A point charge is kept at the centre of a metallic insulated spherical shell. Then:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → electric field inside the shell is zero
A metallic shell is a conductor. In electrostatic equilibrium the free charges of a conductor arrange themselves so that the electric field inside the conducting material is zero; otherwise the free electrons would keep moving.
The point charge q at the centre induces a charge −q on the inner surface of the shell. By Gauss’s law a Gaussian surface drawn inside the metal of the shell then encloses \( q + (-q) = 0 \) net charge, which is consistent with a zero field in the metal. Because the shell is insulated, an equal charge +q appears on the outer surface.
The field of the induced charge on the outer surface is not cancelled outside the shell, so the field outside is not zero (Option 1 is not the answer), and the potential is not zero because the charges are all of one sign on the outer surface (Option 4).
NCERT (2026-27):
Electrostatics of Conductors – “… In the static situation, when there is no current inside or on the surface of the conductor, the electric field is zero everywhere inside the conductor. This fact can be taken as the defining property of a conductor.”