In the circuit shown in the figure, $E=15 \mathrm{V}, R_1=1 \mathrm{\Omega },\mathrm{ }{\mathrm{R}}_2=1 \mathrm{\Omega },\mathrm{ }{\mathrm{R}}_3=2 \mathrm{\Omega }$ and $L=1.5 \mathrm{H}$. The currents flowing through $R_1, R_2$ and $R_3$ are $i_1, i_2$ and $i_3$ , respectively.


Immediately after connecting switch $S_w$,

• A

  $i_3=0 \mathrm{A}$ and $\frac{d{i}_3}{dt}=0 \mathrm{A} {\mathrm{s}}^{-1}$
• Correct answer
  B

  $i_3=0 \mathrm{A}$ and $\frac{d{i}_3}{dt}\ne 0 \mathrm{A} {\mathrm{s}}^{-1}$
• C

  $i_3=0 \mathrm{A}$ , and rate at which magnetic energy stored is not zero
• D

  None of these

Solution

At $t = 0$ , circuit can be considered as follows.



After a long time, circuit can be considered as follows.



The current $i_3$ is zero at the instant of closing the switch but with time it grows and achieves a non-zero value, hence $\frac{d{i}_3}{dt}\ne 0$

Hence, the correct answer is option: 'B'.