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:

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 is represented by the area enclosed by a hysteresis loop?

If the given figure shows the relation between magnetic field ($B$ - along $y$-axis) and magnetic intensity ($H$ - along $x$-axis) of a ferromagnetic material,then the point that represents the coercivity of the material is

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.

The figure illustrates how $B$,the flux density inside a sample of unmagnetised ferromagnetic material,varies with $B_0$,the magnetic flux density in which the sample is kept. For the sample to be suitable for making a permanent magnet: