The intensity of magnetisation $I$ is plotted against the magnetising field $H$ for different substances. The curves $A$ and $B$ shown in the adjoining figure are associated with

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

Which of the following statements is incorrect about hysteresis?

The coercivity of a small magnet where the ferromagnet gets demagnetized is $3 \times 10^3 \ Am^{-1}$. The current required to be passed in a solenoid of length $10 \ cm$ and number of turns $100$,so that the magnet gets demagnetized when inside the solenoid,is:

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,

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