Physics Dept. Demonstration Manual

DEM79 - Electrostatic Ping Pong


to demonstrate attractive and repulsive electrostatic forces.

  • custom DEM79 device
  • Wimshurst machine
  • two banana-alligator leads.


Connect the DEM79 apparatus to the Wimshurst machine. While cranking the machine swing the conducting sphere such that the sphere touches one of the charged plates. The sphere will become like charged, be repelled, and swing across the gap to hit the opposite plate. Charge transfer again takes place and the sphere swings back to the first plate and so on. The sphere will continue the back and forth oscillation for as long as one provides "fresh" charge via cranking the Wimshurst machine.

After the cranking has stopped there is sufficient capacitance to allow oscillation to occur for a number of additonal swings.