For substances,hysteresis $(B-H)$ curves are given as shown in the figures. Which of the following is best for making a temporary magnet?

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 $J$)

The only property possessed by ferromagnetic substances is

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

The coercivity of a magnet,where the ferromagnet gets completely demagnetized,is $3 \times 10^{3} \text{ A m}^{-1}$. The minimum current required to be passed in a solenoid having $1000 \text{ turns m}^{-1}$,so that the magnet gets completely demagnetized when placed inside the solenoid,is:

The magnet can be completely demagnetized by