Two small equal point charges of magnitude $q$ are suspended from a common point on the ceiling by insulating mass less strings of equal lengths. They come to equilibrium with each string making angle $\theta $ from the vertical. If the mass of each charge is $m,$ then the electrostatic potential at the centre of line joining them will be $\left( {\frac{1}{{4\pi { \in _0}}} = k} \right).$
  • A$2\sqrt {k\,\,mg\,\,\tan \theta } $
  • B$\sqrt {k\,\,mg\,\,\tan \theta } $
  • C$4\sqrt {k\,\,mg/\tan \theta } $
  • D$6\sqrt {k\,\,mg/\tan \theta } $
JEE MAIN 2013, Diffcult
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