A charge $+q$ is distributed over a thin ring of radius $r$ with line charge density $\lambda=q \sin ^{2} \theta /(\pi r)$. Note that the ring is in the $X Y$ - plane and $\theta$ is the angle made by $r$ with the $X$-axis. The work done by the electric force in displacing a point charge $+ Q$ from the centre of the ring to infinity is

  • [KVPY 2019]
  • A

    equal to $q Q / 2 \pi \varepsilon_{0} r$

  • B

    equal to $q Q / 4 \pi \varepsilon_{0} r$

  • C

    equal to zero only, if the path is a straight line perpendicular to the plane of the ring

  • D

    equal to $q Q / 8 \pi \varepsilon_{0} r$

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