$A$ paramagnetic sample shows a net magnetization of $0.8 \text{ A m}^{-1}$ when placed in an external magnetic field of strength $0.8 \text{ T}$ at a temperature of $5 \text{ K}$. If the temperature is raised to $20 \text{ K}$, then the magnetization becomes: (in $\text{ A m}^{-1}$)

What is a ferromagnetic substance? What is a magnetic domain?

$A$ sample of paramagnetic salt contains $20 \times 10^{24}$ atomic dipoles each of dipole moment $1.5 \times 10^{-23} \ J \ T^{-1}$. The sample is placed under a homogeneous magnetic field of $0.84 \ T$,and cooled to a temperature of $4.2 \ K$. The degree of magnetic saturation achieved is equal to $15 \%$. What is the total dipole moment (approximate) of the sample for a magnetic field of $0.98 \ T$ and a temperature of $2.8 \ K$? (Assume Curie's law).

If the magnetic dipole moment of an atom of diamagnetic material,paramagnetic material,and ferromagnetic material are denoted by $\mu_d, \mu_p, \mu_f$ respectively,then:

The Curie-Weiss law is obeyed by iron at a temperature ......

The magnetic needle of a magnetic compass is made up of $\qquad$ .