Identify the paramagnetic substance.

Which of the following statements is correct for diamagnetic materials?

$A$ 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).

The materials having negative magnetic susceptibility are

The variation of magnetic susceptibility $(\chi)$ with magnetising field $(H)$ for a paramagnetic substance is represented by which of the following graphs?

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