André Marie Ampère

Born Jan. 22, 1775, in Lyons; died June 10, 1836, in Marseilles. French physicist and mathematician; one of the founders of electrodynamics (now commonly referred to as electromagnetism), member of the Academy of Sciences of Paris (1814).

Ampère was born into an aristocratic family. Having read all 20 volumes of the Encyclopédie of D. Diderot and J. L. d’Alembert by the age of 14, Ampère devoted himself entirely to the study of the natural sciences and mathematics. In 1801 he occupied the chair in physics at the Ecole Centrale in Bourg-en-Bresse and in 1805 obtained the position of academic coach at the Ecole Polytechnique in Paris. During this period he published his works on the theory of probability and on the application of the calculus of variations to problems of mechanics, as well as a number of research papers on mathematical analysis. From 1824 he was professor at the Ecole Normale in Paris.

Ampère’s works in the field of physics have ranked him among the world’s most outstanding scientists. After H. C. Oersted discovered the effect of an electric current on a magnetic needle in 1820, Ampère proposed the “swimmer’s rule” for determining the direction in which the current causes the magnetic needle to deviate. Further research led Ampère to discover the mechanical interaction of electrical currents and establish the quantitative ratios for determining the force of this interaction (Ampère’s law). Ampère formulated the first theory of magnetism based on the hypothesis of molecular currents, according to which the magnetic properties of a substance are determined by the electrical currents circulating in the molecules. Ampère’s theory of magnetism laid to rest the theories of a “magnetic fluid” as a special carrier of magnetic properties and was the precursor of the electron theory of magnetism; after Ampère, magnetism became part of electrodynamics. Ampère’s electrodynamic theory is set forth in his book The Theory of Electrodynamic Phenomena Based Exclusively on Experiment (1826). At the end of his life Ampère worked out a classification system of the science of his time, which he set forth in his work An Essay on the Philosophy of Sciences (1834).