question_answer

The materials suitable for making electromagnets should have

A)  high retentivity and high coercivity                  

B)  low retentivity and low coercivity

C)  high retentivity and low coercivity                   

D)  low retentivity and high coercivity

Correct Answer: C

Solution :

 Electromagnets are made up of soft iron. The soft iron has high retentivity and low coercivity. In electromagnets hysteresis loss should be low and retentivity must be high. Note Retentivity of a substance is a measure of magnetisation remaining in the substance when magnetising field is removed. Coercivity of a substance is the measure of the reverse magnetising field required to destroy the residual magnetism of substance.