RAJASTHAN ­ PET Rajasthan PET Solved Paper-2005

  • question_answer
    The intensity of magnetic field of a current carrying circular at a point on its axis at distance \[x(x>>R)\]will depends upon

    A)  \[B\alpha \frac{1}{{{x}^{3/2}}}\]        

    B)  \[B\alpha \frac{1}{{{x}^{2}}}\]

    C)  \[B\alpha \frac{1}{{{x}^{3}}}\]        

    D)  \[B\alpha \frac{1}{{{x}^{1/2}}}\]

    Correct Answer: C

    Solution :

     \[B=\frac{{{\mu }_{0}}NI{{R}^{2}}}{2{{({{R}^{2}}+{{x}^{2}})}^{3/2}}}\] Here, \[x>>R\]   \[(\therefore {{R}^{2}}+{{x}^{2}}={{x}^{2}})\] \[\therefore \] \[B=\frac{{{\mu }_{0}}NI{{R}^{2}}}{2{{x}^{3}}}\] Or \[B=\frac{1}{{{x}^{3}}}\]


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