$A$ 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,$T_C$.

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

$A$ 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 $\text{ A-m}^2$)

Fill in the blank :
$(i)$ The domain size is ...... .
$(ii)$ The domain contains about ...... atoms.

Consider the following statements regarding paramagnetic substances:
$A$. They are weakly attracted by an external magnetic field.
$B$. They are strongly attracted by an external magnetic field.
$C$. Their magnetic susceptibility $(\chi)$ is small and positive.
$D$. In a non-uniform magnetic field, they move from a region of strong magnetic field to a region of weak magnetic field.
Which of the above statements are correct?

In a permanent magnet at room temperature,