JEE Main · 2025 · 03 Apr 2025 · Shift 1 · Electrostatics

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) $120 V, 120 V, 80 V$ ✓ Correct
(B) $40 V, 40 V, 80 V$
(C) $0 V, 0 V, 80 V$
(D) $0 V, 120 V, 40 V$

Answer: (A)

Solution

Inside a uniformly charged spherical shell the field is zero, so the potential is constant throughout and equal to its surface value. Hence at the centre and at

r = 5 cm

, both inside the

R = 10 cm

shell, the potential is

120 V

. Outside the shell the potential falls as

1/ r

V = \frac{V _{R} R}{r} = \frac{120 \times 10}{15} = 80 V at r = 15 cm .

The three potentials are

120 V

120 V

and

80 V

JEE Main · 2025 · 03 Apr 2025 · Shift 1 · Single correct option

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