A is the magnetic vector potential, φ is the electrostatic potential, His the magnetic field H, b is magnetic permeability. Although this equation is obviously a direct precursor of the modern Lorentz force equation, it actually differs in two respects • It does not contain a factor of q, the charge. Maxwell didn't use the concept of charge. The definition of E used hereby Maxwell is unclear. He uses the term electromotive force. He operated from Faraday's electro-tonic state A, which he considered to be a momentum in his vortex sea. The closest term that we can trace to electric charge in Maxwell's papers is the density of free electricity, which appears to refer to the density of the aethereal medium of his molecular vortices and that gives rise to the momentum A. Maxwell believed that A was a fundamental quantity from which electromotive force can be derived. • The equation here contains the information that what we nowadays call E, which today can be expressed in terms of scalar and vector potentials according to The fact that E can be expressed this way is equivalent to one of the four modern Maxwell s equations, the Maxwell-Faraday equation. Despite its historical origins in the original set of eight Maxwell's equations, the Lorentz force is no longer considered to be one of "Maxwell's equations" as the term is currently used (that is, as reformulated by Heaviside. It now sits adjacent to Maxwell's equations as a separate and essential law.