Question 39: Electromagnetic Induction

Question

Figure shows the circuit that contains three resistances ( $9 \Omega$ each) and two inductors ( 4 mH each). The reading of ammeter at the moment switch $K$ is turned ON , is $\_\_\_\_$ A.

Accepted Answer

The ammeter is placed in the main line to measure the total current drawn from the battery.
An inductor resists any sudden change in the current flowing through it due to self-induction (Lenz's Law). The induced EMF opposes the applied voltage.
Before the switch K is turned ON , the current in the circuit is zero. At the exact moment the switch is turned ON $(t=0)$, the inductors will strongly oppose the sudden increase in current.
Therefore, at $\mathrm{t}=0$, the current through any branch containing an inductor is exactly zero. Effectively, the inductors act as open circuits.
Because the inductors act as open circuits the moment the switch is closed, no current flows through those two branches.
So, the initial current (I) drawn from the battery using Ohm's Law is:
$$ I=\frac{V}{R} \Rightarrow I=\frac{9}{9} A=1 A $$
Therefore, the total reading of the ammeter at the exact moment the switch is turned ON is 1 A . Hence, option (C) is correct.

Answer

2

Answer

3

Answer

1

Answer

zero

Electromagnetic Induction

Figure shows the circuit that contains three resistances ( 9 \Omega each) and two inductors ( 4 mH each). The reading of ammeter at the moment switch K is turned ON , is \_\_\_\_ A.

Choose the correct answer: