Discharging an Electroscope by Contact

Discharging an electroscope by contact is demonstrated.

Discussion

A somewhat simplified explanation of why, when the demonstrator touches a charged electroscope, the electroscope is discharged is this: If the excess charge on the electroscope is positive, mobile electrons on the demonstrator will move from the demonstrator to the electroscope, attracted by the positive charge, until it is essentially neutral; if the excess charge is negative, mobile electrons, repelled by the negative charge, will move from the electroscope to the demonstrator until the electroscope is again essentially neutral. Although at the end of this process the excess charge has not been neutralized, it is now distributed over the surface of the small post and leaves of the electroscope and the surface of the large demonstrator, with most of it on the larger demonstrator and only a small, undetectable amount on the electroscope.