Abstract

In 1832, Faraday assumed the induction between magnet and conductor produced the induced electromotive force (e.m.f.) dU in the conductor. In 1834, Lentz considered the induction produced the induced current I in the conductor. The above are all induced matters with different causal relation. In 1865, Maxwell assumed during the magnet motion vortex electric-field (E-field) was produced around free space, which seemed to end the dispute of causal relation and yet it brought forward the question that the induction was produced in the conductor or in free space? In 1892, Lorentz created a metal electronic theory, for this reason the metal electron caused the induced current under Lorentz magnetic force, in which the nature is force F instead of field. In essence, whether coil motion or magnet motion, as long as the relative movement remains between magnetic field and conductor, the metal electron will inevitably cut the magnetic line. The essence of electromagnetic induction could be consequently integrated with Lorentz magnetic force. In early twentieth century, relative electromagnetic theory arose that included electric field E and magnetic field B. So far, the unified theory on the electromagnetic induction nature has been not established. Which is nature, which is phenomenon? Which is reason? Which is result? Which is truth? Which is mistake? It is a great problem for all of us.