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

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

What is Curie temperature? And what is retentivity?

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

The $B-H$ curve for a ferromagnet is shown in the figure. The ferromagnet is placed inside a long solenoid with $1000 \text{ turns/cm}$. The current that should be passed in the solenoid to demagnetize the ferromagnet completely is

$A$ 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 $\text{ A}$)