Timeline for Special relativity and electromagnetism
Current License: CC BY-SA 3.0
7 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Dec 10, 2014 at 21:55 | vote | accept | Phil Frost | ||
| Jul 10, 2014 at 22:46 | comment | added | Alfred Centauri | @PhilFrost, it's an interesting path you're on but keep in mind that, for this problem, we're assuming steady currents. Once you allow for acceleration (time changing current), things get much more complicated. In the steady current case, the mobile electrons are all assumed to be in the same inertial frame of reference. However, this isn't the case when the mobile electrons are accelerating. We must then consider momentarily co-moving reference frames and, perhaps, assign a different one to each electron. | |
| Jul 10, 2014 at 17:34 | comment | added | Phil Frost | I think it takes more than 1 comment's worth of words to phrase my question, so: Special relativity and inductance | |
| Jul 10, 2014 at 17:16 | comment | added | hmakholm left over Monica | @PhilFrost: I think a more complex analysis is necessary to explain Faraday's law -- a naive application seem to lead to an effect of the wrong sign. However, one also has to take into account that changes in the electic field propagate with finite speed, and that the electrostatic repulsion from a moving charge in the direction of its movement is less than that of a stationary charge. (In the transverse direction it is the same). This is not part of Coulomb's law but has to be derived using relativity -- it's the only way for things to fit together in a consistent way mathematically. | |
| Jul 10, 2014 at 17:08 | comment | added | hmakholm left over Monica | @PhilFrost: From the cat's frame, some electrons are removed from the wire during the transition -- because the cat sees electrons begin leaving the front end of the wire before new electrons begin moving into its back end. (Of course it is an impossibly idealized assumption that the current starts instantaneously from the wire's rest frame, but the net outcome is the same for less sharp transitions). | |
| Jul 10, 2014 at 17:03 | comment | added | Phil Frost | Yessss. I'm grasping it now. So I wonder, as you transition from "no current" to "some current", you must either (from a frame where the electrons are stationary) decrease the electron density, or (from a frame where the protons are stationary) manage to get the electrons moving while seemingly countering the effects of length contraction. When I think about this, I wonder if it also explains Faraday's law of induction, in that although the current-carrying wire in the lab frame is neutral, time varying currents can induce voltages. Is that the right track? | |
| Jul 10, 2014 at 16:58 | history | answered | hmakholm left over Monica | CC BY-SA 3.0 |