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12th Class Physics Alternating Current / प्रत्यावर्ती धारा Question Bank MCQ - Alternating Currents

  • question_answer
    An LC-circuit contains 10 mH inductor and 25 mF capacitor with given initial charge. The resistance of the circuit is negligible. The energy stored in circuit is completely magnetic at time (in millisecond) the time is measured from the instant when the circuit is closed:

    A) \[0,\frac{\pi }{2},\frac{2\pi }{2},...etc\]   

    B) \[\frac{\pi }{3},\frac{2\pi }{3},\frac{5\pi }{3},...etc.\]

    C) \[\frac{\pi }{4},\frac{3\pi }{4},\frac{5\pi }{5},...etc\]       

    D) \[0,\frac{\pi }{8},\frac{\pi }{4},...etc.\]

    Correct Answer: C

    Solution :

    (c) \[\frac{\pi }{4},\frac{3\pi }{4},\frac{5\pi }{5},...etc\] [at \[t=0,\frac{T}{2},T,\frac{3T}{2}...\]energy is electrostatic and at \[t=\frac{T}{4},\frac{3T}{4},\frac{5T}{4}...\]energy is totally magnetic.  Here, \[T=\frac{1}{v}=2\pi \sqrt{LC}=\pi /1000\]]


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