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Magnetisation for vacuum is _______.

Asked in GSEB Board July 2016 · Magnetisation, intensity and susceptibility

Answer: (4) zero

Step-by-step solution

Idea: magnetisation is the net magnetic dipole moment per unit volume of a material, M=(mₙₑₜ)/V.

Vacuum contains no atoms, so there are no permanent dipoles to align and none to induce: mₙₑₜ=0.

Hence M=0, and with χ=M/H the susceptibility of vacuum is zero as well.

This is consistent with B=μ₀(H+M) reducing to B=μ₀H in vacuum, which is how μ₀ is defined.

So the magnetisation of vacuum is zero.

Why the other options are wrong

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