BHU PMT BHU PMT Solved Paper-2003

  • question_answer
    An L-C circuit is in the state of resonance. If\[C=0.1\,\,\mu F\]and\[L=0.25\,\,H\], neglecting ohmic resistance of circuit. What is the frequency of oscillations?                                 [BHU M-2003]

    A)  \[1007\,\,Hz\]                  

    B)  \[100\,\,Hz\]

    C)  \[109\,\,Hz\]                                    

    D)  \[500\,\,Hz\]

    Correct Answer: A

    Solution :

                     Key Idea: In the state of resonance inductive and capacitive reactance?s are equal. \[{{X}_{L}}={{X}_{C}}\] \[\Rightarrow \]                               \[\omega L=\frac{1}{\omega C}\] \[\Rightarrow \]                               \[2\pi fL=\frac{1}{2\pi fC}\] \[\Rightarrow \]                               \[{{f}^{2}}=\frac{1}{4{{\pi }^{2}}LC}\] \[\Rightarrow \]                               \[f=\frac{1}{2\pi }\sqrt{\frac{1}{LC}}\] \[\left( resonant\,\,frequency \right)\] Given, \[L=0.25\,\,H,\]\[C=0.1\,\mu \,F=0.1\times {{10}^{-6}}\,F\]                 \[\therefore \]                  \[f=\frac{1}{2\pi }\sqrt{\frac{1}{0.25\times 0.1\times {{10}^{-6}}}}\]                                                                 \[f=1007\,\,Hz\]


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