section_path: Superfluids and condensates/Superconductor
section_name: Superconductor
paragraph_text: Superconductor
  
  Superconductors are materials which have zero electrical resistivity, and therefore perfect conductivity. This is a distinct physical state which exists at low temperature, and the resistivity increases discontinuously to a finite value at a sharply-defined transition temperature for each superconductor.
  
  A superconductor also excludes all magnetic fields from its interior, a phenomenon known as the Meissner effect or perfect diamagnetism. Superconducting magnets are used as electromagnets in magnetic resonance imaging machines.
  
  The phenomenon of superconductivity was discovered in 1911, and for 75 years was only known in some metals and metallic alloys at temperatures below 30 K. In 1986 so-called high-temperature superconductivity was discovered in certain ceramic oxides, and has now been observed in temperatures as high as 164 K.