BCECE Medical BCECE Medical Solved Papers-2004

  • question_answer
    If the potential of a capacitor having capacity 6 \[\mu F\]is increased from 10 V to 20V, then increase in its energy is :

    A) \[12\times {{10}^{-6}}J\]

    B) \[9\times {{10}^{-4}}J\]

    C)  \[4.5\times {{10}^{-6}}J\]

    D)  \[2.25\times {{10}^{-6}}J\]

    Correct Answer: B

    Solution :

    In capacitor, energy is .stored in electric field between the plates. Increase in energy                 \[\Delta U={{U}_{f}}-{{U}_{i}}\]                 \[=\frac{1}{2}C\,({{V}_{f}}^{2}-V_{i}^{2})\]                 \[=\frac{1}{2}C\,({{V}_{f}}^{2}-V_{i}^{2})\] Given,   \[C=6\,\mu F=6\times {{10}^{-6}},{{V}_{i}}=10\] volt,                 \[{{v}_{f}}=20\] volt \[\therefore \] \[\Delta U=\frac{1}{2}\times 6\times {{10}^{-6}}[{{(20)}^{2}}-{{(10)}^{2}}]\]                 \[=3\times {{10}^{-6}}\times 300\] \[=9\times {{10}^{-4}}J\]


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