Wiki143:Today's second feature/January 15, 2006
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Superconductivity is a phenomenon occurring in certain materials at low temperatures, characterised by the complete absence of electrical resistance and the exclusion of the interior magnetic field (the Meissner effect). The Meissner effect can be used to demonstrate superconducting magnetic levitation. Here a block of "high temperature" ceramic superconductor, cooled in a bath of liquid nitrogen, repels the round permanent magnet above. Flux pinning stops the magnet from sliding away.
Photo credit: Pacific Northwest National Laboratory