\ˈœ̅r-stet͟h, -stəd; ˈə(r)-stəd\, Hans Christian (1777–1851),
Danish physicist. Oersted was a professor of physics at the University of Copenhagen, and in 1820 he reported his discovery that a compass needle—a magnet—moved to a position at right angles to the direction of an electric current. This discovery established that a relationship exists between electricity and magnetism, and it marked the foundation of the science of electromagnetism, to which Ampère and Faraday later made significant contributions. The cgs unit of magnetic field strength was named in Oersted's honor.