An iron ring of relative permeability $μ_r$, is introduced inside a toroidal solenoid having $η$ turns per meter. If the current in the solenoid is I, then the magnetic field in the ring is:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → $μ_oμ_rηI$
Magnetic field inside a toroidal solenoid with an iron core:
$B = \mu H = \mu_0 \mu_r H$
Magnetizing field $H$ of a solenoid: $H = \eta I$
Thus, magnetic field in the iron ring:
$B = \mu_0 \mu_r \eta I$
Final Answer: $B = \mu_0 \mu_r \eta I$