JEE Main & Advanced Physics Alternating Current / प्रत्यावर्ती धारा Question Bank Critical Thinking

  • question_answer
    In the circuit shown in the figure, the ac source gives a voltage \[V=20\cos (2000\,t).\] Neglecting source resistance, the voltmeter and ammeter reading will be  [KCET (Engg.) 2002]

    A)            0V, 0.47A                               

    B)            1.68V, 0.47A

    C)            0V, 1.4 A                                

    D)            5.6V, 1.4 A

    Correct Answer: D

    Solution :

                       \[Z=\sqrt{{{(R)}^{2}}+{{({{X}_{L}}-{{X}_{C}})}^{2}};}\]                    \[R=10\,\Omega ,\,\,{{X}_{L}}=\omega L=2000\times 5\times {{10}^{-3}}=10\,\Omega \]                    \[{{X}_{C}}=\frac{1}{\omega C}=\frac{1}{2000\times 50\times {{10}^{-6}}}=10\,\Omega \,\,i.e.\,Z=10\,\Omega \]                    Maximum current \[{{i}_{0}}=\frac{{{V}_{0}}}{Z}=\frac{20}{10}=2A\]                    Hence \[{{i}_{rms}}=\frac{2}{\sqrt{2}}=1.4\,A\]            and \[{{V}_{rms}}=4\times 1.41=\,\]5.64 V


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