Magnetic Field Penetration in Superconductors

[Danyon]

Consider a 5 meter by 5 meter and 1cm thick superconducting plate, now place a very strong neodymium magnet against the underside of the plate.The plate is big enough so that the magnetic field does not go around the plate. Does a magnetic field penetrate the plate or is it blocked completely?

The reason I ask is because I thought that perhaps at a large enough distance from the top of the plate the magnetic field from the plate might become weaker and then the magnetic field from the neodymium would become stronger than the field countering it.

The other question I had was what would happen to the magnetic field around a small magnet that was placed tightly inside a hollow one meter long superconductive cylinder? such that the magnets north and south ends point out each end of the cylinder and such that the magnet is flush with the inside of the cylinder.

Would the magnetic field take the short route by simply squeezing between the gap between the superconductor and the magnet, or would the field go all the way out and around the cylinder?

 

[mfb]

The plate is big enough so that the magnetic field does not go around the plate.

No plate of finite size will manage that. The field that does go around is negligible, however. Assuming a type I superconductor (otherwise you don't get the full Meissner effect), you limit the magnetic field to one side of the plate.