(1736-1806) French Theoretician and Experimentalist (Electromagnetism, Electrostatics, Mechanics)
Charles Augustin Coulomb pioneered the science of electrostatics and established the laws governing electric charges. In recognition of his achievement the unit of electric charge is named the coulomb.
He was born on June 14, 1736, in Angouleme, in southwestern France, into a wealthy family, active in legal and governmental circles. When Charles was a boy, the family moved to Paris, where he received a solid grounding in both the sciences and the humanities at the College Mazarin. He then entered the Engineering School in Mezieres and graduated in 1761 as a military engineer with the rank of first lieutenant in the engineering corps.
Over the next 20 years he traveled extensively with the corps, working on projects involving engineering, structural design, fortifications, and soil mechanics. He spent eight years (1764-1772) on Martinique in the West Indies, when the island was attacked by both British and Dutch fleets, and took charge of building a new fort.
In 1773, he returned to France, to Bouchain, where he began to write important work on applied mechanics. In the first paper he delivered before the Academie des Sciences in Paris, he discussed the influence of friction and cohesion in problems of statics. At his next posting, in Cherbourg, he wrote a famous paper on the magnetic compass, which contained his first work on the torsion balance, a device he invented for measuring very small forces by the torsion (twist) they cause in a fiber or a wire. He was the first to show physicists how the torsion suspension could provide a method of accurately measuring extremely small forces. Sent to Rochefort in 1779, he continued his study of mechanics, using Rochefort’s shipyards as laboratories for his experiments. He wrote a major work on friction, The Theory of Simple Machines, which won him the Grand Prix from the Academie des Sciences in 1781. In this classic work he virtually created the science of friction, extending knowledge of the effects of friction caused by factors such as lubrication and differences in materials and loads.
The recognition Coulomb received for this work enabled him to leave engineering projects behind him and to devote himself to physics. He was elected to the mechanics section of the Academie and moved to Paris, where he obtained a permanent position. Between 1785 and 1791, Coulomb wrote seven important treatises on electricity and magnetism and submitted them to the academie. In these treatises, influenced by the work of Joseph Priestley on electrical repulsion, he developed a theory of attraction and repulsion: that bodies with the same electrical charge repel each other, whereas bodies with opposite electrical charge attract each other. He examined perfect conductors and insulators (dielectrics) and concluded that a perfect dielectric does not exist in nature, since, above a certain limit, every substance conducts electricity. He treated the electrical force in a manner similar to the way sir isaac newton treated gravitational force, that is, as an action at a distance. Coulomb’s major contribution was in electrostatics, the study of time-independent electric fields, in which he made extensive use of an adapted version of his torsion balance. Coulomb performed his experiment by using certain reasonable assumptions, namely, (1) that the electrical forces behave as if concentrated on a point and (2) that the dimensions of the bodies are small compared with the distance between them. Under these conditions he found that the force between two electric charges on these bodies was proportional to the product of the charges and inversely proportional to the square of the distance between their centers; this relationship became known as Coulomb’s law. Coulomb also investigated the distribution of electric charge over a body and found that it is located only on the surface of the charged body and not in its interior.
In other work, Coulomb demonstrated the inverse square law of repulsion and attraction in like and unlike magnetic poles. He wrote a total 25 papers between 1781 and 1806, working closely with other eminent scientists of the time. His life was also filled with the preparation of hundreds of committee reports for the academie, with his engineering consulting, and with his multifaceted service to the French government. At different times, Coulomb found himself in charge of the education in public schools, hospital reform, care of the royal fountains, and administration of the water supply of Paris. From 1802 to 1806, as inspector general of public education, he was mainly responsible for setting up lycees (secondary schools) throughout France.
When, in 1789, the French Revolution led to the reorganization of many institutions, Coulomb retired from the engineering corps, and he withdrew to his country home to continue his research in 1791. He would return to Paris a few years later, when the abolished Academie des Sciences was replaced by the Institut de France in 1795. Coulomb became its president in 1801. The following year, he married Louise Frangoise LeProust Desormais, who had already borne him two sons. Four years later, on August 23, 1806, at the age of 70, he died in Paris.
Coulomb’s work established electrostatics as an exact science. A century later Coulomb’s law would become an important component of the unified theory of electrodynamics developed by james clerk maxwell.
