Electrostatic Induction

PIRA 5A40.23

The ball shown at near right is a ping-pong ball coated in colloidal graphite.  When brought near a charged Van de Graff generator, both the initially neutral ball and the pop cans will be attracted to the generator due to induction. 

Once allowed to touch, they will be strongly repelled by the generator.  They will also be attracted to a nearby grounded sphere, again through induction.  Noisy games of ping-pong and kick the can be played if the Van de Graaff is left on and the grounded sphere is close enough.