How Does Potential Difference Relate to Faraday's Law?

AI Thread Summary
The potential difference between two points is defined as the negative integral of the electric field along a path. In Faraday's law, the closed loop integral of the electric field is equal to the induced electromotive force (EMF), raising questions about why it is not treated as a negative potential difference. The voltage from an induced EMF is calculated differently than from an electrostatic source, leading to the conclusion that induced electric fields do not correspond to a potential function. In a conductor, the total electric field is zero, indicating a relationship between electrostatic and induced fields. Ultimately, the voltage from an inductor reflects this unique behavior of induced EMF.
Nikhil Rajagopalan
Messages
72
Reaction score
5
The potential difference between two points is given ans the negative of integral of E(vector) <dot product> dl(vector) from initial to final points.
Therefore, integral integral of E(vector) <dot product> dl(vector) from initial to final point should give the negative of potential difference between them.
In Faraday's law, closed loop integral of E(vector) <dot product> dl(vector) is given as ε- induced. Why is it not the negative of ε-induced. Should ε-induced not be treated like potential difference?
 
Physics news on Phys.org
The voltage from an EMF with ## V=+\int E_{induced} \cdot ds ## gets computed in just the opposite way of how the voltage from an electrostatic source gets computed as ## V=-\int E_{electrostatic} \cdot ds ##. It should be noted, the induced ## E ## does not give rise to a potential and, in general, ## \nabla \times E_{induced} \neq 0 ##, so that we cannot write ## E_{induced}=-\nabla \Phi ##. The ## V ## from a Faraday EMF is a voltage, at least when it is observed in an inductor, but it is not a potential type function. ## \\ ## In a conductor, since ## E_{total}=0=E_{induced}+E_{electrostatic} ##, we have ## E_{electrostatic}=-E_{induced} ##. The argument can be made that this is why the voltage from an inductor is in fact ## V=\mathcal{E}=+\int E_{induced} \cdot ds ##.
 
Last edited:
Thread 'Motional EMF in Faraday disc, co-rotating magnet axial mean flux'
So here is the motional EMF formula. Now I understand the standard Faraday paradox that an axis symmetric field source (like a speaker motor ring magnet) has a magnetic field that is frame invariant under rotation around axis of symmetry. The field is static whether you rotate the magnet or not. So far so good. What puzzles me is this , there is a term average magnetic flux or "azimuthal mean" , this term describes the average magnetic field through the area swept by the rotating Faraday...
Back
Top