Which one of the following statements is INCORRECT about electrostati…

The correct answer is Option (3) → The electrostatic potential vanishes throughout the volume of the charged conductor.

In electrostatic equilibrium the free charges in a conductor are at rest, so there is no field inside it and no field component along its surface.

Option (1) Electrostatic field is zero inside a conductor. — Correct. Any field inside would move the free electrons, so E = 0 inside.

Option (2) The electrostatic field at the surface of a charged conductor must be normal to surface at every point. — Correct. A tangential component would move charges along the surface.

Option (3) The electrostatic potential vanishes throughout the volume of the charged conductor. — Incorrect. E = 0 inside means the potential is constant throughout the conductor, equal to its surface value, not zero.

Option (4) The interior of a conductor can have no excess charge in the static situation. — Correct. By Gauss’s law a closed surface inside encloses zero charge, so any excess charge resides on the surface.

NCERT (2026-27):
Electrostatics of Conductors – “… In the static situation, the free charges have so distributed themselves that the electric field is zero everywhere inside. Electrostatic field is zero inside a conductor. … Thus electrostatic field at the surface of a charged conductor must be normal to the surface at every point. … This means there is no net charge at any point inside the conductor, and any excess charge must reside at the surface. … That is, there is no potential difference between any two points inside or on the surface of the conductor.”