Question

A permanent magnet has properties of retentivity and coercivity respectively as

• A. high-high
• B. low-low
• C. low-high
• D. high-low

Answer 1

The correct option is A

high-high

Permanent magnet:

1. A good permanent magnet should create a high magnetic field with a low mass while remaining stable against demagnetizing influences.
2. The ideal qualities of such magnets are often expressed in terms of the magnet materials' retentivity (remanence) and coercivity.

Retentivity(R):

1. It is a measure of the remaining magnetization when the driving field(H) is dropped to zero.
2. A permanent magnet should have high retentivity so that the magnet is strong.

Coercivity(C):

1. It is a measure of the reverse field needed to drive the magnetization into zero after being saturated.
2. Permanent magnets should have high coercivity so that external magnetic fields in opposite directions cannot easily demagnetize the magnet.
3. Hence, the materials suitable for permanent magnets must have high retentivity, high coercivity, and high permeability.

Hence, option A is the correct answer.