BCECE Medical BCECE Medical Solved Papers-2001

  • question_answer
    Reactance of a capacitor of capacitance C \[\mu F\]for AC frequency \[\frac{400}{\pi }\] Hz is 25 D. The value of C is:

    A)  \[50\,\mu F\]

    B)  \[25\,\mu F\]

    C)  \[100\,\mu F\]

    D)  \[75\,\mu F\]

    Correct Answer: A

    Solution :

    Capacitive reactance of an AC circuit containing only capacitor with an AC source is,                 \[{{X}_{C}}=\frac{1}{\omega C}\] or            \[{{X}_{C}}=\frac{1}{2\pi f\,C}\] or            \[C=\frac{1}{2\pi \,f\,{{X}_{C}}}\] Here,     \[f=\frac{400}{\pi }Hz,\] \[{{X}_{C}}=25\,\,\Omega \]                 \[\therefore \] \[C=\frac{1}{2\pi \times \frac{400}{\pi }\times 25}=\frac{1}{2\times 400\times 25}\]                 \[=5\times {{10}^{-5}}F\] \[=50\,\mu F\]


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