Question

What is the property of retentivity in magnetic materials?

(a) After removal of external magnetic fields, magnetization exists

(b) After removal of external magnetic fields, magnetization doesn’t exist

(c) After removal of internal magnetic fields, magnetization exists

(d) After removal of internal magnetic fields, magnetization doesn’t exist

This question was addressed to me in an interview for job.

My question is taken from Magnetic Materials topic in portion Electrical Engineering Materials of Design of Electrical Machines

Answer 1

Right answer is (a) After removal of external magnetic fields, magnetization exists

To explain: Magnetic materials have the property of retentivity in which the magnetic flux produced acts according to the external magnetic field. When the external field is removed, the magnetization in the materials doesn’t deform immediately.