Electrophorus n. : An instrument for exciting electricity, and repeating the charge indefinitely by induction, consisting of a flat cake of resin, shelllac, or ebonite, upon which is placed a plate of metal.

Example:
Trying to Understand Electrophorus experiment ?

Taxonomy
electrophorus, metal plate, dielectric, 2007-12-27, Encyclopaedia Britannica, free encyclopedia, invention, bearer, Pancaldi, google, Thomas B. Jones, Jones website, Univ. of Rochester, cake, rubbing, negative charge, negative charges, neutral.

Defination from the web:
electrophorus consists of a dielectric plate (originally a 'cake' of resinous material like pitch or wax, but in modern versions plastic is ... The electrophorus is thus actually a manually operated electrostatic generator, using the same principle of electrostatic induction as ...