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NEET Sample Paper NEET Sample Test Paper-34

  • question_answer
    A coil of number of turn N, radius R is carrying current I have the value of magnetic field \[{{B}_{0}}\] at the centre. The value of magnetic field at the axis of that coil at the point which is very far away (X>>R) from the centre is proportional to :-

    A)  \[\frac{1}{X}\]               

    B)  \[\frac{1}{{{X}^{2}}}\]

    C)  \[\frac{1}{{{X}^{3}}}\]                 

    D)  \[\frac{1}{{{X}^{4}}}\]

    Correct Answer: C

    Solution :

    \[{{B}_{axis}}=\frac{{{\mu }_{0}}NI{{R}^{2}}}{2{{({{X}^{2}}+{{R}^{2}})}^{3/2}}}\approx \frac{{{\mu }_{0}}NI{{R}^{2}}}{2{{X}^{3}}}\] here \[{{X}^{2}}+{{R}^{2}}\approx {{X}^{2}}\]


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