The electric potential V at a point is the work done per unit charge in bringing a small positive test charge from infinity to that point. It is measured in volts, where 1 V = 1 J C-1, and the potential at infinity is defined as zero.For an isolated point charge Q, the potential at a distance r is V = Q/(4πε0r). Unlike gravitational potential, electric potential can be positive or negative. It is positive near a positive charge, because work must be done to push a positive charge towards it, and negative near a negative charge.
Electric potential is a scalar, so the potential due to several charges is found by adding the individual potentials, including their signs. It varies inversely with distance, not with the square of the distance.The electric field strength equals the negative of the potential gradient, E = -ΔV/Δr. On a graph of V against r, the gradient of the tangent at any point gives the field strength at that distance.The electric potential energy of a charge q at a point is qV, so for two point charges E = Qq/(4πε0r). The work done in moving a charge q between two points is qΔV.
Electric potential is a scalar, so the potential due to several charges is found by adding the individual potentials, including their signs. It varies inversely with distance, not with the square of the distance.The electric field strength equals the negative of the potential gradient, E = -ΔV/Δr. On a graph of V against r, the gradient of the tangent at any point gives the field strength at that distance.The electric potential energy of a charge q at a point is qV, so for two point charges E = Qq/(4πε0r). The work done in moving a charge q between two points is qΔV.