Q. 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
A) $OQ$ should be large, $OR$ should be small
B) $OQ$ and $OR$ should both be large
C) $OQ$ should be small and $OR$ should be large
D) $OQ$ and $OR$ should both be small
Explanation
(b) In the given figure $OQ$ refers to retentivity while $OR$ refers to coercivity. For permanents both retentivity and coercivity should be high
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.