Ampere’s Law, relating a steady electric current to a circulating magnetic field, was well known by the time James Clerk Maxwell started his research in a similar field in the 1850s. Although Ampere’s Law was known to apply only to static situations involving steady currents, it was Maxwell’s effort to add another source term—a change of electric flux—that extended the applicability of Ampere’s Law to time-dependent conditions. More important, it was the presence of this term in Ampere’s equation that led to it being known as Ampere-Maxwell’s Law. It allowed Maxwell to distinguish the electromagnetic nature of light and to develop a comprehensive theory of electromagnetism [1].