6.2 Meissner Effect

Question 1

Describe the Meissner Effect

Answer 1

If a material in a superconducting state is subject to a changing magnetic field, then: (B < B_C)

• A current is induced opposing the effect of the external magnetic field
• This current is strong enough that the internal magnetic field is 0

Question 2

What type of current is induced in the Meissner effect and what are the consequences of this?

Answer 2

Persistent current

• Remains even if the external magnetic field is constant
• The current is restricted to the surface layer and shields the inside of the material, “expelling” the field

Question 3

What does the Meissner effect predict about the behaviour of a material?

Answer 3

That it behaves as a perfect diamagnet, with the magnetic susceptability = -1 below T_c