Superconductivity

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Superconductivity
For Physics 3h students

• Basic properties
• What is it good for? (applications)

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What is a superconductor?

• Well, this is a material with no resistance
• It can not be used for heating!

It can however be used to conduct electricity
with no losses
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Basic properties - 1

• The resistance of a metal drops to zero under a
  certain transition temperature called Tc.
• This is true as long as the current through the
  metal does not exceed a critical value called Ic.

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Basic properties - 2

• The Meissner effect
• A magnetic field penetrates a normal metal
  uniformly
• The field is expelled from the metal when it
  becomes superconducting for TltTc

Above a critical field Hc the material becomes
normal again
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Basic properties - 3

• What is the mechanism of superconductivity?
• creation of electron pairs Cooper pairs via
  phonon attraction
• A superconductor posses a macroscopic
  wave-function which exists all over the material
• ?(r) ?o exp-i?

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Some superconductor applications

• Eliminate losses in electricity grids
• Produce excellent filters for cellular
  communication
• Used for magnetic levitation of trains MAGLEV
• Used for magnetic energy storage SMES
• Used as current fault limiters recoverable
  fuse
• MRI - magnetic resonance imaging magnets

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Typical HTS filter response