JEE Main & Advanced Physics Electro Magnetic Induction Question Bank Critical Thinking

  • question_answer
    A 50 volt potential difference is suddenly applied to a coil with \[L=5\times {{10}^{-3}}\] henry and \[R=180\,ohm\]. The rate of increase of current after 0.001 second is [MP PET 1994]

    A)            27.3 amp/sec                       

    B)            27.8 amp/sec

    C)            2.73 amp/sec                       

    D)            None of the above

    Correct Answer: D

    Solution :

                       The rate of increase of current                    \[=\frac{di}{dt}=\frac{d}{dt}{{i}_{0}}\left( 1-{{e}^{-Rt/L}} \right)=\frac{d}{dt}{{i}_{0}}-\frac{d}{dt}{{i}_{0}}{{e}^{-Rt/L}}\]                    \[=0-{{i}_{0}}{{e}^{-Rt/L}}.\frac{d}{dt}\left( -\frac{Rt}{L} \right)={{i}_{0}}\frac{R}{L}{{e}^{-Rt/L}}\]            \[=\frac{50}{180}\times \frac{180}{5\times {{10}^{-3}}}\times {{e}^{-(180\times 0.001)/(5\times {{10}^{-3}})}}\]\[={{10}^{4}}\times {{e}^{-36}}A/\sec \]


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