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Q & A: electromagnetic induction and current

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Most recent answer: 01/06/2016
Q:
My understanding of how electromagnetic induction works is that a magnet moves over some form of conductive surface, in this case a copper wire, electrons within that wire are then pushed as the magnet is moved down the wire. Now, electrons that were once present at the end of the wire are either not there, or a portion is no longer present, correct? If so then where do the electrons that come to replenish those now missing electrons come from? I thought it possible the electrons could be either free floating electrons that are naturally attracted to the atoms now lacking electrons, or atoms in the air that happened to have extra electrons transferred the electrons to the atoms of the copper wire. If again this is true then within a vacuum where there is a distinct lack of atoms would electromagnetic induction still work, IF no 'new' electrons were being transmitted through the materials used to create whatever device created the electromagnetic induction?
- Nathan
Washington State, U.S.A.
A:

The changing magnetic field does create an electromotive force, a push on any charged particles. That field is preent whether or not there happen to be any charged particles around for it to act on. 

Now if there's a copper wire with two ends around, the conduction electrons will get pushed by that field. Under ordinary circumstances essentially no replacement charges flow in from the air. That will quickly leave the ends of the wire with net charge, just as you say. The field from that net charge counteracts the field from the moving magnet, so the current quickly stops flowing. 

If, on the other hand, the wire is an endless loop, then the current can keep flowing around the loop until the push from the moving magnet stops.

Mike W.

 


(published on 01/06/2016)

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