An isolated solid conductor in electrostatic equilibrium carries a uniform positive surface charge density \(\sigma\). The electric field just outside the surface of the conductor has magnitude \(E = \dfrac{\sigma}{\varepsilon_0}\) and points perpendicular to the surface. Which of the following correctly states the magnitude of the electrostatic force \(dF\) exerted on a small patch of area \(dA\) by all the other charges on the conductor, and provides the correct physical justification?