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Nov28-12, 04:14 AM
Drakkith's Avatar
P: 11,871

An induced electromotive force (emf) always gives rise to a current whose magnetic field opposes the original change in magnetic flux.

As it says here, the EMF causes a current whose magnetic field opposes your original circuit and you have to do work against that magnetic field. But even more basic is the fact that you have to accelerate electrons in the conductor, which requires that you perform work on them, which requires energy to do so, always. The EM field is simply the means by which you accelerate them.