Timeline for Relativistic explanation of attraction between two parallel currents
Current License: CC BY-SA 3.0
11 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jun 1, 2023 at 15:49 | comment | added | Frank Breitling | This answer and many comments are confusion and wrong. A correct answer argues with the $B$ field of the protons and the Lorentz force like here or here. | |
| Jun 23, 2022 at 12:12 | comment | added | J Thomas | "The coulomb forces from the protons in WIRE 1 cancel each other out, because the electrons in WIRE 1 are between the protons of WIRE 1, so their net force is zero." No, they don't cancel. In the electron's frame those protons are moving at speed beta. So their force is proportional to 1/(1-beta)^2 in one case, and 1/(1+beta)^2 in the other. | |
| Mar 14, 2017 at 2:27 | comment | added | akhmed | The key element is the symmetry: @Bass answered it himself correctly in the 2nd comment. From the point of view of each electron, protons do have higher density in WIRE1 and WIRE1 becomes positively charged. However, this has no effect on the electron -- since WIRE1 protons cancel each other out -- they are all around the electron. | |
| Oct 22, 2015 at 15:05 | comment | added | Bass | Anyway, I understand the problem now, thanks for you help :) | |
| Oct 22, 2015 at 15:05 | vote | accept | Bass | ||
| Oct 22, 2015 at 15:05 | comment | added | Bass | "The coulomb forces from the protons in WIRE 1 cancel each other out, because the electrons in WIRE 1 are between the protons of WIRE 1, so their net force is zero." I mean that as long as everything is distributed homogeneously in the wire, there are no forces on the electrons from the wire they're in. This is clear from simple symmetry arguments. | |
| Oct 22, 2015 at 14:56 | comment | added | SchrodingersCat | (Contd.) By relativity, electrons cant say from their own reference frame that a property due to them has increased without themselves increasing. Take an analogy. A train is going by and I am standing still near the rail tracks. A friend is on the train. From my ref frame, I am still and I have no K.E. But from my friend's ref frame, the train is still and I have K.E. But he will never be able to measure my velocity for which I have K.E. nor will I ever claim that yes I have K.E., the train is still. | |
| Oct 22, 2015 at 14:50 | comment | added | SchrodingersCat | How do you type so fast? I barely finished writing the same thing. Anyways your reasoning is partially right. However I couldn't get what you meant by "The coulomb forces from the protons in WIRE 1 cancel each other out, because the electrons in WIRE 1 are between the protons of WIRE 1, so their net force is zero." One point I would like to add is that if the electrons in WIRE 1 see more protons in WIRE 1,then it will seem the wire has length contracted implying higher positive charge density and similarly higher negative charge density too. Which is a contradiction. | |
| Oct 22, 2015 at 14:42 | comment | added | Bass | I have a proposal for a new third point in your explanation: 3. The electrons in WIRE 1 see more protons in both wires. The coulomb forces from the protons in WIRE 1 cancel each other out, because the electrons in WIRE 1 are between the protons of WIRE 1, so their net force is zero. The coulomb force of the protons in WIRE 2 attract them. The thing I got wrong: The protons in WIRE 1 must be considered in their reference frame. There, the protons are at rest and the electrons are moving, so the protons see more electrons, so they are attracted too. | |
| Oct 22, 2015 at 14:38 | comment | added | Bass | Well I think I'm starting to understand it. However, I'm not sure if I can follow your third point. Why don't the electrons in WIRE 1 see more protons in WIRE 1? In their reference frame, the protons in WIRE 1 are moving exactly the same way as they are in WIRE 2. | |
| Oct 22, 2015 at 13:37 | history | answered | SchrodingersCat | CC BY-SA 3.0 |