Superconductivity
In normal state all conductors exhibit resistance to the passage of electric current
The electrical resistance of some materials however goes to zero at very low temperatures --> they become superconductors
discovered in 1911 by Kamerlingh Onnes
normal superconductivity in simple metals --> 3-10 0K (-270 0C) (liquid Helium temperature --> not suitable for practical applications)
superconductivity in some alloys and compounds up to 32-39 0K
superconductivity at low temperatures explained by the BCS model
Hit in superconductivity 1986 in : High Tc superconductors (ceramics) become superconductors at temperatures as high as 125 0K (liquid nitrogen temperature --> suitable for practical applications) --> no accepted theory for them
problems today: low critical current, making wires, raising more Tc
important property of superconductors: expel magnetic field (possible magnetic levitation)