Q.A hollow metal ball carrying an electric charge produces no electric field at points :

For a hollow spherical shell of radius R carrying total charge Q spread uniformly over its surface, Gauss's law with a concentric spherical Gaussian surface gives two distinct regimes. Outside the shell (Gaussian radius r greater than R), the enclosed charge is the full Q, and spherical symmetry makes the field constant in magnitude and radial everywhere on the Gaussian sphere, giving E(4 pi r^2) = Q/epsilon0, so E = kQ/r^2 -- identical to the field of an equal point charge Q placed at the centre, even though the real charge is spread out over the shell's surface rather than concentrated at a point. Inside the shell (Gaussian radius r less than R), the enclosed charge is exactly zero, since none of the shell's actual charge lies within a sphere sm …