Question

Soft iron is used to make the core of transformer because of its ...........

• A. low coercivity and low retentivity
• B. low coercivity and high retentivity
• C. high coercivity and high retentivity
• D. high coercivity and low retentivity

Hint:

For transformer cores, materials with low coercivity and low retentivity are preferred as they can easily change their magnetization without retaining it.

Answer 1

The Correct Option is A

Step 1: Core materials in transformers.
Soft iron is used in transformer cores because it has low coercivity and low retentivity, meaning it can easily magnetize and demagnetize without retaining a significant magnetic field after the current is switched off.
Step 2: Analyzing the options.

- (1) low coercivity and low retentivity: Correct. Soft iron is ideal for transformers because it easily magnetizes and demagnetizes.
- (2) low coercivity and high retentivity: Incorrect. High retentivity would cause the core to retain magnetic properties, which is undesirable in transformer operation.
- (3) high coercivity and high retentivity: Incorrect. High coercivity is characteristic of hard magnetic materials, which do not easily demagnetize.
- (4) high coercivity and low retentivity: Incorrect. This combination is not ideal for transformer cores.

Step 3: Conclusion.
Soft iron is used for its low coercivity and low retentivity, corresponding to option (1).