BCECE Engineering BCECE Engineering Solved Paper-2015

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

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

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

    C)  \[\frac{\pi }{2}\sqrt{LC}\]                           

    D) \[\frac{\pi }{6}\sqrt{LC}\]

    Correct Answer: B

    Solution :

    In LC oscillation, energy is transferred C to L or L to C, maximum energy in L is \[\frac{1}{2}LI_{\max }^{2}\] Maximum energy in C is  \[\frac{q_{\max }^{2}}{2C}\] Energy will be equal when, \[\frac{1}{2}L{{I}^{2}}=\frac{1}{2}\frac{1}{2}LI_{\max }^{2}\Rightarrow I=\frac{{{I}_{\max }}}{\sqrt{2}}\] \[I={{I}_{\max }}\sin \omega t=\frac{1}{\sqrt{2}}{{I}_{\max }}\] \[\omega t=\frac{\pi }{4}\Rightarrow \frac{2\pi }{T}t=\frac{\pi }{4}\Rightarrow t=\frac{T}{8}\] \[t=\frac{1}{8}2\pi \sqrt{LC}=\frac{\pi }{4}\sqrt{LC}\] \[\Rightarrow \]               \[t=\frac{\pi }{4}\sqrt{LC}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner