File:Dissectible Leyden jar.png

English: Drawing of a "dissectible" Leyden jar, from 1876 physics book. This experimental apparatus, invented by American statesman and scientist Benjamin Franklin, was used to illustrate an erroneous belief that the charge on a Leyden jar does not reside on the metal plates, but on the glass jar dielectric. The jar was assembled and charged with electricity. If the jar was then disassembled into its parts, it was found that the parts were not charged and could be handled without creating a spark. However, if the jar was then reassembled, a spark could be obtained between the inner and outer metal plates. This was supposed to show that the charge in Leyden jars, and all capacitors, is stored in the dielectric, not the metal plates. However, it is now known that this was a special effect caused by the high voltage on the Leyden jar. When the jar is disassembled, the charge is deposited on the glass by corona discharge. Handling does not remove much of the charge, so when the jar is reassembled there is enough left to cause a spark. In general the charge in capacitors such as Leyden jars is stored on the plates.