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JEE Main & Advanced Physics Magnetism Question Bank Self Evaluation Test - Magnetism and Matter

  • question_answer
    If the period of oscillation of freely suspended bar magnet in earth's horizontal field H is 4 sec. When another magnet is brought near it, the period of oscillation is reduced to 2s. The magnetic field of second bar magnet is

    A) 4H  

    B) 3H  

    C) 2H  

    D) \[\sqrt{3}H\]

    Correct Answer: A

    Solution :

    [a] Thus,  \[\frac{T}{T'}=\frac{2\pi \sqrt{\frac{I}{MH}}}{2\pi \sqrt{\frac{I}{MH'}}}\] Given,  \[T=4\,\sec \], \[T'=2\sec \], So, \[\frac{4}{2}=\sqrt{\frac{H'}{H}}\Rightarrow H'=4H\]


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