A battery is connected between two points $A$ and $B$ on the circumference of a uniform conducting ring of radius $r$ and resistance $R$. One of the arcs $AB$ of the ring subtends an angle $\theta $ at the centre. The value of the magnetic induction at the centre due to the current in the ring is

  • [IIT 1995]
  • A

    Proportional to $2\,(180^\circ - \theta )$

  • B

    Inversely proportional to $r$

  • C

    Zero, only if $\theta = 180^\circ $

  • D

    Zero for all values of $\theta $

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