High Quality Content by WIKIPEDIA articles! The retarded potential formulae describe the scalar or vector potential for electromagnetic fields of a time-varying current or charge distribution. The retardation between cause and effect is thereby essential; e.g. the signal takes a finite time, corresponding to the velocity of light, to propagate from the source point mathbf r', of the field to the point mathbf r,, where an effect is produced or measured. Otherwise, the formulas below correspond to the same superposition principle acting, e.g., in electrostatics for Coulomb's law. Coulomb's law is a law of physics describing the electrostatic interaction between electrically charged particles. It was studied and first published in 1783 by French physicist Charles Augustin de Coulomb and was essential to the development of the theory of electromagnetism. Nevertheless, the dependence of the electric force with distance (inverse square law) had been proposed previously by Joseph Priestley and the dependence with both distance and charge had been discovered, but not published, by Henry Cavendish, prior to Coulomb's works.