(a) Sketch of the experimental setup; a circular U -shaped conductor (orange, with R e = 65 mm ) moves with rotation frequency ν around the z axis (arrows indicate the positive rotation direction). Two coils (in red), whose axes are radially aligned, are used to measure the magnetic coupling between them. (b) Numerical calculations for an oscillating magnetic dipole [in white, for ω 0 / ( 2 π ) = 9 Hz ]. Colors correspond to the real part of the normalized radial field, B ρ / B 0 [where B 0 ≡ μ 0 m / ( 2 π z 0 3 ) with z 0 = 5 mm] for different rotation frequencies of the conductor, ν = − 30 , 0, 11.7, and 36.7 Hz (from left to right). Plots show the magnetic field distribution evaluated at the plane of the dipole. White dots indicate positions where measurements were taken. (c) Out-of-phase component of the voltage measured in the receiving coil (symbols) as a function of the velocity of the conductor [for a signal frequency of ω 0 / ( 2 π ) = 9 Hz ]. Measurements were taken at three different distances from the source coil, r 1 = 11.4 mm (pink), r 2 = 13.1 mm (yellow), and r 3 = 15.5 mm (purple), see inset. For each distance, measurements are normalized to the voltage induced at the receiving coil in free space, | V 0 | . Solid lines are the corresponding numerical calculations considering point dipoles. Shadow areas are defined by considering uncertainties in the experimental parameters used for the numerical calculations [18]. Dashed vertical lines indicate the frequencies of the numerical calculations in (b). Error bars ( 1 σ ) are shown for the three cases; most of them are symbol size or smaller.
PickledPokute on November 22nd, 2018 at 12:20 UTC »
Does this have application in electric motors as a way to eliminate back EMF?
0li on November 22nd, 2018 at 11:01 UTC »
The title implies that they have somehow shown that Maxwell's equations (the basis of all "normal" or classical electrodynamics) are somewhat wrong or incomplete. Two things I have to note, because it's just attention grabbing and I would argue it's somewhat wrong as well:
They used a new metamaterial. I'm pretty sure there is a way (maybe not a pretty one) to just use Maxwell's equations with new material parameters to describe the problem. Which means the crux is more on how to use Maxwell's equations and not with the equations themselves. There are much simpler problem (non-linear materials for example) where solving Maxwell's equations becomes fairly difficult even numerically. But the equations are still almost perfectly accurate as far as we know in those cases. We know that Maxwell's equations are not 100% correct in some cases. They are macroscopic descriptions of electrodynamics. That's why there is quantum electrodynamics (QED) when things get very small.Robotommy01 on November 22nd, 2018 at 10:34 UTC »
Okay cool, I'm an electrical engineering PhD student, and from what I understand in this article they basically spun a conducting cylinder that held Eddy currents(and magnetic fields) produced by one coil, and the coil that received the magnetic fields was a bit further down the circumference of the cylinder, able to receive but not transmit magnetic signals.
It's basically like the motion of the disk creates a sort of magnetic transport where the receiver coil is "downstream" of the other and able to react to the source coil's magnetic field, but the source coil barely feels any magnetic response from the receiver coil. This doesn't break the laws of physics because the conducting spinning disk still reacts to the magnetic fields produced by both coils, it's just that the fields produced by the second coil dissipate through resistive losses before the disk spins the fields back to coil 1.
Like coil 1 is at 0 degrees, coil 2 is at 15 degrees, then there's nothing from 15 to 360 degrees. The disk has to spin 345 degrees to return back to coil 1 after coil 2 and only 15 degrees from 1 to 2. In the 345 degree span the magnetic fields produced by coil 2 have time to dissipate before meeting coil 1.
I hope this explanation helped someone understand this better, and why it's not crazy physics breaking stuff, just something people really haven't thought of doing before!