Question

Out of the two magnetic materials, 'A' has relative permeability slightly greater than unity while 'B' has less than unity. Identify the nature of the materials 'A' and 'B'. Will their susceptibilities be positive or negative?

Answer 1

For a paramagnetic material, the relative permeability lies between $1<{\mu }_r<1+\epsilon$ and its susceptibility lies between $0<X<\epsilon$.
Hence, 'A' is a para-magnetic material and its susceptibility is positive. This is because its relative permeability is slightly greater than unity. For a diamagnetic material, the relative permeability lies between $0\le {\mu }_r<1$ and its susceptibility lies between $-1<X<0$. Hence, 'B' is a diamagnetic material and its susceptibility is negative. This is because its relative permeability is less than unity. Here ${\mu }_r$ and $x$ refer to the relative permeability and susceptibility.