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

The relation $H \propto I$ and the susceptibility $\chi = \frac{I}{H}$ are not applicable for which of the following substances?

The magnetic susceptibility of a paramagnetic material at $-73^{\circ} C$ is $0.0075$. Its value at $-173^{\circ} C$ will be

Core of electromagnets are made of ferromagnetic material which has

Which of the following is most suitable for the core of electromagnets?

$A$ 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 $\text{ J T}^{-1}$)?