Charles Coulomb

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FRENCH ENGINEER AND PHYSICIST
1736–1806

Charles-Augustin de Coulomb was born to affluent parents in Angoulême, France. His father's family was prominent in the legal profession and involved in the administration of the Languedoc region of France. His mother's family was quite wealthy. After being raised in Angoulême, Charles moved with his family to Paris, where he entered the Collège Mazarin and pursued a classical education.

After a brief stay in Montpellier, Coulomb returned to Paris to study at the École du Génie at Mézières. This was one of the first schools of engineering; it specifically focused on military engineering. Coulomb graduated in 1761 with a degree in engineering and the rank of lieutenant in the Corps du Génie. Over the next twenty years, he was posted to a variety of locations where he became involved in the structural design of forts and fortifications, and soil mechanics.

In 1777 his work on torsion balances (among other subjects) won Coulomb a share of the Grand Prix of the Académie des Sciences. Historically, all measurements of weight had been obtained by using a two-pan balance, which is simply a bar centered on a fulcrum . Coulomb's torsion balance replaced the fulcrum with a fine silk thread or hair, and rather than the up-and-down motion of the pan balance, he used a twist or torsion around this thread. He was able to show that the amount of torsion is proportional to the amount of force; thus he devised a method for measuring very small interactions.

With his very fine torsion balance, Coulomb was able to demonstrate that the repulsive force between two small spheres electrified with the same type of electricity is inversely proportional to the square of the distance between the centers of the two spheres. At the time, the electron had not yet been discovered, so the underlying reason for this remained a mystery but Coulomb was able to demonstrate that both repulsion and attraction followed this principle. He was not able to make the quantitative step to show that the force was also directly proportional to the product of the charges, but he did complete some experiments exploring this relationship. As a consequence, the law governing one of the four fundamental forces of nature is named Coulomb's law:

F = kq ₁ q ₂ / r ²

For his work in setting physics on a course of discovery, the fundamental unit of charge was named the "coulomb" in his honor.

SEE ALSO Bonding .

Todd W. Whitcombe

Bibliography

Gillmor, C. S. (1971). Coulomb and the Evolution of Physics and Engineering in Eighteenth Century France. Princeton, NJ: Princeton University Press.

Internet Resources

Katz, E. "Charles-Augustin de Coulomb." Available from http://www.geocities.com/bioelectrochemistry/coulomb.htm .