Two types of steel are characterized by the hysteresis loops shown in figure (a) and (b). The loops are obtained in the processes of magnetization and demagnetization of the steels. Which of the two types is best suited for using as the core of a transformer and which, for using as a permanent magnet ?

Question

G1 Physics · Accepted Answer

Transformer cores need low hysteresis loss, hence a narrow loop; permanent magnets need high retentivity/coercivity, hence a broad loop. From the figure A is narrow and B is broad. Therefore D.