To protect an instrument from an external magnetic field,it is completely surrounded by:

$A$ uniform magnetic field,parallel to the plane of the paper,exists in space and is initially directed from left to right. When a bar of soft iron is placed in the field parallel to it,the lines of force passing through it will be represented by:

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

Explain ferromagnetism and ferromagnetic substances.

$A$ 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?

An example of a perfect diamagnet is a superconductor. This implies that when a superconductor is placed in an external magnetic field of intensity $B$,the magnetic field $B_s$ inside the superconductor will be such that