|Volta the electrifying physicist
1. The electrophorus
The first electrical instrument created by Volta was the electrophorus (1775). Basically it was an adaptation of the Franklins plate. Since resins in general are more tenacious when it comes to holding an electrical charge, Volta replaced the glass by resinous mastic. He also replaced the flat upper armature by a rounded mobile shield, to get rid of the corners which encourage electricity to disperse.
The perpetual electrophorus at work
If the electrophorus is charged by contact with an electrostatic machine (+ on the shield and - on the lower armature) and then the two armatures are short circuited with each other, all signs of the presence of electricity disappear.
If, at this point the shield is raised and kept insulated, strong electrical signs are found on the shield and on the resin.