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The Faraday paradox is a hard one to get ones head around and I was wondering if there is a similar scenario, involving an E field where there is / or is not an induced emf?
sophiecentaur said:The Faraday 'paradox' is because moving the disc or magnet produces an emf, or not - depending. The Field seems to behave as if it has its own reference frame (I think). So I was looking for an example in which the E field appears to have its own frame, too, I guess, so that there could be the equivalent of emf/ no emf. I am being vague because I really have no idea of a scenario - there is often a sort of E-H symmetry and I thought there may be something here.
sondreL said:finally someone made a thread like this , I've been thinking about it too many times even here on PF a while ago , sophie probably wouldnt't remeber as it was under a different name. Blackadder is great , thanks sophie for the recomendation :)
about the faraday disc itself I think sophie you already know how it works , due to the difference in tangential speed from the inner portion of the disc to the outer one the b field makes a net electron flow from center to outside or vice versa depending on the applied b field polarity , the thing i couldn't get my heada round too is why rotating just the magnet doesn't produce any current while spinning the magnet together wioth the copper disc synchronously, produces the same current as when the magnet is stationary while the disc spins with respect to the magnet, really strange. the only logical thing that comes to mind is that the b field of a permanent magnet is stationary and for an even geometry magnet the same at all places so whether one spins the magnet or keeps it stationary doesn't make a difference in the field lines nor the pole orientation nor the field strength so basically the copper disc sees a stationary field no matter whether the magnet spins or not. could you please explain more about your imagined E field situation with respect to the faraday disc , it would be very interesting to know your thoughts more , thank you :)
This isn't my understanding. The Arago magnetism of rotation requires the presence of a magnetic field in addition to a spinning non-ferrous disc like copper. The basic phenomenon is eddy currents induced by the B field.Blibbler said:The key to understanding the Faraday disc lies in understanding Arago's magnetism of rotation, where a copper disc is rotated and is seen to affect a nearby magnet. This shows that merely spinning a copper disc generates a magnetic field.
The Faraday disc paradox is a thought experiment that explores the relationship between magnetic fields and electric fields. It involves a rotating disc made of a conducting material, with a magnet placed at the center. According to Faraday's law of induction, a changing magnetic field will induce an electric field. However, in this situation, the disc is rotating and the magnetic field is not changing, leading to a paradox.
The resolution to the Faraday disc paradox lies in the fact that the disc is not a perfect conductor. As it rotates, small electric currents are induced in the disc, creating a magnetic field that opposes the original magnetic field. This opposing magnetic field is what allows the disc to continue rotating without violating Faraday's law.
Yes, there is an equivalent situation with E fields known as the Faraday's wheel paradox. In this experiment, a wheel with conducting spokes is rotated between the poles of a magnet. Similar to the Faraday disc paradox, the electric field is not changing, but the wheel continues to rotate due to the induced magnetic field from the electric currents in the spokes.
The Faraday disc paradox highlights the intricate relationship between electricity and magnetism, and how they are intertwined. It also demonstrates the concept of electromagnetic induction, which is the basis for many modern technologies such as generators, motors, and transformers.
The Faraday disc paradox is a consequence of Maxwell's equations, which describe the behavior of electric and magnetic fields. Specifically, it is related to Faraday's law of induction, one of the four Maxwell's equations. This paradox serves as a practical example of the principles outlined in Maxwell's equations.