COULOMB, CHARLES AUGUSTIN (1736-1806), French physicist, was born in Angouleme on June 14, 1736. He was a military engineer, and after spending nine years in the West Indies he returned to France with his health much impaired. In 1789, on the outbreak of the Revolution, he retired to a small estate at Blois and devoted himself to scientific research. In 1802 he was appointed an inspector of public instruction; he died in Paris on Aug. 23, 1806.
Coulomb designed the torsion balance independently of Michell in 1777. He published papers on friction as applied to machinery (1779) ; on windmills (1781), and on the torsional elasticity of metal and silk fibres (1784). His electrical papers were published in the Memoirs de l'Academie royale des sciences between 1785 and 1789; these formed the basis of the mathematical theory of electricity of Poisson. The first three memoirs appeared in 1785, the following numbers in 1786, 1787, 1788 and 1789. In these memoirs Coulomb gave an account of his work with the torsion balance in verifying Priestley's law of electrical repulsions. He extended the case to include attractions and finally stated that the force is proportional to the product of the charges and in versely proportional to the square of the distance between them. He also verified the inverse square law for particles of magnetic fluid; he believed in the two-fluid theory, but assumed that the magnetic fluids could not be separated but that the electric fluids were separable. In the fourth memoir Coulomb showed that an electric charge is confined to the surface of a conductor and he compared the distribution of charge on the surface of conductors. He virtually established the result that the electric force near a ._onductor is proportional to the surface density of electrification (this was later proved by Poisson) ; he also stated that in the case of action at a distance the intervening medium played no part. Cavendish had anticipated Coulomb in the statement of the inverse square law, but this work was unpublished until many years after his death.