Answer the following question: (a) Explain qualitatively on the basis of 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 ferromagnet is a device for strong memory? Explain the meaning of this statement.
(d) What kind of ferromagnet 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.

Explanation

Thehystersis curve (B-H curve) of a ferromagnetic material is hown in the following figure.

(a) It can be observed from the given curve that magnetisation persists even when the external field is removed. this reflects the irreversibity of a ferromanget.
(b) The dissipated heat energy is directly proprotional to the area of a hysteresis loop. A carbon steel piece has a greater hysteresis curve area. Hence, it dissiates greater heat energy
(c) The value of magnetisation is mermory of recrod of hystersis loop cycles of magnetisation. These bits of information correspond to the cycle of magnetisation.
Hysteresis loops can be used for storing information.
(d) Ceramic is used for coating magnetic tapes in cassette players and for building memory stores in modern computers.
(e) A certain region of space can be shielded from magnetic fields if it is surrounded by soft iron rings. in such arrangements, the magnetic lines are drawn out of the region.