The magnetic field produced by a solenoid increases by:

Correct option is B

• A solenoid is a long coil of wire through which an electric current passes. When a solenoid is energized, it generates a magnetic field similar to that of a bar magnet.
• Placing a soft iron core inside the solenoid increases the magnetic field produced. This is because soft iron is a ferromagnetic material that becomes magnetized when exposed to a magnetic field, thereby enhancing the magnetic field of the solenoid. The soft iron core does not retain magnetization once the current is turned off, but it increases the field strength when the current is on.

•  Changing the direction of the solenoid doesn't necessarily increase the magnetic field; it only reverses its polarity.
• Decreasing the number of turns would decrease the magnetic field, not increase it.
• Changing the direction of the current will reverse the magnetic field's direction but does not increase its strength.