If on two concentric hollow spheres of radii $R$ and $r$ $(R < r)$,a total charge $Q$ is distributed such that their surface charge densities are equal,then the potential at their common centre is:

  • A
    $\frac{Q(R^2+r^2)}{4\pi\varepsilon_0(R+r)}$
  • B
    $\frac{QR}{R+r}$
  • C
    zero
  • D
    $\frac{Q(R+r)}{4\pi\varepsilon_0(R^2+r^2)}$

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