JEE Main & Advanced Physics EM Waves JEE PYQ-Electro Magnetic Waves

  • question_answer
    A fully charged capacitor C with initial charge \[{{q}_{0}}\] is connected to a coil of self-inductance L at \[t=0\]. The time at which the energy is stored equally between the electric and the magnetic fields is [AIEEE 2011]

    A) \[\sqrt{LC}\]

    B) \[\pi \sqrt{LC}\]

    C) \[\frac{\pi }{4}\sqrt{LC}\]

    D) \[2\pi \sqrt{LC}\]

    Correct Answer: C

    Solution :

    [c] \[q={{q}_{0}}\cos \omega \,t\] energy is halved when \[q=\frac{{{q}_{0}}}{\sqrt{2}}\]
    \[\Rightarrow \omega \,t=\frac{\pi }{4}\]
    \[\Rightarrow \,\frac{1}{\sqrt{LC}}t=\frac{\pi }{4}\]
    \[\Rightarrow \,t=\frac{\pi }{4}\sqrt{Lc}\]


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