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

The energy dissipated per unit volume per cycle in the hysteresis of an iron sample of mass $10 \, kg$ is $200 \, J \, m^{-3} \, cycle^{-1}$. The density of iron is $7500 \, kg \, m^{-3}$. The loss of energy per hour at $50 \, cycle \, s^{-1}$ is: (in $J$)

$A$ bar magnet has a coercivity of $4 \times 10^3 \, A \, m^{-1}$. It is desired to demagnetize it by inserting it inside a solenoid $12 \, cm$ long and having $60$ turns. The current that should be sent through the solenoid is . . . . . . $A$.

Magnetic materials used for making permanent magnets $(P)$ and magnets in a transformer $(T)$ have different properties. Of the following,which property best matches the type of magnet required?

Which of the following statements is incorrect about hysteresis?

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?