BCECE Medical BCECE Medical Solved Papers-2008

  • question_answer
    The inductance of a coil is \[L=10\,H\] and resistance \[R=5\,\Omega \]. If applied voltage of battery is 10 V and it switches off in 1 millisecond, find induced emf of inductor.

    A)  \[2\times {{10}^{4}}V\]

    B)  \[1.2\times {{10}^{4}}V\]

    C)  \[2\times {{10}^{4}}V\]

    D)  None of these

    Correct Answer: A

    Solution :

    Amount of magnetic flux linked with inductor is                 \[\phi =Li\] Now, the emf induced in the inductor is given by                 \[e=-\frac{d\phi }{dt}=-\frac{d}{dt}(Li)\]                 \[=-L\frac{di}{dt}\] or            \[\left| e \right|=L\frac{di}{dt}\] Here, induced current \[=\frac{V}{R}\]                                 \[=\frac{10}{5}\]                                 = 2A Circuit switches off in 1 millisecond or            \[dt=1\times {{10}^{-3}}s\] and        \[L=10\,H\] \[\therefore \] Induced emf in inductor is                 \[\left| e \right|=10\times \frac{2}{1\times {{10}^{-3}}}\] \[=2\times {{10}^{4}}V\]


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