Electric potential V at a point is the work done per unit positive charge by an external agent in bringing a test charge from infinity to that point against the electric field: V = $\frac{W_ext}{q_0}$ = -integral(E.dr) from infinity to the point. SI unit: volt (V) = $\frac{joule}{coulomb}$. Dimensional formula: [M $L^2$ T^(-3) A^(-1)]. For a point charge Q: V = $\frac{kQ}{r}$. Potential is a scalar — it has magnitude and sign but no direction. This makes it much easier to compute than E for complex charge distributions, since potentials add algebraically (not vectorially). Convention: V = 0 at infinity. The potential difference between two points A and B: $V_A$ - $V_B$ = -integral from A to B of E.dr = work done per unit charge in moving from B to A.