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A radius of spherical charged shell is 10 cm and electric potential on its surface is 100 V, then the potential at 2 cm from the centre of the shell will be ________.

Asked in GUJCET 2024 · Potential of shells and spheres

• (1) 1 V
• (2) 100 V
• (3) 200 V
• (4) 0 V

Step-by-step solution

Why the other options are wrong

• (1) No single slip gives 1 V. Inside the shell the potential does not depend on the distance from the centre at all, so the 2 cm never enters the arithmetic. Sanity check: the potential everywhere inside is the surface value, 100 V.
• (3) No single slip gives 200 V. Even treating the shell as a point charge (V ∝ 1/r) would give 100×(10)/2 = 500 V, and that formula holds only outside the shell.
• (4) It is the field inside the shell that is zero, not the potential. Zero field means V does not change inside, so it keeps its surface value of 100 V.

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