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JEE Main & Advanced Physics Electro Magnetic Induction JEE PYQ-Electro Magnetic Induction

  • question_answer
    An inductor (L = 0.03 H) and a resistor \[(R=0.15k\Omega )\]are connected in series to a battery of 15V EMF in a circuit shown below. The key \[{{K}_{1}}\] has been kept closed for a long time. Then at \[t=0,{{K}_{1}}\]is opened and key \[{{K}_{2}}\] is closed simultaneously. At t = 1ms, the current in the circuit will be : \[\left( {{e}^{5}}\cong 150 \right)\]                                  [JEE MAIN 2015]

    A) 6.7 mA

    B) 0.67 mA

    C) 100 mA

    D) 67 mA

    Correct Answer: B

    Solution :

    Sol. [b]
    \[i=\frac{15}{0.15\times {{10}^{+3}}}\]
    \[15\times {{10}^{-2}}\times {{10}^{+3}}\]
    \[1={{10}^{-1}}{{e}^{-1\frac{Rt}{L}}}\]
    \[=\frac{1}{150}\]            \[\frac{0.15\times {{10}^{3}}}{0.03}\times {{10}^{-3}}\]
    \[\frac{1}{1500}\]
    \[=1\]    \[{{10}^{-2}}\]
    \[=6.67\times {{10}^{-4}}\]
    \[=0.667\times {{10}^{-3}}\]
    \[=0.667mA\]


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