Electromagnetic Induction and Motor Action across Field-Free Regions
Francisco J. M?ller
It is well known that if a wire of length L moves with a velocity v perpendicularly to a magnetic field B, a voltage is induced along the wire equal to BvL. Reciprocally, if a current I is passed through the wire, a motor force F = BIL tends to move the wire in a perpendicular direction. What is less well known is the case in which the wire is shielded from the magnetic field, for example, inserting it in a coaxial iron cylinder. Inside the shield B = 0. Yet, experiments to be described in this paper show that the same voltage BvL appears on the wire, in spite of the zero B where the wire is located. Likewise, upon passing a current through the shielded wire a motor force is still produced, but this time not on the wire, but on the shielding cylinder. On both instances, the induction and the motor force, are occuring across a field free region. The theoretical perplexities entailed by this ?non-local' phenomena, acting at a distance, are discussed.
