JCECE Medical JCECE Medical Solved Paper-2005

  • question_answer
    A circular coil carrying a current has a radius R. The ratio of magnetic induction at the centre of the coil and at a distance equal to \[\sqrt{3}R\]from the centre of the coil on the axis is:

    A)  1 : 1        

    B)  1 : 2

    C)  2 : 1        

    D)  8 : 1

    Correct Answer: D

    Solution :

     The magnetic field [B] at a distance \[x\] from the circular coil is given by \[B=\frac{{{\mu }_{0}}ni{{R}^{2}}}{2{{({{R}^{2}}+{{x}^{2}})}^{3/2}}}\] where R is radius of the coil. At centre,\[x=0;\] \[{{B}_{0}}=\frac{{{\mu }_{0}}ni}{2R}\] At \[x=\sqrt{3}R\] \[\therefore \] \[{{B}_{a}}=\frac{{{\mu }_{0}}ni{{R}^{2}}}{2{{({{R}^{2}}+3{{R}^{2}})}^{3/2}}}=\frac{{{\mu }_{0}}ni}{16R}\] Hence \[\frac{{{B}_{0}}}{{{B}_{a}}}=\frac{8}{1}\]


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