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

  • question_answer
    An LC circuit contains a 20 mH inductor and a \[25\text{ }\mu \text{F}\] capacitor with an initial charge of 5 mC. The total energy stored in the circuit initially is:

    A) 5 J                   

    B) 0.5 J   

    C) 50 J                             

    D) 500 J

    Correct Answer: B

    Solution :

    (b) 0.5 J Here,    \[C=25\,\mu F=25\times {{10}^{-6}}F,\] \[L=20\,mH=20\times {{10}^{-3}}H,{{q}_{0}}=5\,mC=5\times {{10}^{-3}}C\] Total energy stored in the circuit initially is \[U=\frac{q_{0}^{2}}{2C}=\frac{{{\left( 5\times {{10}^{-3}} \right)}^{2}}}{2\times 25\times {{10}^{-6}}}\] \[=\frac{25\times {{10}^{-6}}}{2\times 25\times {{10}^{-6}}}=\frac{1}{2}=0.5\,J\]


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