- #36
Abid Mir
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M
magnetic force to the left?Philip Wood said:Good. And it's good that, according to BvU, Griffiths also attributes the work done to the power supply.
I don't quite agree with you here. It's not the magnetic field varying with time that induces the back-emf, or, equivalently that causes the 'backward' forces along the wire on the charge carriers. Rather, it's that the wire, and therefore its charge carriers, are moving through a magnetic field, and therefore experiencing a Magnetic Lorentz force, [itex]q \mathbf{v} \times \mathbf{B}[/itex]. This can, if one wishes, be regarded as electromagnetic induction by means of flux cutting, but there's no need to use the terminology of e-m induction: the argument can all be carried through in terms of forces and work, as I did in post 12 and the handwritten continuation.
Note that all this is about forces due to the magnetic field. There is also an electric field, which exerts a force to the right on the charge carriers, opposing the magnetic force to the left, and which is set up by the power supply. This ultimately does the work. [Note that the force between electrons and ions is yet another force due to an electric field.]