I would like to know if electricity will follow a path of least resistance on a rotating conductor.

Please reference the drawing below.

This is showing a rotating non-conductive disc with a strip of copper around its perimeter and there are two brushes (blue squares) which the DC electrical current is flowing through. Say that this disc is 4 inches in diameter and the copper strip is moving at a rate of 130 fps.

Would electricity take the path indicated in the drawing since the free electrons would be moving with the atoms in the copper strip in contrast to the other available path, in which the free electrons would have to flow against the oncoming atoms in the copper strip?

Also, as a secondary question concerning this setup, would centrifugal force acting on the copper atoms and on the free electrons have any effect on the flow of electricity?

enter image description here

  • $\begingroup$ While free, what should "drag" the electrons apart from the symmetric electric field? $\endgroup$ – Hagen von Eitzen Apr 14 at 20:40
  • $\begingroup$ @HagenvonEitzen, that is what I am unclear about. I'm not sure if there will be a drag or not. $\endgroup$ – user217618 Apr 14 at 20:52
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    $\begingroup$ FWIW, electricity takes all paths, inversely proportional to their resistance. It's not just one path. If there is a difference in resistance caused by the rotation, it will be very small and we'd still say the electricity takes both paths. $\endgroup$ – immibis Apr 14 at 23:10
  • $\begingroup$ what do you think will happen if you keep the disk stationary and rotate the pair of terminals ? $\endgroup$ – user8718165 Apr 16 at 2:09
  • $\begingroup$ Rotation shouldn't affect the answer ... the electric field propagates through the conductor at practically the speed of light. $\endgroup$ – David White Apr 16 at 2:22

Let's not talk about the direction of conventional current.

The negative terminal has a habit of repelling away electrons due to the electric field there.

You can imagine that just after a while there will be slightly higher electron density at the negative terminal and a slightly lower electron density at the positive terminal due to the combined effect of the electric field at the terminals and rotation. However that isn't something that keeps happening otherwise you'd end up with loads of charges at the terminals. Also charges hate very much being stuffed up together. I think that pile-up process will continue for a period of time (however small that interval may be) until the repulsive forces are strong enough to drive the electrons against the rotation.

Moreover the electrons moving in the same direction might speed up (for a while) but that isn't going to increase the current because the external wires offer finite resistance to the flow of current.

  • $\begingroup$ I agree with your explanation of what will likely occur, yet does this mean that the majority of the electric current flowing between the two terminals will occur over the path where the electrons are moving in the same direction? If so, that would establish a path of least resistance, correct? $\endgroup$ – user217618 Apr 16 at 2:47
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    $\begingroup$ yes most of the current flow will occur the the way where the resistance is low governed by $I\propto \frac1R$. So a greater magnitude of current flow will occur the way where the direction of rotation is the same as the direction of electron flow. $\endgroup$ – user8718165 Apr 16 at 2:57

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