Electromagnet is a temporary magnet formed when electric current flows through a wire or other conductor. Most electromagnets consist of wire wound around an iron core. This core is made from magnetically soft iron. The iron loses its magnetism quickly when the electric current stops flowing through the wire. Changing the current can also vary the magnet’s strength.
Electromagnets drive loudspeakers, electric doorbells, buzzers, and relays. They are used in magnetic resonance imaging (MRI) machines, particle accelerators, and other scientific equipment. They also produce the magnetic fields needed to make electric motors and generators work. Powerful industrial electromagnets lift heavy pieces of scrap iron.
In 1820, Danish physicist Hans Oersted discovered that an electric current produces a magnetic field. In 1825, English electrician William Sturgeon showed that an iron core strengthens a coil’s magnetic field. American physicist Joseph Henry built the first practical electromagnet in the late 1820’s.
See also Electromagnetism; Henry, Joseph; Linear electric motor; Superconductivity; Plasma.
