Coulomb, Charles Augustin de (1736–1806)

French scientist, inventor of the torsion balance for measuring the force of electric and magnetic attraction. The coulomb was named after him. In the fields of structural engineering and friction, Coulomb greatly influenced and helped to develop engineering in the 19th century.

Coulomb's law of 1787 states that the force between two electric charges is proportional to the product of the charges and inversely proportional to the square of the distance between them.

Coulomb was born in Angoulême and trained as a military engineer. He was posted to Martinique to undertake construction work 1764–72. From 1781 he was in Paris, resigning from the army during the French Revolution.

Coulomb took full advantage of his various postings to pursue a variety of studies, including structural mechanics, friction in machinery, and the elasticity of metal and silk fibres. In his 1781 study of friction, he extended knowledge of the effects of friction caused by such factors as lubrication and differences in materials and loads, producing a classic work that was not surpassed for 150 years. He also carried out fundamental research in ergonomics.

The torsion balance Coulomb invented is described in a paper of 1777, and in a paper of 1785 he discussed its adaptation for electrical studies. He went on to investigate the distribution of electric charge over a body and found that it is located only on the surface of a charged body and not in its interior.