Q.A magnetic material, when placed in a magnetising field of intensity $H = 1000\ \text{A/m}$, acquires an intensity of magnetisation $M = 0.5\ \text{A/m}$. Calculate its magnetic susceptibility, its relative permeability, and its absolute permeability, and state whether the material is diamagnetic or paramagnetic.

Given $H=1000\ \text{A/m}$, $M=0.5\ \text{A/m}$.

Susceptibility: $\chi = M/H = 0.5/1000 = 5\times10^{-4}$.

Relative permeability: $\mu_r = 1+\chi = 1+5\times10^{-4} = 1.0005$.

Absolute permeability: $\mu = \mu_0\mu_r = (4\pi\times10^{-7})\times1.0005$

$\mu \approx 1.2566\times10^{-6}\times1.0005 \approx 1.257\times10^{-6}\ \text{T}\cdot\text{m/A}$ …

Find $\chi=M/H$ first, then $\mu_r=1+\chi$, then $\mu=\mu_0\mu_r$; read the mat …

• Forgetting to multiply by $\mu_0$ when finding the absolute permeability $\mu$ (leaving the answer as just $\mu_r$). …