Question

A region where no magnetic field is desired is surrounded by a sheet of low-resistivity metal.?

A) Will this sheet shield the interior from a rapidly changing magnetic field outside?

B) Will it act as a shield to a static magnetic field?

C) What if the sheet is superconducting (resistivity = 0)?

Answer 1: The superconducting sheet will shield the interior from magnetic fields.

Answer 2: The superconducting sheet will not shield the interior from magnetic fields.

Answer 1

what basically happens is that if the temperature is lowered down, the resistivity of the material is decresed too. if resistivity is decresed then conductivity is incresed which means an electrical current is likely to loop around for much longer time creating the magnetic field which can prevent most of the magnetic flux from entering inside the material. So, yes it does shield the interior from external magnetic field.

If the sheet is a superconductor then the resistivity is zero meaning it is completely conductive. hence the current loops around for indefinte time and stops the external magnetic field from getting inside as long as it doesn't cross the critical magnectic field . Of course there is a crictical temperature also above which superconductor go through phase transistion and become normal conductor.