A metal sphere of radius R is charged to a pontital V . (a ) Find the electrostatic energy stored in the electric field within a concentric sphere of radius 2 R . (b )Show that the electrostatic field energy stored outside the sphere of radius 2R equals that stored within it .

Explanation

Potential `= V `,
Capacitance `(= 4 pie eplison_0) R . 2 . R / 2 R - R `
`= 4 pie eplison _0 2R`
`(V_2 = 1 / 4 pie eplsion _0) q / 2 R = V / 2`
So, energy `= 1 / 2 C (v - v_2)^(2) `
`= 1 / 0 xx 4 pie eplsion_0 2 R xx V^(2) / 4 `
`= pie eplison_0 RV^(2)`