born June 14, 1736, Angoulême, France
died Aug. 23, 1806, Paris
French physicist.
After serving as a military engineer in the West Indies, he returned to France in the 1780s to pursue scientific research. To investigate Joseph Priestley 's law of electrical repulsions, he invented a sensitive instrument to measure the electrical forces involved. A light rod made of an insulator, with a small conducting sphere at each end, was suspended horizontally by a fine wire so that it was free to twist when another charged sphere was brought close to it. By measuring the angle through which the rod twisted, Coulomb could measure the repulsive forces. He is best known for formulating Coulomb's law . He also did research on friction of machinery, on windmills, and on the elasticity of metal and silk fibres. The coulomb, a unit of electric charge, was named in his honour.