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KVPY2014PhysicsElectrostatics

Consider a spherical shell of radius R with a total charge + q uniformly spread on its surface (center of the chell 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 < R) , respectively. Magnitude of the work done in this process is :

Options

  1. A(Q+q)² / 4 ₀ a
  2. Bzero
  3. Cq² / 4 ₀ a
  4. DQq / 4 ₀ a

Correct answer

C. q² / 4 ₀ a

Step-by-step solution

W ₁= q ( KQ R ) W ₂= ( KQ R + kq a )(- q ) W = - kq ² a

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