The SI unit of magnetic permeability is

The correct answer is Option (2) → \( \mathrm{Wb\,m^{-1}\,A^{-1}} \)

The magnetic permeability \( \mu \) of a material is defined through \( B=\mu H \). So its unit is the unit of the magnetic field \( B \) (tesla) divided by the unit of the magnetic intensity \( H \) (\( \mathrm{A\,m^{-1}} \)).

    \( \begin{aligned} \mu &= \frac{B}{H} \\ &= \frac{\mathrm{T}}{\mathrm{A\,m^{-1}}} \\ &= \mathrm{T\,m\,A^{-1}} \end{aligned} \)

Since \( 1\,\mathrm{Wb}=1\,\mathrm{T\,m^{2}} \), a tesla is \( \mathrm{Wb\,m^{-2}} \):

    \( \begin{aligned} \mathrm{T\,m\,A^{-1}} &= \mathrm{Wb\,m^{-2}\times m\,A^{-1}} \\ &= \mathrm{Wb\,m^{-1}\,A^{-1}} \end{aligned} \)

It is the relative permeability \( \mu_r=\mu/\mu_0 \) that has no unit.

NCERT (2026-27):
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