VIT Engineering VIT Engineering Solved Paper-2010

  • question_answer
    Magnetic field at the center of a circular loop of area A is B. The magnetic moment of the loop will be

    A)  \[\frac{B{{A}^{2}}}{{{\mu }_{0}}\pi }\]

    B)  \[\frac{B{{A}^{3/2}}}{{{\mu }_{0}}\pi }\]

    C)  \[\frac{B{{A}^{3/2}}}{{{\mu }_{0}}{{\pi }^{1/2}}}\]

    D)  \[\frac{2B{{A}^{3/2}}}{{{\mu }_{0}}{{\pi }^{1/2}}}\]

    Correct Answer: D

    Solution :

    \[B=\frac{{{\mu }_{0}}}{4\pi }\frac{2\pi i}{r}=\frac{{{\mu }_{0}}i}{2r}\] or \[i=\frac{2Br}{{{\mu }_{0}}}\] Also,    \[A=\pi {{r}^{2}}\] or \[r={{\left( \frac{A}{\pi } \right)}^{1/2}}\] Magnetic moment, \[M=iA=\frac{2Br}{\mu {{ & }_{0}}}A\] \[=\frac{2BA}{{{\mu }_{0}}}\times {{\left( \frac{A}{\pi } \right)}^{1/2}}\] \[=\frac{2B{{A}^{3/2}}}{{{\mu }_{0}}{{\pi }^{1/2}}}\]  


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