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

  • question_answer
    A magnet of magnetic moment  \[50\,\hat{i}\,A\text{-}{{m}^{2}}\] is placed along the x-axis in a magnetic field \[\overrightarrow{B}=(0.5\,\hat{i}+3.0\hat{j})\,T.\] The torque acting on the magnet is [MP PMT 2000]

    A)            175 \[\hat{k}\,\,N\text{-}m\]                                           

    B)            150 \[\hat{k}\,\,N\text{-}m\]

    C)            75 \[\hat{k}\,\,N\text{-}m\] 

    D)            \[25\sqrt{37}\,\hat{k}\,\,N\text{-}m\]

    Correct Answer: B

    Solution :

                       \[\overrightarrow{\tau }=\overrightarrow{M}\times \overrightarrow{B}\Rightarrow \overrightarrow{\tau }=50\hat{i}\times (0.5\hat{i}+3\hat{j})\]            \[=150\left( \hat{i}\times \hat{j} \right)=150\hat{k}N\times m.\]


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