A uniformly charged spherical shell of radius 10 cm has electrostatic potential 120 V at its surface. The potentials at the centre, at r = 5 cm, and at r = 15 cm respectively are:
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Question

A uniformly charged spherical shell of radius 10 cm has electrostatic potential 120 V at its surface. The potentials at the centre, at r = 5 cm, and at r = 15 cm respectively are:

G1 Physics · Accepted Answer

For a uniformly charged spherical shell, electrostatic potential is constant everywhere inside the shell and is equal to its surface value. Therefore, V(centre) = 120 V, V(r=5 cm) = 120 V. Outside the shell, V(r) = kQ/r. At the surface, kQ/R = 120 V. Thus at r=15 cm, V = 120(R/r) = 120(10/15) = 80 V. Hence the three potentials are 120 V, 120 V, 80 V. Correct option: B.