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Levitation
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Levitation

A surprising effect

In a superconductor, there are two different forces that can make a magnet levitate: the Meissner effect and vortex pinning. The Meissner effect expels the magnet from the superconductor while vortex pinning maintains the magnet where it was when the superconductor was cooled. In other words, one rejects while the other pins (yet without attracting). You can observe either one of these forces depending on the nature of the material and the power of the magnet.

In this video, the superconductor with a magnet on top is cooled resulting in a magnetic field. At high temperatures, the magnetic field completely penetrates the material. However, when the material becomes superconducting, the magnet begins to levitate.  From where does this strange effect come?


In a superconductor, the electrons merge into one collective quantum wave called the condensate.

The magnetic field acts to “bend” this wave. But the superconducting wave is rigid and unbendable, otherwise it might break. The superconductor “tries” to protect itself from the magnetic field by expelling it. This is exactly what happens with the Meissner effect.


A magnet (here metallic) creates a magnetic field which goes through any non magnetic material such as the black pellet. When this pellet is cooled and becomes superconducting, it expels the magnetic field. This induces a magnetic force which makes the magnet levitate. This is Meissner Effect.

 

CNRSSociété Française de PhysiqueTriangle de la physique
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CNRSSociété Française de PhysiqueTriangle de la physique