Which of the following is represented by the area enclosed by a hysteresis loop?

$A$ metal rod is subjected to cycles of magnetisation at the rate of $42 \ Hz$. The density of the metal is $6 \times 10^3 \ kg \ m^{-3}$ and its specific heat capacity is $0.1 \times 10^3 \ cal \ kg^{-1} \ ^{\circ}C^{-1}$. If the area of its $B-H$ loop corresponds to an energy density of $10^{-2} \ J \ m^{-3}$,then the rise in its temperature in one minute is: (in $^{\circ} C$)

If the $B-H$ curves of two samples $P$ and $Q$ of iron are as shown below,then which one of the following statements is correct?

The figure shows the experimentally measured $B$ vs. $H$ variation in a ferromagnetic material. The retentivity,coercivity,and saturation of the material are,respectively:

The figure illustrates how $B$,the flux density,inside a sample of ferromagnetic material varies with external magnetic field $B_0$. For the sample to be suitable for making a permanent magnet,

Magnetic hysteresis is exhibited by . . . . . . magnetic materials.