BCECE Engineering BCECE Engineering Solved Paper-2003

  • question_answer
    In   a   series   combination\[R=300\,\Omega ,\]\[\text{L=0}\text{.9H,}\]\[\text{C=2}\text{.0}\,\text{F,}\]\[\omega =1000\,\text{rad/s,}\]the impedance of the circuit is :

    A)  1300\[\Omega \]                            

    B)         900\[\Omega \]

    C)         500\[\Omega \]                              

    D)         400\[\Omega \]

    Correct Answer: C

    Solution :

    In series RLC circuit, the impedance of the circuit is given by \[Z=\sqrt{{{R}^{2}}+{{({{X}_{L}}-{{X}_{C}})}^{2}}}\] Also,      \[{{X}_{L}}=\omega L,{{X}_{C}}=\frac{1}{\omega C}\] \[\therefore \]  \[Z=\sqrt{{{R}^{2}}+{{\left( \omega L-\frac{1}{\omega C} \right)}^{2}}}\] Given,\[R=300\,\Omega ,\omega =1000\,rad/s,L=0.9H,\]                                 \[C=2.0\,\mu F=2\times {{10}^{-6}}F\]                 Hence,                 \[Z=\sqrt{{{(300)}^{2}}+{{\left( 1000\times 0.9-\frac{1}{1000\times 2\times {{10}^{-6}}} \right)}^{2}}}\] \[=\sqrt{9000+{{(900-500)}^{2}}}\] \[=\sqrt{90000+160000}\] \[=\sqrt{250000}\] \[=500\,\Omega \]


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