$A$ paramagnetic material has $10^{28} \text{ atoms/m}^3$. Its magnetic susceptibility at temperature $350 \text{ K}$ is $2.8 \times 10^{-4}$. Its susceptibility at $300 \text{ K}$ is

$A$ sample of a paramagnetic salt containing $3 \times 10^{24}$ atomic dipoles each of dipole moment $2 \times 10^{-23} \text{ A-m}^2$ is subjected to a uniform magnetic field of $880 \text{ mT}$ and cooled to a temperature of $3.5 \text{ K}$. The degree of magnetic saturation achieved is $10 \%$. If the sample is subjected to a magnetic field of $990 \text{ mT}$ and cooled to a temperature of $2.1 \text{ K}$, then the total dipole moment of the sample is (in $\text{ A-m}^2$)

For two types of magnetic materials $A$ and $B$,the variation of $\frac{1}{\chi}$ ($\chi$: magnetic susceptibility) versus temperature $T$ is shown in the figure. Then:

What is the nature of the magnetic susceptibility of a diamagnetic substance?

Curie's law can be written as

What type of materials can be used to make an electromagnet?