JEE Main & Advanced Physics Alternating Current / प्रत्यावर्ती धारा Question Bank Self Evaluation Test - Alternating Current

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

    A) \[\frac{V{{R}_{1}}{{R}_{2}}}{\sqrt{R_{1}^{2}+R_{2}^{2}}}\] at t=0  and \[\frac{V}{{{R}_{2}}}\] at \[t=\infty \]

    B) \[\frac{V}{{{R}_{2}}}\] at t=0 and \[\frac{V({{R}_{1}}+{{R}_{2}})}{{{R}_{1}}{{R}_{2}}}\] at \[t=\infty \]

    C) \[\frac{V}{{{R}_{2}}}\] at t=0 and \[\frac{V{{R}_{1}}{{R}_{2}}}{\sqrt{R_{1}^{2}+R_{2}^{2}}}\] at \[t=\infty \]

    D) \[\frac{V({{R}_{1}}+{{R}_{2}})}{{{R}_{1}}{{R}_{2}}}\] at t=0 and \[\frac{V}{{{R}_{2}}}\] at \[t=\infty \]

    Correct Answer: C

    Solution :

    [c] At t = 0, no current will flow through L and \[{{R}_{1}}\] \[\therefore \] Current through battery \[=\,\frac{V}{{{R}_{2}}}\] At \[t=\infty \] effective resistance, \[{{R}_{eff}}=\frac{{{R}_{1}}{{R}_{2}}}{{{R}_{1}}+{{R}_{2}}}\] \[\therefore \] Current through battery\[=\frac{V}{{{R}_{eff}}}=\frac{V\,({{R}_{1}}{{R}_{2}})}{({{R}_{1}}+{{R}_{2}})}\]


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