Electric Currents, Magnetic Forces

Abstract

André Marie Ampère (1775–1836) was born in Lyon, France. He was home-schooled by his father, a merchant who directed his education and was guillotined in 1793 during the Jacobin purges of the French revolution. Ampère taught himself latin and mathematics at an early age in order to understand the scientific and mathematical writings of Euler and Bernoulli. He began his academic career as a mathematics teacher in 1799. He was appointed professor of physics and chemistry in 1802 at the École Centrale at Bourg, professor of analysis in 1809 at the École Polytechnique in Paris, and chair of experimental physics at the Collège de France in 1824. Like many other prominent figures of the French enlightenment, Ampère’s academic interests were quite broad, including astronomy, chemistry, mathematics and philosophy. Inspired by Oersted’s recent discovery of the effect of an electric current on a magnetized compass needle, Ampère performed a number of careful experiments on the relationship between electricity and magnetism; the mathematical formulation of his results came to be known as Ampère’s law. The text that follows is comprised of two extracts. The first is from a paper entitled “Experiments on the New Electrodynamical Phenomena,” In it, Ampère introduces some new terminology. The second is from a memoir presented before the Academy of Sciences on October 2, 1820. It describes his experiments on the force acting between two parallel electrical currents.

The attractions and repulsions which occur between two parallel currents, according as they are directed in the same sense or in opposite senses, are facts given by an experiment which is easy to repeat.

—André Marie Ampère