Consider a spherical shell of radius $R$ with a total charge $+Q$ uniformly spread on its surface (centre of the shell lies at the origin $x=0$). Two point charges $+q$ and $-q$ are brought,one after the other,from far away and placed at $x=-a/2$ and $x=+a/2$ $(a < 2R)$,respectively. The magnitude of the work done in this process is:

  • A
    $(Q+q)^2 / 4 \pi \varepsilon_0 a$
  • B
    zero
  • C
    $q^2 / 4 \pi \varepsilon_0 a$
  • D
    $Q q / 4 \pi \varepsilon_0 a$

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