Electrostatic Potential and Capacitance — Class 12 Physics

Electrostatic potential at a point is the work done per unit positive charge in bringing it from infinity to that point, for a point charge. Potential is a scalar, making it easier to handle than the field, and the two are linked by ; the field always points from high to low potential. Equipotential surfaces, on which is constant, are everywhere perpendicular to field lines, and no work is done moving a charge along them. The electrostatic potential energy of a charge configuration is the total work done in assembling it. A conductor in equilibrium has zero field inside and a constant potential throughout, with charge residing on its surface. Dielectrics, when polarised, reduce the field inside by a factor of the dielectric constant. A capacitor stores charge and energy; its capacitance depends only on geometry and the dielectric. For a parallel-plate capacitor , increased times by a dielectric. Capacitors in series and parallel combine by reciprocal and direct sums respectively, and the energy stored is , residing in the field between the plates.