Timeline for If you run an electric current through a wire loop, do the accelerated charges radiate?
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10 events
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| Aug 21, 2022 at 17:00 | comment | added | J Thomas | You're talking about the average of around a quintillion electrons. A disproportionate part of the distance traveled, is traveled by the ones that are going fast. I may be reading the equation wrong, but it looks to me like the length of the radiation vector is sometimes proportional to beta'/(1-beta)^3, So if one electron was traveling at .999c while a thousand others were at rest, the same acceleration would produce a billion times the radiation you'd get from 1001 electrons all traveling at .001c. But the average velocity would be similar. | |
| Sep 5, 2016 at 21:24 | comment | added | jim | In fact, this has been posed and answered, see physics.stackexchange.com/questions/4199/… | |
| Jul 12, 2016 at 18:53 | comment | added | jim | "a synchrotron, the currents are not constant but instead come as pulses" So, if you have arrange the synchrotron such that there is a uniform density around the loop, no radiation? | |
| Jul 10, 2016 at 18:39 | comment | added | jim | @CarlBrannen For interest, the problem seems to have been first put forward by J.J. Thomson, The Magnetic Properties of Systems of Corpuscles describing Circular Orbits, Phil. Mag. 36, 673 (1903) | |
| Aug 12, 2011 at 17:30 | comment | added | Carl Brannen | I'm feeling really doubtful of my arguments here and would appreciate a critique so that I can go ahead and delete the answer. | |
| Aug 11, 2011 at 16:33 | comment | added | Carl Brannen | @Ben; I keep going back and forth on this. First, I never said drift velocity is universal; I did the calculation with copper because this is common for circuits. Second, if you make v large enough you end up with synchrotron radiation. But I agree that if the - charges of the electrons are exactly cancelled by the + charges of the metal then there is no radiation of this sort. But an exact cancellation is not compatible with a change in the current; for the usual metals, one must have voltage to have current and this implies that the + and - charges did not cancel exactly. | |
| Aug 11, 2011 at 14:50 | comment | added | user4552 | There are a couple of problems with this answer. One is that the drift velocity is not universal, as you seem to be claiming; it depends on the material. The other is that it is possible to make the acceleration as large as desired simply by making v large and/or making R small. Even with large a, there is no radiation, but your answer makes it sound as though there is. | |
| Aug 10, 2011 at 22:30 | comment | added | Carl Brannen | The answer by user1631 is also correct (I believe), but only applies to constant currents. In a synchrotron, the currents are not constant but instead come as pulses. | |
| Aug 10, 2011 at 22:20 | comment | added | Revo | Yeah that is the intuitive answer I had in mind, electrons in a current loop radiate but the radiation is infinitesimally small because the drift velocity is infinitesimally small. | |
| Aug 10, 2011 at 21:34 | history | answered | Carl Brannen | CC BY-SA 3.0 |