A superconductor is a substance that conducts electricity without resistance when below a critical temperature. At this temperature electrons can move freely through the lattice. High magnetic fields destroy superconductivity and restore the normal conducting state.
We expect a magnet moving by a conductor to induce a currents in the conductor by electromagnetic induction. But, a superconductor expels magnetic fields by inducing surface currents. The Meissner effect is demonstrated by levitating a superconductor over magnets or vice versa.
History of superconductors[change | change source]
|1911||superconductivity discovered by Heike Kamerlingh Onnes|
|1933||the Meissner effect discovered by Walter Meissner and Robert Ochsenfeld|
|1957||theoretical explanation for superconductivity put forward by John Bardeen, Leon Cooper, and John Schrieffer (BCS theory)|
|1962||the tunneling of superconducting Cooper pairs through insulating barrier predicted|
|1986||A ceramic superconductor was discovered by Alex Müller and Georg Bednorz. Ceramics are normally insulators. A lanthanum, barium, copper and oxygen compound with a critical temperature of 30K. Opened up the possibilities for new superconductors.|
Applications[change | change source]
- Superconducting quantum interference device (SQUID)
- Particle accelerators
- Small particle accelerators in health
- Levitating trains
- Nuclear fusion
- MRI Scanner