Consider a thin spherical shell of radius R carrying charge Q. To find the electric field outside the shell, we consider a spherical Gaussian surface of radius r (> R), concentric with given shell. The electric field vector E is same at every point of Gaussian surface and directed radially outwards (as is unit vector n so that q = 0°)
According to Gauss’s theorem,
Hence, electric field outside a charged thin spherical shell is the same as if the whole charge Q is concentrated at the centre.
The variation of electric field vector E with distance from centre of a uniformly charged spherical shell is shown in figure.