Franz Aepinus (13.12.1724-22.08.1802) was a physicist and a member of the St Petersburg Academy of Sciences (1756). He was born in Rostock (Germany). He studied at the universities of Rostock and Jena. For some time he worked at the universities of Rostock and Berlin. In 1757 — 98 he was professor of physics at the St Petersburg Academy of Sciences.
His work concerned the study of electrical and magnetic phenomena and optics. He discovered pyroelectricity in tourmaline crystals (1756). In the treatise “An Essay on the Theory of Electricity and Magnetism” (1759) he worked out the first mathematical theory of electrical and magnetic phenomena. Following B. Franklin, he based his theory on the idea of electric and magnetic “fluids”, an excess or deficiency of which leads to the electrification or magnetisation of bodies, and proceeding from this he explained electrostatic and magnetic induction. He put forward the idea (1759) that electric and magnetic forces, like the forces of gravitation, are inversely proportional to the square of the distance. He came close to the concepts of capacitance and potential, and put forward (1757) the idea of the electrophorus.