Faraday's ice pail: Charge induced on the outside of a pail.

Faraday's ice pail: Charge induced on the outside of a pail. Thick Glass Plate on Sealing Wax Faraday's Ice Pail (Copper Cup) The distribution of charge over a metal conductor can be demonstrated by Faraday's Ice Pail. A metal sphere is electrostatically charged. (The Wimshurst machine gives a good charge. The electrophorous works less well. See D+10+18-22). Say the sphere is charged negatively. The metal sphere is then lowered into a metal cup, without actually touching the sides of the cup. Free electrons in the metal pail are repelled to the to the outer surface. The net charge on the outer surface is negative, and the electroscope leaf rises. The charge on the inner surface of the cup is positive. If the ball is now removed, the electroscope leaf falls, and the pail is uncharged. If, however, the ball touches the pail, all negatives leave the ball and neutralize an equal number of pail positives. The electroscope leaf remains fixed in its raised position, showing there is no redistribution of the negative charges on the outer pail surface; and also the number of induced positive charges within the pail equals the number of negative charges on the ball. Reference: The below was paraphrased from MODERN COLLEGE PHYSICS, p.343 by Harvey E. White, 6th edition