Q 12-02-208JEE MainJEE Main 2025 (3 Apr, Shift 1)Easy
The electrostatic potential on the surface of a uniformly charged spherical shell of radius $R = 10\ \text{cm}$ is $120\ \text{V}$. The potentials at the centre of the shell, at a distance $r = 5\ \text{cm}$ from the centre, and at a distance $r = 15\ \text{cm}$ from the centre of the shell respectively, are:
Answer: (A) $120\ \text{V},\ 120\ \text{V},\ 80\ \text{V}$
Inside a charged shell the field is zero, so the potential everywhere inside equals the surface value: $120\ \text{V}$ at the centre and at $r = 5\ \text{cm}$.
Outside, $V = \dfrac{kQ}{r}$ with $\dfrac{kQ}{R} = 120\ \text{V}$:
$$V(15\ \text{cm}) = 120\times\frac{10}{15} = 80\ \text{V}$$
Solution by Sreeraj P, M.Sc Physics