Question

In the circuit shown in figure, switch S is shifted to position 2 from position 1 at $t=0$, having been in position 1 for a long time. The current in the circuit just after shifting of switch will be : (battery and both the inductors are ideal)

• A. $\frac{4}{5}\frac{E}{R}$
• B. $\frac{5}{4}\frac{E}{R}$
• C. $\frac{5}{9}\frac{E}{R}$
• D. $\frac{E}{R}$

Answer 1

Answer: (C)

$\frac{5}{9}\frac{E}{R}$

Let $i_1$ be the current in the circuit before shifting
$i_1=\frac{E}{R}$
Since the flux associated with the inductors will be same just before and just after shifting, therefore
$i_{1}5L=i_{2}9L{i}_2=\frac{5}{9}\frac{E}{R}$