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  • Please,please help me - Electromagnetic Induction and Alternating currents - JEE Main

In the circuit shown below, the key K is closed at t=0 . The current through the battery is

  • Option 1)

    \frac{V(R_{1}+R_{2})}{R_{1}R_{2}}at\; t=0\; and\; \frac{V}{R_{2}}at\; t=\infty

  • Option 2)

    \frac{VR_{1}R_{2}}{\sqrt{R_{1}^{2}+R_{2}^{2}}}\, at\; t=0\; and\; \frac{V}{R_{2}}\, at\; t=\infty

  • Option 3)

    \frac{V}{R_{2}}\, \, at\,t=0\; and\; \, \frac{V(R_{1}+R_{2})}{R_{1}R_{2}}at\; t=\infty

  • Option 4)

    \frac{V}{R_{2}}at\; t=0\; and\;\frac{VR_{1}R_{2}}{\sqrt{R_{1}^{2}+R_{2}^{2}}}\, at\; t=\infty

 

Answers (1)

best_answer

As we learnt in 

Self Inductance -

An emf is induced in the coil or the circuit which oppose the change that causes it. Which is also known back  emf.

- wherein

 

 at t=0, there is no current through inductor

\therefore I=0

as t \rightarrow \infty

I=\frac{V}{R_{eq}}

=\frac{V/R_{1}R_2}{R_1+R_2}

=\frac{V(R_1+R_2)}{R_1+R_2}


Option 1)

\frac{V(R_{1}+R_{2})}{R_{1}R_{2}}at\; t=0\; and\; \frac{V}{R_{2}}at\; t=\infty

Incorrect option

Option 2)

\frac{VR_{1}R_{2}}{\sqrt{R_{1}^{2}+R_{2}^{2}}}\, at\; t=0\; and\; \frac{V}{R_{2}}\, at\; t=\infty

Incorrect option

Option 3)

\frac{V}{R_{2}}\, \, at\,t=0\; and\; \, \frac{V(R_{1}+R_{2})}{R_{1}R_{2}}at\; t=\infty

Correct option

Option 4)

\frac{V}{R_{2}}at\; t=0\; and\;\frac{VR_{1}R_{2}}{\sqrt{R_{1}^{2}+R_{2}^{2}}}\, at\; t=\infty

Incorrect option

Posted by

divya.saini

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