Question:
A metal sphere of radius $\mathrm{R}$ is charged to a potential $\mathrm{V}$.
(a) Find the electrostatic energy stored in the electric field within a concentric sphere of radius $2 \mathrm{R}$.
(b) Show that the electrostatic field energy stored outside the sphere of radius $2 \mathrm{R}$ equals that stored within it.
Solution:
hence proved