The area of the hysteresis loop of a substance indicates:

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

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

$A$ bar magnet is demagnetized by inserting it inside a solenoid of length $0.2 \, m$,$100 \, turns$,and carrying a current of $5.2 \, A$. The coercivity of the bar magnet is.....$A/m$

$A$ 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 $^{\circ} C$)

$A$ bar magnet has a coercivity of $4 \times 10^3 \text{ A m}^{-1}$. It is placed inside a solenoid of $12 \text{ cm}$ length and $60$ turns. The current that should be passed through the solenoid to demagnetize the bar magnet is: (in $\text{ A}$)