A solenoid is connected to a battery so that a steady current flows through it. If an iron core is inserted into the solenoid, then the current in the coil (a) will not change (b) will increase (c) will decrease (d) may increase or decrease depending upon the direction of the current

Answer: (c). Inserting the iron core raises μr, so L and the flux through the coil increase. By Lenz's law a back emf -LdI/dt (from the rising flux) opposes the battery while the core is moving in. So the current falls while the core is being inserted (it returns to V/R once the core stops). So the answer is (c) will decrease.

A solenoid is connected to a battery so that a steady current flows… | MHT CET 2026 (19 Apr, Shift 2)

Q14MHT CET 2026 · 19 APR · SHIFT 2Medium

Self-Inductance & Energy

A solenoid is connected to a battery so that a steady current flows through it. If an iron core is inserted into the solenoid, then the current in the coil

Show answer and solution

Answer: (c)

Inserting the iron core raises $\mu_r$ , so $L$ and the flux through the coil increase.
By Lenz's law a back emf $-L\dfrac{dI}{dt}$ (from the rising flux) opposes the battery while the core is moving in.
So the current falls while the core is being inserted (it returns to $V/R$ once the core stops).
So the answer is (c) will decrease.

Report a mistake

Self-Inductance & Energy question from MHT CET 2026 (19 Apr, Shift 2)

More questions on Self-Inductance & Energy