NEET Sample Paper NEET Sample Test Paper-51

  • question_answer A bar magnet of length 10 cm and having pole strength equal to \[{{10}^{-3}}\] A x m is kept in a magnetic field of \[4\pi \,\,\times \,\,{{10}^{-}}^{3}\] Tesla. It makes an angle \[30{}^\circ \] with the direction of the field. The torque acting on the magnet is \[\left( newton\text{ }\times \text{ }metre \right)\]-

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

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

    C) \[0.5\]                           

    D) \[\,50\]

    Correct Answer: A

    Solution :

    \[M=mL\] \[={{10}^{-}}^{3}\,\,\times \,\,0.1\] \[={{10}^{-4}}\] \[Torque\,\tau \,\,=\,\,MB\text{ }\sin 30{}^\circ \] \[={{10}^{-4}}\times 4\pi \times {{10}^{-3}}\times \frac{1}{2}\] \[=\,\,\,2\pi \times {{10}^{-}}^{7}\,N-m\]

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