If $\chi$ is the magnetic susceptibility and $\mu_{r}$ is the relative permeability of a ferromagnetic substance, then:

Consider the following two statements $A$ and $B$ and identify the correct choice in the given answers.
$A$. Paramagnetism is explained by domain theory.
$B$. Susceptibility of a diamagnetic substance is independent of temperature.

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

If a diamagnetic solution is poured into a $U-$ tube and one arm of this $U-$ tube is placed between the poles of a strong magnet with the meniscus in line with the field,then the level of the solution will:

The magnetic susceptibility $\chi$ for superconductors is . . . . . . .

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