Electromagnetism

Electromagnetism, in physics, relation between electricity and magnetism based on the facts that electric currents produce magnetic fields and magnetic fields produce electric fields. These discoveries were made in the 1820s by physicists Hans Oersted (Denmark) and André Marie Ampère (France), working independently. Their work led to the development of the electromagnet, the basis of the electric motor, the telephone, and the loudspeaker, among other devices. Electromagnetic induction is the production of an electric current as a conductor moves in a magnetic field, or is situated in a magnetic field that is changing in strength. This effect was discovered by physicists Michael Faraday (England) and Joseph Henry (U.S.) in 1831, again independently. It is the basis of the electric generator and the transformer.