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MHT CET 2021 (20 Sep, Shift 1) · Electric Flux & Gauss's Law

Electric Flux & Gauss's Law question from MHT CET 2021 (20 Sep, Shift 1)

Q89MHT CET 2021 · 20 SEP · SHIFT 1Medium

Electric Flux & Gauss's Law

A spherical conducting shell of inner radius 'r 1{}_{1}' and outer radius 'r2{}_{2} ' has a charge 'Q'. A charge −-q is placed at the centre of the shell. The surface charge density on the inner and outer surface of the shell will be

Figure

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Answer: (a)

  1. Field inside the conductor is zero, so the inner surface carries +q+q to cancel the central −q-q.
  2. Total shell charge is QQ, so the outer surface carries Q−qQ - q.
  3. σin=q4πr12\sigma_{in} = \frac{q}{4\pi r_1^2}, σout=Q−q4πr22\sigma_{out} = \frac{Q - q}{4\pi r_2^2}
  4. So the answer is (a).
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