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BCECE Engineering BCECE Engineering Solved Paper-2008

  • question_answer
    A bar magnet when placed at an angle of \[{{30}^{o}}\] the direction of magnetic field induction of \[5\times {{10}^{-2}}T,\]experiences a moment of couple \[25\times {{10}^{-6}}\,N-m.\] If the length of the magnet is 5 cm its pole strength is

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

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

    C)         \[2\,A-m\]        

    D)         \[5\,A-m\]

    Correct Answer: A

    Solution :

    \[\tau =MB\sin \theta \] \[\Rightarrow \]\[\tau =(mL)Bsin\theta \] \[\Rightarrow \]\[25\times {{10}^{-6}}=(m\times 5\times {{10}^{-2}})\times 5\times {{10}^{-2}}\times \sin {{30}^{o}}.\]       \[\Rightarrow \]\[m=2\times {{10}^{-2}}\,A-m\]


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