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Charles-Augustin de Coulomb Created 2026-10-24 Updated 2026-11-05
Charles-Augustin de Coulomb used a torsion balance to turn weak electric forces into measurable angular displacements. The restoring torque of a twisted silver wire supplies a calibrated mechanical comparison with the electric force. In his first electrical memoir for 1785, he varied the wire's imposed twist and compared the equilibrium separations of two small bodies carrying like electric charges. The total twist, including the moving arm's deflection, determines the restoring torque. These measurements supported the inverse-square dependence expressed by Coulomb's law, joining a mechanical calibration with the geometry of electric charges.[ref]
Premier mémoire sur l'électricité et le magnétisme by Charles-Augustin de Coulomb. First memoir, apparatus construction, repulsion trials and total torsion-angle comparison, pp. 569–577; Academy volume for 1785, printed 1788
Physicist and engineer whose work includes friction and strength of materials. His name appears in the Mohr-Coulomb failure criterion.
Portrait of Charles-Augustin de Coulomb
. Louis Hierle, 1894, after Hippolyte Lecomte; painted portrait at Versailles. Public domain according to the Wikimedia Commons file page (PD-old-100 and PD-US-expired). Source usage terms, via Wikimedia Commons. Source.