Electrophorus

For the genus of fish family Electrophoridae, see electric eel

An electrophorus is a single-plate capacitor used to produce imbalances of electric charge via the proces of electrostatic induction. The electrophorus was devised long ago in the18th century by Johannes Wilcke and Alessandro Volta.

The electrophorus consists of a dielectric plate or 'cake' on a metal surface and a metal plate with an insulating handle. First, the dielectric plate is charged through contact electrification, that is, by triboelectricity. Then, the metal plate is placed onto the dielectric plate. The metal plate develops two regions of charge induction - the side facing the charged dielectric plate charges opposite to the charge of plate, while the side facing away from the dielectric charge attains the same sign of charge as the dielectric plate, with the mteal plate remaining electrically neutral as a whole. Then, the side facing away from the dielectric plate is momentarily grounded, draining off the excess alike charge. Finally, the metal plate, now carrying only one sign of charge, is lifted.