The magnetic induction at the centre $O$ in the figure shown is

128-18

  • [IIT 1988]
  • A

    $\frac{{{\mu _0}i}}{4}\left( {\frac{1}{{{R_1}}} - \frac{1}{{{R_2}}}} \right)$

  • B

    $\frac{{{\mu _0}i}}{4}\left( {\frac{1}{{{R_1}}} + \frac{1}{{{R_2}}}} \right)$

  • C

    $\frac{{{\mu _0}i}}{4}({R_1} - {R_2})$

  • D

    $\frac{{{\mu _0}i}}{4}({R_1} + {R_2})$

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