A soft iron bar is inserted inside a current-carrying solenoid. The magnetic field inside the solenoid:(a) will decrease               (b) will increase(c) will become zero        (d) will remain the same

Explanation

If a soft iron bar is inserted inside a current-carrying solenoid, then the magnetic field inside the solenoid will increase because it magnetizes the iron bar as it can easily gain magnetic properties when current is passed around it and loses the magnetic properties as the current is switched off.

And, as a result, the strength of the magnetic field inside the solenoid gets increased.