Oersted, Hans Christian (1777–1851)

Danish physicist who founded the science of electromagnetism. In 1820 he discovered the magnetic field associated with an electric current. In 1825 he was the first to isolate aluminium.

Oersted was born at Rudkøbing, Langeland, and studied at Copenhagen. He worked as a pharmacist before making a tour of Europe 1801–03 to complete his studies in science. On his return, Oersted gave public lectures with great success, and was professor of physics at Copenhagen 1806–29, when he became director of the Polytechnic Institute in Copenhagen.

Believing that all forces must be interconvertible, Oersted had predicted in 1813 that an electric current would produce magnetism when it flowed through a wire, just as it produced heat and light. His 1820 experiment involved a compass needle placed beneath a wire connected to a battery. He found that a circular magnetic field is produced around a wire carrying a current.

In 1822 Oersted turned to the compressibility of gases and liquids, devising a useful apparatus to determine compressibility. He also investigated thermoelectricity, in 1823.