A Helmholtz coil has pair of loops, each with $N$ turns and radius $R$. They are placed coaxially at distance $R$ and the same current $I$ flows through the loops in the same direction. The magnitude of magnetic field at $P$, midway between the centres $A$ and $C$, is given by (Refer to figure)

821-569

  • [JEE MAIN 2018]
  • A

    $\frac{{4N{\mu _0}I}}{{{5^{3/2}}R}}$

  • B

    $\frac{{8N{\mu _0}I}}{{{5^{3/2}}R}}$

  • C

    $\frac{{4N{\mu _0}I}}{{{5^{1/2}}R}}$

  • D

    $\frac{{8N{\mu _0}I}}{{{5^{1/2}}R}}$

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