The area of the hysteresis loop of a material is equivalent to $250 \, J$. When $10 \, kg$ of the material is magnetized by an alternating field of $50 \, Hz$, what is the energy lost in one hour? (Given: density of the material is $7.5 \, g/cm^3$)

Answer the following questions:
$(a)$ Explain qualitatively on the basis of the domain picture the irreversibility in the magnetisation curve of a ferromagnet.
$(b)$ The hysteresis loop of a soft iron piece has a much smaller area than that of a carbon steel piece. If the material is to go through repeated cycles of magnetisation,which piece will dissipate greater heat energy?
$(c)$ '$A$ system displaying a hysteresis loop such as a ferromagnet,is a device for storing memory?' Explain the meaning of this statement.
$(d)$ What kind of ferromagnetic material is used for coating magnetic tapes in a cassette player,or for building 'memory stores' in a modern computer?
$(e)$ $A$ certain region of space is to be shielded from magnetic fields. Suggest a method.

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?

The study of the hysteresis curve for a given material is used to estimate the:

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

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