5. A material has N spins per m3. If Np are the dipoles per m3 parallel to field and Na are the dipoles per m3 anti-parallel to field, the magnetisation is
10. Assertion (A): For a magnetic material M = (?r - 1) H, where M is magnetic dipole moment/m3, H is field intensity A/m and ?r is relative permeability.
Reason (R): ?r can have any value from 0 to hundreds of thousands.
Options
A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A