Proper explanation for the Meissner effect (1 Viewer)

[porcupinetree]

Ok, I've been reading a lot about the Meissner effect and have looked at old threads on this forum which ask similar questions to mine, but haven't been able to find a good answer. In the situation where a magnet is placed on a warm superconductor, which is then cooled, and the magnet will start to hover, I understand that this is meant to occur due to 'repulsion of magnetic fields' (instead of eddy currents, which may be responsible for some levitation when the magnet is placed [creating a change of flux] onto an already cooled superconductor). But I have not been able to find a decent explanation as to HOW the field is expelled. What is actually happening to make the flux expelled if there is no change in flux to induce eddy currents?

Also, I did also read something which suggested that in an exam answer we must mention something about currents/induced currents?? What is this about, if it's true? Is it part of the proper explanation as to how the field is repelled?

Thanks.

 

[InteGrand]

A proper explanation would require something like the London Equations: http://en.wikipedia.org/wiki/London_equations

 

[Kaido]

At HSC level: Changing Magnetic fields induce currents in the super (F-law). The currents flow in such a direction such that the magnetic field it creates opposes that which created it (L-law). This causes the Meissner effect such that no flux lines can penetrate it. The upward magnetic force from repulsion between the magnet and the superconductor is equal to the weight force of the magnet, thus causing it to hover above the superconducting disk

However, this explanation is far from the real phenomenon of flux pinning by vortex states and 'quantum locking' as a result of a need to conserve energy and superconductivity

 

[Fizzy_Cyst]

An understanding of this is far beyond the HSC course. It's irrelevant!

On a side note:

http://www.sciencealert.com/scientists-have-discovered-a-new-state-of-matter-the-jahn-teller-effect

 

[Kaido]

Hey Fizzy, how do i approach the magnetic levitation experiment and background information on this? We can only use type II's for experiments, but the explanation for the 'levitation' that occurs in type II's is vastly different from type I's (which is the expected explanation)