Unipolar Induction Revisited: New Experiments and the “Edge Effect” Theory

摘要

A brief historical review is made of the 180-year-old debate on Faraday’s unipolar inductor. By introducing two convenient modifications of Faraday’s original experiment of 1832, pertinent answers are experimentally found to the most debated problems: 1) Can Faraday’s law be used? Yes; 2) Do the magnetic field lines rotate when the magnet rotates? No. 3) Can the seat of induction be unambiguously determined? Yes. 4) Is there a fundamental difference between rotational and translational motional induction? Yes: the “edge effect”, whereby a negative ${rm v}times{rm B}$ field appears whenever a magnetic edge moves perpendicularly to itself. An additional experiment is presented to verify the theory. Finally, 5) Can Relativity Theory be applied? The Special Theory, no; the General one, yes.