Question

A metal at very low temperature has magnetic permeability \(\mu = 0\). It is a perfect

• A. Paramagnet
• B. Diamagnet
• C. Soft ferromagnet
• D. Hard ferromagnet

Hint:

A superconductor is a perfect diamagnet due to the Meissner effect: \[ B=0 \text{ inside the superconductor} \] Hence, it completely expels magnetic field lines.

Answer 1

The Correct Option is B

Concept: At very low temperatures, a superconductor exhibits the Meissner effect, due to which it completely expels magnetic flux from its interior. For a perfect diamagnet, \[ B=0 \] inside the material. Hence, its magnetic permeability becomes \[ \mu=0 \] and magnetic susceptibility is \[ \chi=-1 \]

Step 1:Recall the magnetic properties of different materials. For paramagnetic materials, \[ \mu>\mu_0 \] For ferromagnetic materials, \[ \mu \gg \mu_0 \] For a perfect diamagnetic material (superconductor), \[ \mu=0 \]

Step 2: Identify the material. Given, \[ \mu=0 \] This is the characteristic property of a perfect diamagnet.

Step 3: State the answer. \[ { \text{The metal behaves as a perfect diamagnet.} } \] Hence, the correct option is \[ {(B)} \]