JEE Main & Advanced Physics Magnetism Question Bank Magnet and its Properties

  • question_answer
    A bar magnet of length 10 cm and having the pole strength equal to 10?3 weber is kept in a magnetic field having magnetic induction  equal to \[4\pi \times {{10}^{-3}}\]Tesla. It makes an angle of 30o with the direction of magnetic induction. The value of the torque acting on the magnet is            [MP PMT 1993]

    A)            \[2\pi \times {{10}^{-7}}N\times m\]                            

    B)            \[2\pi \times {{10}^{-5}}N\times m\]

    C)            \[0.5N\times m\]               

    D)            \[0.5\times {{10}^{2}}N\times m\] (\[{{\mu }_{0}}=4\pi \times {{10}^{-7}}weber/amp\times m\])

    Correct Answer: A

    Solution :

                       Torque \[\tau =M{{B}_{H}}\sin \theta \]                    \[=0.1\times {{10}^{-3}}\times 4\pi \times {{10}^{-3}}\times \sin {{30}^{o}}={{10}^{-7}}\times 4\pi \times \frac{1}{2}\]            \[=2\pi \times {{10}^{-7}}N\times m\]


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