André-Marie Ampère

Library of Congress

[b. Lyon, France, January 20, 1775, d. Marseilles, France, June 10, 1836]

Ampère was the first to recognize that there is a direction for the flow of an electric current and to introduce a convention for determining that direction. He showed that wires carrying electric currents attract and repel each other magnetically. The amount of magnetism reflects the strength of the current. In 1827 he put his discoveries into the mathematical form known as Ampère's law: The magnetic force generated between two current-carrying wires varies directly with the product of their currents and inversely with the square of the distance between the wires. Ampère was one of the first to show that when current flows through a wire coiled into a helix, or three-dimensional spiral, the wire behaves like a bar magnet. This property later fueled many of the inventions of the age of electricity, including the telegraph, electric motor, and telephone.

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Ampère, André-Marie (1775-1836). French physicist, founder of the science now known as electromagnetism. Ampère, a child prodigy in mathematics and later an inspired experimentalist, was the first to demonstrate, and to express mathematically, the relationship between electricity and magnetism. He initiated a standard system of measurement for electric currents. His works include an Essai sur la philosophie des sciences (1834-44) and the posthumously published Journal et correspondance.

[Malcolm Bowie]

(ăm'pēr; Fr. äNdrā' märē' äNpĕr') , 1775–1836, French physicist, mathematician, and natural philosopher. He was professor of mathematics at the École Polytechnique, Paris, and later at the Collège de France. Known for his contributions to electrodynamics, including the formulation of Ampère's law, he confirmed and amplified the work of Oersted on the relationship of electricity and magnetism, and he invented the astatic needle. The ampere was named for him. His writings include Recueil d'observations électro-dynamiques (1822) and Essai sur la philosophie des sciences (2 vol., 1834–43, vol. 1 repr. 1838).

Bibliography

See his Correspondance pub. by L. de Launay (3 vol., 1936–43).

French physicist and mathematician who formulated Ampère's law, a mathematical description of the magnetic field produced by a current-carrying conductor.