Description

Demonstrate the charging of objects by using induction.

Materials

Two metal spheres with plexi-glass bases (located in cabinet with glass doors)
Electrophorus disk
Amber or plastic rod
Fur
(Alternatively, the Wimshurst machine)
Electroscope
“Charge Scoop”

Instructions

Charge the rod by rubbing and striking it with the fur. Transfer this charge to the metal electrophorus disk. (If this method doesn’t build up enough charge, one end of the Wimshurst machine can be attached to the metal plate and it can be charged that way.) Place both spheres next to each other so that they are touching. Then bring the now charged electrophorus disk very near one of the spheres but not close enough that any charge bleeds off. When this happens positive charges move away from the disk on to the far sphere and negative charges move close to the disk on the closer sphere. While the disk is near the spheres, separate them and then remove the disk. One sphere will now be negatively charged and one will be positively charged. This can be shown using an electroscope. Scoop charge off one of the spheres and touch the electroscope, it will show a deflection. Then scoop off the second sphere and touch the electroscope again; it will return back to neural. This shows that each sphere has an equal and opposite charge.

Other

Electrostatics, Electrostatic Induction, 8.02, 8.022