Question

The magnetization (M) – magnetic field (H) curves for four different materials are given below. Which one of these materials is most suitable for use as a permanent magnet?

• A.

  

• B.

  

• C.

  

• D.

  

Hint:

Permanent magnets require \textbf{hard magnetic materials} with large hysteresis loops. Soft magnets, used in transformer cores, have very narrow loops to minimize energy loss.

Answer 1

The Correct Option is C

Step 1: Recall the requirement of a permanent magnet.
A good permanent magnet must: - Have high retentivity (remanence): ability to retain magnetization after external field is removed. - Have high coercivity: ability to withstand demagnetizing forces without losing magnetization. - Exhibit a large hysteresis loop area, which means more energy is required to demagnetize it.
Step 2: Analyze each option.
(A) The loop is moderate, with some remanence, but coercivity is small compared to (C). Not ideal.
(B) The loop is very narrow → low coercivity and remanence. This material is suitable for soft magnetic materials (transformer cores), not permanent magnets.
(C) The loop is very wide, with both high coercivity and high remanence → this is the most suitable for permanent magnets.
(D) Very narrow loop, low retentivity → again soft magnetic material, not a permanent magnet.
Step 3: Select the most suitable material.
Among the given options, (C) shows the widest hysteresis loop, highest coercivity, and maximum retentivity → best suited for permanent magnets. Final Answer: \[ \boxed{(C) \ \text{Material with wide hysteresis loop}} \]