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NEET Sample Paper NEET Sample Test Paper-89

  • question_answer
    A coil in the shape of an equilateral triangle of side \[l\] is suspended between the pole pieces of a permanent magnet such that \[\overrightarrow{B}\] is in plane of the coil. If due to a current i in the triangle a torque\[\tau \] acts on it, the side \[l\] of the triangle is

    A) \[\frac{2}{\sqrt{3}}{{\left( \frac{\tau }{Bi} \right)}^{\frac{1}{2}}}\]                   

    B) \[\frac{2}{3}\left( \frac{\tau }{Bi} \right)\]

    C) \[2{{\left( \frac{\tau }{\sqrt{3}Bi} \right)}^{\frac{1}{2}}}\]         

    D)        \[\frac{1}{\sqrt{3}}\frac{\tau }{Bi}\]

    Correct Answer: C

    Solution :

    [c] Torque \[(\tau )\] on the triangle \[=M\times B\] \[\tau =i\frac{1}{2}\ell .\ell .\sin 60.\]\[B=\frac{1}{2}{{\ell }^{2}}.\frac{\sqrt{3}}{2}Bi\] \[\ell =\sqrt{\frac{4\tau }{\sqrt{3}Bi}}=2{{\left( \frac{\tau }{\sqrt{3}Bi} \right)}^{\frac{1}{2}}}\]


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