When I wrote that I was pondering that an infalling particle (ie a specifically undergoing acceleration in a gravity field) will not experience any force on it. Do electrons undergoing gravitational acceleration emit EMR? BHs emit copious amounts of radiation but is that due to particles being superheated as they rub against each other, or is a lot of the emission due to particles (incl electrons) being rapidly accelerated? There are extremely powerful mag fields associated with BHs, so I'm guessing it is due to accelerated charged particles, while the superheated gas aka plasma is responsible for the gamma radiation.
We need to refer to the "paradox of a charge in a gravitational field":
https://en.m.wikipedia.org/wiki/Par...l_field#Resolution_of_the_paradox_by_Rohrlich
The paradox was resolved by Fritz Rohrlich in 1965 by taking appropriate care in distinguishing frames of reference.
He showed that a charged particle and a neutral particle fall equally fast in a gravitational field.
Rohrlich emphasises that the charged particle remains at rest in its free-fall frame, just as a neutral particle would.
And that the charged particle does not radiate in its rest frame, but it does so in the frame of a free-falling observer.
Confused? Then read the full details of the resolution from Wiki and be even more confused! 😵
Just thinking (dangerous) about this further.
Electron drift must surely imply electrons moving a short way, stopping, and then another electron moving and so forth - all repeated in cast numbers in a typical situation. Taken together, you have current flow. If that is the case, each electron must be accelerating, moving, then stopping as it is captured by an atom. So is particle acceleration is responsible for generating the EM field that surrounds a conductor?
Electron drift must surely imply electrons moving a short way, stopping, and then another electron moving and so forth - all repeated in cast numbers in a typical situation. Taken together, you have current flow. If that is the case, each electron must be accelerating, moving, then stopping as it is captured by an atom. So is particle acceleration is responsible for generating the EM field that surrounds a conductor?
I took a quick look. I get that. If you have two co-moving particles, they cannot see any accelerative motion between each other so no EM fields detectable in each other.
If the co-moving particles are accelerating wrt to an independent observer, the independent observer would then detect EM radiation. Relativity again - bit like the glass of water scenario moving at c we discussed a few pages back.
That is one of a set of well defined questions I call "does my bum look big in this" that have no possible correct answer - except to run away....
To all - All free electrons move simultaneously all along the audio conductor in the same direction, then all reverse direction according to the instantaneous audio frequency. It’s an AC circuit. The magnitude of the current is mostly determined by the x section of the conductor, as there are more free electrons moving in larger x sections. Current is a scalar quantity and has no direction, it’s a calculated number. Also, one wonders if F = ma can be applied to the motion of free electrons in the presence of an electromotive force. 🤔
As outlined earlier in the thread, magnetism is entirely a relativistic effect.
Cue impenetrable discussions regarding Lorentz contractions, charge densities and frames of reference! 😱
This link includes an explanatory video: https://www.stem.org.uk/resources/e... moving – relative to something moving slower.
Another eeek moment - power lies outside the conductor. I am also pretty sure about 93% that the EM wave travels through the dielectric material. The plot thickens.
Last edited:
Yeah. The power is carried in E X H. Both are perpendicular to the wire.
So there is a huge legal loophole in cases of power theft from high tension lines! The lawyers can say that the power company should have done a better job of locking it up and that they should have expected this.
So there is a huge legal loophole in cases of power theft from high tension lines! The lawyers can say that the power company should have done a better job of locking it up and that they should have expected this.
Getting back to gravity, if you held a powered AC cable vertically would the drift velocity of the electrons be higher when they traveled toward the floor?
Last edited:
It also works on a bare conductor in a vacuum, aka antenna.
Time would pass more slowly at the cable end closest to the ground so I would assume so. But surely this would be swamped by many orders of magnitude by the electric field/quantum forces at play?
I would agree that gravity will have a vanishingly small influence, if any, on the drift velocity of electrons in a cable - whichever way you care to orientate it.
I'll stick to what I know and leave aside conjecture:
Electromagnetism is often stated to be 10^36 times or 10,000,000,000,000,000,000,000,000,000,000,000,000 times stronger than gravity.
(However, the exact figure depends on which pair of charged particles you choose in order to make the comparison.)
Free electrons in a conductor do accelerate under the influence of the electric force.
However, just like masses falling through the air, the electrons encounter resistance to their motion.
As the electrons speed up, this opposing resistance builds up until it eventually balances out the electric force.
At that point, the acceleration become zero and the electron reaches a terminal velocity.