The variation of magnetic susceptibility $(\chi )$ with temperature for a diamagnetic substance is best represented by:

$A$ sample of paramagnetic salt contains $2 \times 10^{24}$ atomic dipoles each of dipole moment $1.5 \times 10^{-23} \text{ J T}^{-1}$. The sample is placed under a homogeneous magnetic field of $0.6 \text{ T}$ and cooled to a temperature of $4.2 \text{ K}$. The degree of magnetic saturation achieved is $20 \%$. What is the total dipole moment of the sample for a magnetic field of $0.9 \text{ T}$ and a temperature of $2.8 \text{ K}$ (in $\text{ J T}^{-1}$)?

$A$ paramagnetic salt contains $2 \times 10^{26} \, m^{-3}$ atomic dipoles. Each dipole has a magnetic moment of $1.5 \times 10^{-23} \, A \cdot m^2$. What is the saturation magnetization?

Which of the following curves represents the variation of magnetic moment $(M)$ with temperature $(T)$ for a ferromagnetic material?

$A$ ball of superconducting material is dipped in liquid nitrogen and placed near a bar magnet.
$(i)$ In which direction will it move?
$(ii)$ What will be the direction of its magnetic moment?

Electromagnets are made of soft iron because soft iron has