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JEE Main & Advanced Sample Paper JEE Main - Mock Test - 44

  • question_answer
    A short magnet produces a deflection of \[30{}^\circ \] when placed at certain distance in \[tanA\]position of magnetometer. If another short magnet of double the length and thrice the pole strength is placed at the same distance in \[tanB\] position of the magnetometer, the deflection produced will be -

    A) \[60{}^\circ \]          

    B)        \[30{}^\circ \]

    C) \[45{}^\circ \]              

    D)        None

    Correct Answer: A

    Solution :

      [a] In \[tan\,A\] position, \[\frac{{{\mu }_{0}}}{4\pi }\frac{2M}{{{d}^{3}}}={{B}_{H}}\tan 30{}^\circ =\frac{{{B}_{H}}}{\sqrt{3}}\]            ??..(1) Magnetic moment of second magnet, \[{M}'=(3m)(2\times 2\ell )=6M\] In tan B position, \[\frac{{{\mu }_{0}}}{4\pi }\frac{6M}{{{d}^{3}}}={{B}_{H}}\tan \theta \]                  ?.....(2) dividing eq. (2) by (1) we get \[\frac{6}{2}=\frac{\tan \theta }{1/\sqrt{3}}\] or \[tan\,\theta =\sqrt{3}\]  or  \[\theta =60{}^\circ \] 


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