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JEE Main & Advanced Sample Paper JEE Main Sample Paper-34

  • question_answer
    Two magnets placed one above the other oscillate with a period of 6 sec. If one of them is reversed, the time period becomes 2 sec. The ratio of their magnetic moment is nearest to:

    A)  7/3                                       

    B)  5/4

    C)  7/4                                       

    D)  7/5

    Correct Answer: B

    Solution :

    Let the magnetic moment of the two magnets be \[{{M}_{1}}\] and \[{{M}_{2}}\]             Then, \[6=2\pi \,\sqrt{\frac{1}{({{M}_{1}}-{{M}_{2}})B}}\]             and \[2=2\pi \,\sqrt{\frac{1}{({{M}_{1}}+{{M}_{2}})B}}\]             \[\Rightarrow \,\,\frac{{{M}_{1}}+{{M}_{2}}}{{{M}_{1}}-{{M}_{2}}}={{\left( \frac{6}{2} \right)}^{2}}=9\]             \[\therefore \,\,\frac{{{M}_{1}}}{{{M}_{2}}}=\frac{5}{4}\].


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