The electrostatic potential on the surface of uniformly charged spherical shell of radius R = 10 cm is 120 V. The potential at the centre of shell, at a distance r = 5 cm from centre, and at a distance r = 15 cm from the centre of the shell respectively, are: (a) 0 V, 120 V, 40 V (b) 120 V, 120 V, 80 V (c) 40 V, 40 V, 80 V (d) 0 V, 0 V, 80 V

Answer: (b). Inside the shell ( r ≤ R): V = Vsurface = 120 V, so at the centre and at 5 cm it is 120 V. Outside: V ∝ 1/r ⇒ V(15) = 120 × 10/15 = 80 V So the answer is (b) 120 V, 120 V, 80 V.

The electrostatic potential on the surface of uniformly charged… | JEE Main 2025 (3 Apr, Shift 1)

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Electric Potential & Equipotentials

The electrostatic potential on the surface of uniformly charged spherical shell of radius $R = 10\text{ cm}$ is 120 V. The potential at the centre of shell, at a distance $r = 5\text{ cm}$ from centre, and at a distance $r = 15$ cm from the centre of the shell respectively, are:

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Answer: (b)

Inside the shell ( $r \le R$ ): $V = V_{\text{surface}} = 120\text{ V}$ , so at the centre and at 5 cm it is 120 V.
Outside: $V \propto \frac{1}{r} \Rightarrow V(15) = 120 \times \frac{10}{15} = 80\text{ V}$
So the answer is (b) $120\text{ V}, 120\text{ V}, 80\text{ V}$ .

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