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A solid sphere of radius R is charged uniformly. At what distance from its surface is the electrostatic potential half of the potential at the centre? (a) R (b) R/2 (c) R/3 (d) 2R |
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Answer» Correct Answer is: (c) R/3 Using the expression of the previous question’s answer, for r = 0, potential at the centre = Vc = k 3Q/2R. We require a point where V = Vc/2 = k 3Q/4R. This point cannot lie inside the sphere where V ≥ k Q/R. Let the point lie outside the sphere, at a distance r from the centre. Then, V = k Q/r = k 3Q/4R or r = 4/3 R Distance from the surface = r - R = R/3. |
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