Consider a metallic earth wire placed on the top of an electric transmission tower. When an electrostatically charged cloud looms over this transmission tower, the metallic wires develop an induced surface charge. The electrostatic equilibrium of the conductor ensures that the electric field outside the conductor is perpendicular to its surface; while it vanishes within the conductor. The electric field on the surface of this conductor can be calculated, assuming an infinitesimal cylindrical Gaussian surface through the conductor. Along the curved surface, the flux is zero, whereas, at the flat end, the flux equals electric field times area. Under the assumption that surface charge density is constant, the total charge enclosed by the flat Gaussian surface equals the surface charge density times the surface area. Applying Gauss' Law, the total flux equals the charge enclosed divided by the permittivity of the vacuum. Rearranging the terms, the magnitude of electric field at the conductor's surface is obtained. Hence, the electric field at the surface of the conductor is dependent only on its surface charge density.