jar, consisting of lead or tin foil. Because of the glass material of the jar the electricity cannot leak out and so builds up inside the jar. To discharge the jar a curved rod was used which would have been held near the metal ball on the lid and the outer foil of the jar which causes a spark to occur.