$A$ long solenoid has $1000$ turns per metre and carries a current of $1 \, A$. It has a soft iron core of $\mu_r = 1000$. The core is heated beyond the Curie temperature,$T_C$.

In a ferromagnetic material,below the Curie temperature,a domain is defined as:

$A$ sample of paramagnetic salt contains $20 \times 10^{24}$ atomic dipoles each of dipole moment $1.5 \times 10^{-23} \ J \ T^{-1}$. The sample is placed under a homogeneous magnetic field of $0.84 \ T$,and cooled to a temperature of $4.2 \ K$. The degree of magnetic saturation achieved is equal to $15 \%$. What is the total dipole moment (approximate) of the sample for a magnetic field of $0.98 \ T$ and a temperature of $2.8 \ K$? (Assume Curie's law).

The variation of the intensity of magnetisation $(I)$ with respect to the magnetising field $(H)$ in a diamagnetic substance is well described by the graph

If $\chi$ stands for the magnetic susceptibility of a substance, $\mu$ for its magnetic permeability, and $\mu_0$ for the permeability of free space, then which of the following is correct?

Steel is preferred over soft iron for permanent magnets because