JCECE Engineering JCECE Engineering Solved Paper-2011

  • question_answer
    A current of \[1\,\,A\] flows in a circular area of wire which subtends an angle of \[\left( \frac{3\pi }{4} \right)rad\] at its centre, whose radius is\[R\]. The magnetic induction \[B\] at the centre is

    A) \[\frac{{{\mu }_{0}}I}{R}\]                                           

    B)  \[\frac{{{\mu }_{0}}I}{2R}\]

    C)  \[\frac{2{{\mu }_{0}}I}{R}\]                       

    D)  \[\frac{3{{\mu }_{0}}I}{8R}\]

    Correct Answer: D

    Solution :

    For a loop, magnetic induction at centre                 \[B=\frac{{{\mu }_{0}}}{4\pi }\times \frac{2\pi I}{R}\] When loop subtends angle\[\theta \] at centre, then                 \[B=\frac{{{\mu }_{0}}}{4\pi }\times \frac{\theta I}{R}\] In the given problem\[\theta =\frac{3\pi }{2}\] \[\therefore \]  \[B=\frac{{{\mu }_{0}}}{4\pi }\times \frac{3\pi }{2}\times \frac{I}{R}\]                 \[=\frac{3{{\mu }_{0}}I}{8R}\]


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