JEE Main & Advanced Physics Alternating Current / प्रत्यावर्ती धारा Question Bank ac Circuits

  • question_answer
    In a circuit \[L,\,C\text{  and  }R\]are connected in series with an alternating voltage source of frequency \[f\]. The current leads the voltage by 45°. The value of \[C\] is [CBSE PMT 2005]

    A)            \[\frac{1}{2\pi f(2\pi fL+R)}\]

    B)            \[\frac{1}{\pi f(2\pi fL+R)}\]

    C)            \[\frac{1}{2\pi f(2\pi fL-R)}\] 

    D)            \[\frac{1}{\pi f(2\pi fL-R)}\]

    Correct Answer: A

    Solution :

               \[\tan \varphi =\frac{{{X}_{C}}-{{X}_{L}}}{R}\] Þ \[\tan {{45}^{o}}=\frac{\frac{1}{2\pi fC}-2\pi fL}{R}\] Þ \[C=\frac{1}{2\pi \,f(2\pi fL+R)}\]


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