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JEE Main & Advanced Physics Wave Mechanics Question Bank Critical Thinking

  • question_answer
    A metal wire of linear mass density of 9.8 g/m is stretched with a tension of 10 kg weight between two rigid supports 1 metre apart. The wire passes at its middle point between the poles of a permanent magnet, and it vibrates in resonance when carrying an alternating current of frequency n. The frequency n of the alternating source is                                                                                               [AIEEE 2003]

    A)            25 Hz                                       

    B)            50 Hz

    C)            100 Hz                                     

    D)            200 Hz

    Correct Answer: B

    Solution :

                       In condition of resonance, frequency of a.c. will be equal to natural frequency of wire                    \[n=\frac{1}{2l}\sqrt{\frac{T}{m}}=\frac{1}{2\times 1}\sqrt{\frac{10\times 9.8}{9.8\times {{10}^{-3}}}}=\frac{100}{2}=50\]\[Hz\]


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