A capacitor is built ("sparing no expense," as the trash bag dielectric is displayed) from two sheets of aluminum foil and a plastic sheet dielectric laid out on the demo table. A DC high voltage supply is attached to a variac to provide the charge for the capacitor. When charged to 100 - 200 volts, a spark can be produced and heard by touching the lead connected to the bottom foil to the top foil.
The location of the field can be shown by charging the arrangement, disconnecting the power supply, and CAREFULLY dissassemling the foil and the plastic. When put back together, a discharge can be heard when shorted out.
The supply can also be raised until the dielectric breaks down and sparks can be heard.
An alternative to the high voltage DC source is the electrophorus disk and a glass beaker capacitor. It takes several charges from the electrophorus since it's capacitance is so much lower that the disectible capapcitor. Use an insulating tool to disassemble the capacitor, then touch all the parts to show they have no charge, then reassemble and discharge. (Location 10C3)
