Question

The B-H curve shown in the fig. associated with

A). (i) diamagnetic and (ii) paramagnetic substance
B). (i) paramagnetic and (ii) ferromagnetic substance
C). (i) soft iron and (ii) steel respectively
D). (i) steel and (ii) soft iron respectively

Answer 1

Hint: The diagram shown in the figure represents the behaviour of a material taken through a cycle of magnetization. We need to study the property of retentivity and coercivity from the hysteresis loop that are given on the Y and X axis respectively.

Complete step by step answer:
The figure shows the hysteresis loop that represents the Magnetic field induction (B) on the Y-axis and magnetizing force (H) on the X-axis.
The value of magnetic field induction left in the specimen when the magnetising force is reduced to zero is called Retentivity of the material and it is seen on the Y-axis. To reduce the retentivity to zero we need to apply a magnetizing force in the opposite direction. This value of magnetising force is called the coercivity of the material and it is on the X- axis.
The retentivity of soft iron is greater than the retentivity of steel as it gets more strongly magnetised than steel. Also, soft iron loses its magnetism more rapidly than steel so its coercivity is less than that of steel. Accordingly, it can be seen from the figure that (i) represents soft iron and (ii) is steel.
Hence, the correct answer is option C. (i) soft iron and (ii) steel respectively.

Note: The students must remember that the area of B-H curve represents hysteresis loss. Note that hysteresis loss in case of soft iron is much less than the hysteresis loss due to steel. Steel and Iron are both ferromagnetic materials so options A , B are not correct.