A point charge Q

Given,

R is the radius of the sphere and Q is a point charge

Formula used

We know that for a sphere or a point charge, the capacitance can be found out by the equation,

Now, to find energy stored, we have the relation,

Here the point charge has Q amount of charge and capacitance C is as given above. So by substitution,

Hence the expression for energy stored on a sphere around a point charge placed at the origin is Q²/8πε₀×R) J