Q. In the inductive circuit given in the figure, the current rises after the switch is closed. At instant when the current is $15\ mA$, then potential difference across the inductor will be

A) Zero
B) $240V$
C) $180V$
D) $60V$
Explanation

(c) Here: Current in the circuit
$(i) = 15\ mA = 15 \times 10^{- 3}A$
Resistance $R = 4000\ Volt$
Applied voltage in the circuit $= 240\ V$
At any instant, the $emf$ of the battery is equal to the sum of potential drop on the resistor and the $emf$ developed in the induction coil
Hence, $E = iR + L\frac{di}{dt}$
$240 = 15 \times 10^{- 3} \times 4000 + L\frac{di}{dt}$
Hence, $L\frac{di}{dt} = 240 - 60 = 180\ V$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.