Explanation: An electromagnet is constructed using soft iron because it has high magnetic permeability and low retentivity, meaning it can easily gain and lose magnetism when the electric current is switched on or off.
Why Soft Iron?
1. High Permeability – Soft iron allows magnetic field lines to pass through it efficiently.
2. Low Retentivity – It does not retain magnetism after the current is turned off, making it ideal for temporary magnets like electromagnets.
3. Reduces Energy Loss – Soft iron minimizes energy loss due to hysteresis, improving efficiency.
Other Options Explained:
(A) Aluminium – Non-magnetic and unsuitable for electromagnets.
(B) Steel – Retains magnetism (high retentivity), making it better for permanent magnets but not for electromagnets.
(C) Nickel – Magnetic but not commonly used for electromagnets.
Thus, the correct answer is (D) Soft Iron.
Explanation by: Mr. Dubey
Why Soft Iron?
1. High Permeability – Soft iron allows magnetic field lines to pass through it efficiently.
2. Low Retentivity – It does not retain magnetism after the current is turned off, making it ideal for temporary magnets like electromagnets.
3. Reduces Energy Loss – Soft iron minimizes energy loss due to hysteresis, improving efficiency.
Other Options Explained:
(A) Aluminium – Non-magnetic and unsuitable for electromagnets.
(B) Steel – Retains magnetism (high retentivity), making it better for permanent magnets but not for electromagnets.
(C) Nickel – Magnetic but not commonly used for electromagnets.
Thus, the correct answer is (D) Soft Iron.