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For superconductors, μᵣ= ______.

Asked in GSEB Board March 2019 · Dia, para and ferromagnetism

Answer: (1) zero

Step-by-step solution

Idea: a superconductor shows the Meissner effect -- it expels magnetic flux from its interior, so B=0 everywhere inside.

Write B=μ₀μᵣH: with H finite and B=0, the relative permeability must be zero.

The same statement in terms of susceptibility: the induced magnetisation exactly cancels the applied field, so χ=-1 and μᵣ=1+χ=0.

That makes a superconductor a perfect diamagnet, the limiting case of μᵣ<1.

So for superconductors μᵣ is zero.

Why the other options are wrong

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