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AFMC AFMC Solved Paper-2010

  • question_answer
    Torques \[{{\tau }_{1}}\,and\,{{\tau }_{2}}\] are required for magnetic needle to remain perpendicular to the magnetic fields B1 and B2 at two different places. The ratio B1/B2 is

    A) \[\frac{{{\tau }_{2}}}{{{\tau }_{1}}}\]                                      

    B) \[\frac{{{\tau }_{1}}}{{{\tau }_{2}}}\]

    C) \[\frac{{{\tau }_{1}}+{{\tau }_{2}}}{{{\tau }_{1}}-{{\tau }_{2}}}\]                                                

    D) \[\frac{{{\tau }_{1}}-{{\tau }_{2}}}{{{\tau }_{1}}+{{\tau }_{2}}}\]

    Correct Answer: B

    Solution :

    Torque, \[\tau =MB\sin \theta \] \[{{\tau }_{1}}=M{{B}_{1}}\sin {{90}^{o}}=M{{B}_{1}}\] \[{{\tau }_{2}}=M{{B}_{2}}\sin {{90}^{o}}=M{{B}_{2}}\] or   \[\frac{M{{B}_{1}}}{M{{B}_{2}}}=\frac{{{\tau }_{1}}}{{{\tau }_{2}}}\] \[\therefore \]  \[\frac{{{B}_{1}}}{{{B}_{2}}}=\frac{{{\tau }_{1}}}{{{\tau }_{2}}}\]


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