# Coulomb, Charles Augustin

### From Enlightenment Revolution

**Coulomb, Charles Augustin** (1736-1806): French, Physicist.

Coulomb is remembered for formulating basic quantitative laws of electrostatics and magnetism. He quantified the effects of electromagnetism on the motion of charged objects.

Coulomb’s Law defines the properties of electric force for charges at rest: like charges repel each other, opposite charges attract; the size of the force varies inversely to the square of the distance and is proportional to the value of each charge. Modern physics refer to the unit of electricity representing the quantity transported in one second by a current of one ampere as a coulomb (C) Furthermore Coulomb invented the torsion balance, an instrument for accurate measurement of forces of electric and magnetic attraction, used in electrical experiments throughout the nineteenth century. He also made important contributions to engineering; the Coulomb equation and his earth pressure theory are still included in textbooks on soil mechanics.

Charles Augustin Coulomb was born in Angoulême. His family moved often. He lived in Paris in the late 40s, in Montpellier in the late 50s. He early exhibited an interest in mathematics and in 1760 enrolled in the School of Military Engineering in Mézières. As a graduate he was sent to the West Indies where he spent nine years building fortifications. His work here in applied mechanics and engineering strongly influenced his later studies in physics. Upon his return to France he continued to make major contributions to the corps of engineers, while also pursuing research and presenting a series of papers .The most important of his early papers was his 1773 “Memoir on Statics,” which illustrates his innovative investigative method. Rather than simply describe experiments, as had been the custom, Coulomb backed his theories and experiments with mathematical proof; thus he transformed Priestley, Joseph’s descriptive observations into quantitative laws.

In his later *Theory of Simple Machines* (1777), he established formulae for calculating the effects of friction. In the same year, he published his first highly acclaimed memoir on magnetism, in which, by using his newly invented torsion balance, he was able to suggest remedies for problems with the magnetic compass.

In 1781 he left the Army, settled in Paris, was elected to the Academy of Sciences, and thereafter dedicated himself almost exclusively to research, as he was now well recognized as a scientist, had access to books and equipment and to stimulating discussions with fellow academicians. His career blossomed at the very time when the ferment of the Enlightenment transformed physics into an independently recognized discipline and led it to branch out into new fields like heat, light, and electricity.

There was a pause in Coulomb’s public life during the Revolution when he retired to his modest estate in Blois, but his research continued uninterrupted. He produced seven major works on electricity and magnetism between 1785 and 1791. In 1802, he returned to Paris to assist the government in devising a uniform national metric system of weights and measures.

Further Reading:

Stewart C. Gillmor, *Coulomb and the Evolution of Physics and Engineering in Eighteenth Century France*, 1971

**Natalie Sandomirsky**

Southern Connecticut State University