As every Friday, the weekly column "A Taste of Physics" is back — number 11.
This time: the remarkable properties of superconductors and the Meissner effect.
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**What is a superconductor?**
When electric current flows through a material, the material's atoms resist the passage of that current, converting some of the energy into heat.
A superconductor is a material that, when cooled below a certain threshold temperature, loses its electrical resistance entirely — and current flows through it with absolutely no resistance.
The temperature required to achieve superconductivity is extremely low, far below zero, and can therefore only be reached under laboratory conditions.
Considerable efforts are underway — so far without success — to create superconductors that operate at room temperature.
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The Meissner effect was described in 1933 by a scientist named Walther Meissner.
Meissner discovered that superconductors expel magnetic fields from their interior completely.
When a magnet is placed in the air above a superconductor, the magnetic field it generates "attempts" to induce a magnetic effect within the superconductor.
The Meissner effect causes the superconductor to repel that magnetic field — and in doing so, causes the magnet to levitate above it.
In the video: a demonstration of the Meissner effect — a magnet levitating above a superconductor cooled to its critical temperature.
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