ELECTROSTATICS - Electric Fields A conducting ping-pong ball is suspended by thread and placed on the outer surface of one of the plates of a parallel-plate capacitor. As the plates are charged with the Wimshurst machine, the ball follows the fringing electric field lines between the outer surfaces of the plates. The ball can also be placed between the plates, in which case it bounces repeatedly between the plates. http://en.wikipedia.org/wiki/Wimshurst_machine