When one has a loop of wire in a changing magnetic field (or a rotating wire loop in a constant magnetic field), Faraday's law says that an EMF -- i.e. a potential difference -- is created. But what does it mean for a loop of wire to have a potential difference? A loop of ideal wire should be an equipotential so unless we have to throw out the notion of ideal wire in this case, I don't see how a potential difference could but created in a single length of wire.
Note that I do understand that a current is created. And I can do the calculations in Faraday's law. I'm just looking for an explanation for what a potential difference in a single loop of wire is supposed to mean.
Answer
This scenario is why EMF and potential difference are not the same.
Electrostatic potential is only defined in situations where there is no magnetic induction. In such cases, then a potential field can be uniquely defined, and we can talk about potential difference, etc.
But when there is a varying magnetic field, and thus an induced current (or more strictly curl of the electric field is non-zero, the electrostatic potential is not a defined quantity, and we can only talk about an EMF generated in the loop.
So it's totally expected that with a loop in a varying magnetic field, you can't define a unique potential at each point on the wire.
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