RAJASTHAN PMT Rajasthan - PMT Solved Paper-2008

  • question_answer
    In an oscillating LC circuit the maximum charge on the capacitor is\[Q.\]The charge on the capacitor when the energy is stored equally between the electric and magnetic fields is

    A)  \[Q/2\]                               

    B)  \[Q/\sqrt{3}\]

    C)  \[Q/\sqrt{2}\]                  

    D)         \[Q\]

    Correct Answer: C

    Solution :

    In an \[LC\] circuit the energy oscillates between inductor (in the magnetic field) and capacitor (in the electric field). \[{{U}_{E\,\,\max }}\][Maximum energy stored in capacitor]                 \[=\frac{{{Q}^{2}}}{2C}\] \[{{U}_{B\,\,\max }}\][Maximum energy stored in inductor]                 \[=\frac{Li_{0}^{2}}{2}\] where \[{{I}_{0}}\] is the current at this time. For the given instant\[{{U}_{E}}={{U}_{B}}\] \[ie,\]    \[\frac{{{q}^{2}}}{2C}=\frac{L{{i}^{2}}}{2}\] From energy conservation                 \[{{U}_{E}}+{{U}_{B}}={{U}_{E\,\,\max }}={{U}_{B\,\,\max }}\] \[\Rightarrow \]               \[2\frac{{{q}^{2}}}{2C}=\frac{{{Q}^{2}}}{2C}\] \[\Rightarrow \]               \[q=\frac{Q}{\sqrt{2}}\]


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