Static Electricity

Author: E.E. Kimberly

When glass is rubbed with silk in the classical experiment in physics, some of the electrons in atoms in the glass are induced to move over to the silk and so leave more protons than electrons in the rod. The rod then exhibits a positive charge, and the silk has a negative charge. Such charges are called static charges because they "stand on" or inhabit the bodies which exhibit the charges. Such manifestations have few uses in engineering and, indeed, are likely to be troublesome. Static charges appear on sheets of paper passing through a printing press and cause the sheets to cling to each other and to the press. They appear on the uniforms of nurses in hospital operating rooms and, by their discharge, explode vapors of anaesthetics which may be present. They appear on rapidly moving power-transmission belts and may produce sparks several feet long.

Probably the most useful application is that of removing dust, smoke, and vapor particles by precipitation from gases, from air in particular. The particles in passage through the precipitator are given a charge, which is usually positive, and are then caused to flow near plates or screens of opposite charge to which they are attracted. The plates or screens are shaken down periodically, and the residue is removed. No "static machine" is used, however, for these industrial applications. Instead, high-voltage electron tubes described in a subsequent chapter are used to obtain high potentials.