JEE Main · 2019 · 11 Jan 2019 · Shift 1 · Electrostatics

The give graph shown variation (with distance r from centre) of:

Answer: (B)

Solution

Read the curve carefully: the quantity is flat for

r < R

and then falls off smoothly like

1/ r

for

r > R

. A uniformly charged spherical shell has zero field inside, so its potential inside is a non-zero constant

k Q / R

, and outside it behaves exactly as that of a point charge,

k Q / r

. A field, by contrast, would be zero inside and fall as

1/ r^{2}

outside, which does not match a non-zero plateau. The curve therefore represents the potential of a uniformly charged spherical shell.

JEE Main · 2019 · 11 Jan 2019 · Shift 1 · Single correct option