A diagram of the Meissner Effect with magnetic field lines, represented as arrows, excluded from a superconductor when it is cooled to below its critical temperature (the temperature at which it loses all resistance to the flow of electrical current).
A magnet levitating above a superconductor (cooled by liquid nitrogen).
Superconductivity was discovered in 1911 by the Dutch physicist, Heike Kammerlingh Onnes when he was able to liquefy helium by cooling it to 4 Kelvin, or -452°F. This enabled him to cool other materials close to absolute zero and investigate their electrical properties.
He noted that at these cold temperatures certain materials would lose all resistance to the flow of electrons and become essentially perfect conductors of electricity. He called this newly discovered state Superconductivity. An electrical conductor with no resistive heating can carry current any distance with no losses, giving it essentially 100% efficiency. Once direct current is introduced into a superconducting loop, it can flow undiminished forever.
The discovery in 1986 by Georg Bednorz and Alex Müller, working at IBM in Zurich, Switzerland, of ceramic-based materials that could achieve the state of superconductivity at relatively higher temperatures opened the possibility of applying this technology to electric power devices such as transmission cable, transformers, motors and generators. These materials are called High Temperature Superconductors (HTS) and can achieve their critical temperature (77K) using inexpensive liquid nitrogen, rather than the more expensive liquid helium required by the original, 'Low' Temperature Superconductors (LTS) which are commonly used in the superconducting magnets that power Magnetic Resonance Imaging (MRI) systems. The reduced cooling needs of HTS offer performance advantages to electric power devices that do not exist with LTS.
Commercial applications of Superconductors:
Energy: generators, transformers, underground cables, synchronous condensers, fault current limiters, industrial motors, magnetic energy storage Transportation: ship propulsion systems, magnetically levitated trains, railway traction transformers, electric vehicle motors Healthcare: magnetic resonance imaging [MRI], particle beam therapy Industry: magnetic separatiors, large motors and generators, magnetic billet heaters Communications: HTS filters for cellular communications systems Science & Research: accelerator magnets, other high field magnets Military: airborne generator, ship propulsion, directed energy weapons, degaussing cables