Question

Permanent magnet has properties retentivity and coercivity respectively as:
A. high-high
B. low-low
C. low-high
D. high-low

Answer 1

A good permanent magnet should produce a high magnetic field with a low mass and should be stable against the influences which would demagnetize it. The desirable properties of such magnets are typically stated in terms of the retentivity (remanence) and coercivity of the magnet materials.

Complete step by step solution:

Retentivity$\left( R \right)$: It is a measure of the remaining magnetization when the driving field$\left( H \right)$is dropped to zero.
Coercivity$\left( C \right)$: It is a measure of the reverse field needed to drive the magnetization into zero after being saturated.

The materials suitable for permanent magnets must have high retentive, high coercivity and high permeability.

Hence the correct option is (A).

Note: The material used for permanent magnet must be high retentively so that magnet be strong and that of high coercively so that the magnetism does not unify out on applying strong magnetic field through it.