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Charles Augustin de Coulomb (June 14, 1736 – August 23, 1806) was a French physicist.
Coulomb was born in Angoulême, France, son of Henry Coulomb, inspector of the Royal Fields in Montpellier, and Catherine Bajet. He studied in the Collège des Quatre-Nations in Paris although strictly speaking its family did not belong to the aristocracy. The courses of mathematics of Pierre Charles Monnier decided him to abandon medicine. He joined his father's family in Montpellier and take part from 1757 to 1759 in the work of the academy of this city, directed by the mathematician Augustin Danyzy. With his father approval, it returns to Paris in 1759 to attend the courses of the preparatory institute directed by abbot Camus, and make a success of the entrance examination at the military school at Mézières.
At his exit from the school in 1761, he initially took part in the survey for the British coastal charts, then was sent on mission to Martinique in 1764 to take part in the construction of the Fort Bourbon under the orders of the lieutenant-colonel of Rochemore, as the French colony is insulated in the middle of the English and Spanish possessions following the Seven Year old War. Coulomb works ther eight years directing the work, contracts tropical fever, but carries out also several experiments on the resistance of masonries and the behaviour of the walls of escarpe (supportings), which were inspired by the ideas of Pieter van Musschenbroek on friction.
Upon his return, with the rank of Captain, he was employed at La Rochelle, the Isle of Aix and Cherbourg. He discovered an inverse relationship on the force between electric charges and the square of its distance, later named after him as Coulomb's law.
In 1781, he was stationed permanently at Paris. On the outbreak of the Revolution in 1789, he resigned his appointment as intendant des eaux et fontaines, and retired to a small estate which he possessed at Blois. He was recalled to Paris for a time in order to take part in the new determination of weights and measures, which had been decreed by the Revolutionary government. Of the National Institute he was one of the first members; and he was appointed inspector of public instruction in 1802. But his health was already very feeble, and four years later he died in Paris.
Coulomb is distinguished in the history of mechanics and of electricity and magnetism. In 1779 he published an important investigation of the laws of friction (Théorie des machines simples, en ayant égard au frottement de leurs parties et à la roideur des cordages), which was followed twenty years later by a memoir on viscosity.
In 1784 his Recherches théoriques et expérimentales sur la force de torsion et sur l'élasticité des fils de metal (Histoire de l’Académie Royale des Sciences, 229-269, 1784) appeared. This memoir contained a description of different forms of his torsion balance. He used the instrument with great success for the experimental investigation of the distribution of charge on surfaces, of the laws of electrical and magnetic force, and of the mathematical theory of which he may also be regarded as the founder.
In 1785 Coulomb presented his three reports on Electricity and Magnetism:
- Premier Mémoire sur l’Electricité et le Magnétisme, Histoire de l’Académie Royale des Sciences, 569-577, 1785. In this publication Coulomb describes “How to construct and use an electric balance (torsion balance) based on the property of the metal wires of having a reaction torsion force proportional to the torsion angle”. Coulomb also determinates experimentally the law that explains how “two bodies electrified of the same kind of Electricity exert on each other”.
- Sécond Mémoire sur l’Electricité et le Magnétisme, Histoire de l’Académie Royale des Sciences, 578-611, 1785. In this publication Coulomb carries out the “determination according to which laws both the Magnetic and the Electric fluids act, either by repulsion or by attraction”.
- Troisième Mémoire sur l’Electricité et le Magnétisme, Histoire de l’Académie Royale des Sciences, 612-638, 1785. “On the quantity of Electricity that an isolated body losses in a certain time period , either by contact with less humid air, or in the supports more or less idio-electric”.
Coulomb explained the laws of attraction and repulsion between electric charges and magnetic poles, although he did not find any relationship between the two phenomena. He thought that the attraction and repulsion were due to different kinds of fluids.
The SI unit of charge, the coulomb, and Coulomb's law are named after him.
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