The Electrophorous has something of the perpetual motion machine about it. When writing to Joseph Priestly in 1775 Allesandro Volta (1745-1827) noted that it was a device that "electrified but once, briefly and moderately, never loses its electricity."
| The modern form of the electrophorous is shown
at the right. This example, in regular use at Kenyon College, from the
first quarter of the 20th century, has a hard-rubber dielectric plate 29
cm in diameter.
The plate is first charged (negatively) by rubbing it with rabbit fur, and the plate laid atop it. The presence of the negative charge causes a separation of charge in the plate, with the positive charge being held on the bottom of the plate. Touching the top of the plate with the finger allows the un-bound negative charge to disappear into the body, a charge reservoir. The positively-charged plate is then lifted by its handle. and a spark drawn from it. In my own demonstrations I use a large neon glow lamp or a small fluorescent tube to indicate the passage of charge.