Find an expression for the potential at a point due to a point charge Q.

Explanation

Consider a charge + Q situated at point O and let us want to determine electric potential due to it at a point P situated at a distance r. Then, by definition potential is equal to amount of work done in order to bring unit +ve charge, without any acceleration, from `oo` to point P.
`:. V = W_(oo-p)= underset(oo)oversetrintvecE.vecdx= -undersetoooversetrintE dx = -undersetoooversetrintQ/(4pi epsi_0x^2)dx`
`=(Q)/(4pi epsi_0)[1/x]_oo^r = Q/(4pi epsi_0)[1/r-1/oo] = Q/(4pi epsi_0r)`