Question

Electromagnets are made of soft iron because soft iron has

• A. low retentivity and high coercive force
• B. high retentivity and high coercive force
• C. low retentivity and low coercive force
• D. high retentivity and low coercive force

Answer 1

The Correct Option is C

Electromagnets are typically made of soft iron due to their specific magnetic properties. Let's understand the reason behind this choice:

1. Concept of Retentivity: Retentivity is the ability of a material to retain a certain amount of residual magnetic field when the external magnetizing field is removed. Soft iron has low retentivity, meaning it does not retain magnetism when the magnetizing force is removed. This characteristic is essential for electromagnets, as they need to be demagnetized quickly.
2. Concept of Coercive Force: Coercive force is the amount of reverse magnetic field which must be applied to a magnetic material to make its magnetic flux return to zero. Soft iron has low coercive force, which implies that it can easily get magnetized and demagnetized. This is vital for electromagnets, which are often switched on and off.
3. Conclusion: For electromagnets, which require frequent magnetization and demagnetization, low retentivity and low coercive force are advantageous properties. Hence, the correct answer is "low retentivity and low coercive force".

This makes soft iron an ideal material for electromagnets, facilitating their use in various applications where magnetic fields are dynamically controlled.