Charles Augustin de Coulomb

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Charles Augustin de Coulomb

The French physicist Charles Augustin de Coulomb (1736-1806) was famous for establishing the relation for computing the force between electrical charges. He also did pioneering work on sliding and fluid friction.

Charles Augustin de Coulomb was born into a distinguished family of Angoulême on June 14, 1736. After being educated in Paris, he spent 9 years in Martinique as an army engineer. Ill health forced him to return to France in 1776, where during the next 13 years his scientific work brought him fame, military advancement, and membership in the Royal Academy of Sciences. He was appointed intendant of France's waters and fountains in 1784. The next 5 years were spent in writing his memoirs on electricity and magnetism. Coulomb had become a noted and influential figure in the academic world but resigned all his positions at the outbreak of the Revolution. He returned to Paris in 1802 for an appointment as one of the inspector generals of public instruction.

Coulomb's 1779 memoir, The Theory of Simple Machines, is a compilation of his early experiments on statics and mechanics in which he makes the first formal statement of the laws governing friction. In 1784 he studied torsional elasticity, finding the relationship between the various factors involved in the small oscillations of a body subjected to torsion.

His most notable papers are the seven which Coulomb presented before the academy in 1785 and 1786. In the first he announced the measurement of the electrical forces of repulsion between electrical charges. He extended this work to the forces of attraction in his second memoir. This led to further quantitative work and his famous law of force for electrostatic charges (Coulomb's law). The subsequent papers dealt with the loss of electricity of bodies and the distribution of electricity on conductors. He introduced the "proof plane" and by using it was able to demonstrate the relationship between charge density and the curvature of a conducting surface.

Magnetism was the subject of Coulomb's early studies and the one to which he returned in later years. He noted that magnetism obeyed a relation of attraction and repulsion similar to that for electrical forces. He also established the equation of motion of a magnet in a magnetic field, showing the derivation of the magnetic moment from the period of small oscillations.

In 1801 Coulomb published another important paper, in which he presented the results he obtained by allowing a cylinder to oscillate in a liquid, thus providing a way to find relative liquid viscosities.

Of Coulomb, Thomas Young wrote, "his moral character is said to have been as correct as his mathematical investigations." He remained in Paris until his death on Aug. 23, 1806.

Further Reading

Most of the information on Coulomb is in French. In English, descriptions of his experiments are in William Francis Magie, A Source Book in Physics (1935); Duane Roller and Duane H. D. Roller, The Development of the Concept of Electric Charge: Electricity from the Greeks to Coulomb (1954); and Morris H. Shamos, ed., Great Experiments in Physics (1960). For general background on the scientific environment of the time see Abraham Wolf, A History of Science, Technology and Philosophy in the Eighteenth Century (1939). Brief references also appear in A History of the Theories of Aether and Electricity: From the Age of Descartes to the Close of the Nineteenth Century (1910), and Hugh Hildreth Skilling, Exploring Electricity: Man's Unfinished Quest (1948). □

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Charles Augustin de Coulomb

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