A superconductor is a substance which conducts an electric current with zero resistance. It also repels magnetic fields perfectly at a certain point which is also known as the Meissner effect.

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What is a Superconductor?

A superconductor is a substance which conducts an electric current with zero resistance. It also repels magnetic fields perfectly at a certain point which is also known as the Meissner effect. This effect can cause certain superconductors to float endlessly above a strong magnetic field. Materials which are said to be superconductive include: some semiconductors, certain types of ceramics and metals and their alloys eg. tin, aluminium.

Superconductors are one of the last greatest scientific discovery, not only because the limits of superconductivity have not yet been reached, but the theories that explain superconductor behavior have also been under review.

The History of Superconductors

In 1911, superconductivity was first discovered in mercury by Dutch physicist Heike Kamerlingh Onnes of Leiden University. He was cooling the mercury and when he cooled it to the temperature of liquid helium, 4 degree Kelvin, the resistance suddenly disappeared. Onnes then won a Nobel Price in physics in 1913 for his research in this area. Later on in 1933, German researchers Walther Meissner and Robery Ochsenfeld discovered the Meissner effect (also known as the Meissner-Ochsenfeld effect). It is the effect by which a weak magnetic field decays rapidly to zero in the interior of a superconductor. They discovered it by examining the magnetic properties of materials as they became superconductive. The Meissner effect is now used as a routine test for superconductivity.

During 1941 -1953, niobium-nitride and vanadum-silicon were found to superconduct at 16 degrees Kelvin and 17.5 degrees Kelvin respectively. In 1962, scientists at Westinghouse developed the first commercial superconducting wire with an alloy of niobium and titanum (NbTi). The first widely accepted theoretical explanation of superconductivity, now known as the BCS theory, was created in 1957 by American physicists John Bardeen, Leon Cooper, and John Schrieffer. They then won a Nobel prize in 1972. The BCS theory explained superconductivity at temperatures close to absolute zero for elements and alloys. However, this theory didn't success in explaining how superconductivity occurs in higher temperatures.

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The BCS Theory: The molecular vibrations in the lattice slow down when the temperature goes down, bellow the critical temperature this lack of movement allows the flow of electrons without any obstacle which translates in superconductivity. An interesting factor of this theory is the appearance of Cooper pairs (the electrons move coupled in pairs).

In the early 1960s at the Rutherford-Appleton Laboratory in the UK, high-energy and particle accelerator electromagnets made of copper-clad niobium-titanium were then developed. They were also first employed in a superconducting accelerator at the Fermilab Tevatron in the US in 1987.

Brian D. ...

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