Does action at distance in electromagnetism violate energyconservation

Click For Summary

Discussion Overview

The discussion revolves around the concept of action at a distance in electromagnetism and whether it violates the principle of energy conservation. Participants explore scenarios involving two charges, their interactions, and the implications of these interactions on energy conservation, particularly in the context of classical electromagnetic theory.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants propose a scenario where charge A is brought closer to charge B, and the work done is zero due to conservative forces, questioning if energy conservation is violated when charge B oscillates without an immediate force acting on it.
  • Others argue that energy conservation does not need to apply instantaneously across a distance, suggesting that energy can still be accounted for over time.
  • Some participants assert that the work done is nonzero due to radiation produced during the interaction, which complicates the energy conservation argument.
  • It is noted that the oscillation energy of charge B depends on its magnitude, implying that larger charges lead to greater oscillation amplitudes without affecting the radiation energy at charge A.
  • A participant references a paper discussing the instantaneous propagation of the Coulomb force, suggesting that this assumption may resolve the paradox, while others express skepticism about the validity of such instantaneous interactions.
  • Some participants highlight the importance of self-force on accelerating particles and challenge claims regarding energy transfer and radiation, invoking Poynting’s theorem as a counterpoint.
  • There are differing views on whether classical energy conservation holds in this context, with some expressing doubt about the authors' solutions in referenced papers.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether energy conservation is violated in the discussed scenarios. Multiple competing views remain, with some asserting that energy conservation holds while others argue it does not in the context of the presented paradox.

Contextual Notes

Limitations include unresolved assumptions about the nature of forces and interactions, the dependence on definitions of energy conservation, and the implications of classical versus quantum mechanical explanations.

hemalpansuriya
Messages
22
Reaction score
7
Consider two charges A and B separated at distance D. charge B is attached on spring and can move towards and away from charge A. Now charge A is brought closer to charge B and then it is taken back to its original position. Work done in this process is zero because of conservative forces. If this action is done in time interval less than D/c, then charge B does not feel any force or reaction during this time. Now as this reaction force reaches to charge B, it will oscillate. In this process work done on charge A is zero but charge B is having energy due to oscillation. Is energy conservation violated in this retarded action ?
 
  • Like
Likes   Reactions: meopemuk
Physics news on Phys.org
hemalpansuriya said:
Consider two charges A and B separated at distance D. charge B is attached on spring and can move towards and away from charge A. Now charge A is brought closer to charge B and then it is taken back to its original position. Work done in this process is zero because of conservative forces. If this action is done in time interval less than D/c, then charge B does not feel any force or reaction during this time. Now as this reaction force reaches to charge B, it will oscillate. In this process work done on charge A is zero but charge B is having energy due to oscillation. Is energy conservation violated in this retarded action ?
Of course not. Where is it written that energy conservation must apply instantaneously across a distance? As long as you remember where you put it, it's accounted for!

Heck, my car has been sitting in my garage with the engine off for two hours and it's still giving off heat!
 
  • Like
Likes   Reactions: meopemuk
hemalpansuriya said:
charge A is brought closer to charge B and then it is taken back to its original position. Work done in this process is zero because of conservative forces.
Work done in the process is nonzero because of the radiation produced.
 
  • Like
Likes   Reactions: vanhees71 and Delta2
Dale said:
Work done in the process is nonzero because of the radiation produced.
Oscillation energy produced at charge B is also depends on magnitude of charge B. Because more charge, more force and hence more oscillating amplitude of charge B. We can take as much large magnitude of charge B as we want. This does not affect radiation energy at charge A, but it will increase energy of oscillation of charge B. So, radiation energy can not account for whatever energy is produced at the charge B.
 
  • Like
Likes   Reactions: meopemuk
Hi hemalpansuriya,

I like your paradox. A similar setup was discussed in

A. Kislev, L. Vaidman, "Relativistic causality and conservation of energy in classical electromagnetic theory", Am. J. Phys. 70 (2002), 1216; arXiv:physics/0201042v1

But I don't think the authors did a good job at providing a solution.
Eugene.
 
meopemuk said:
Hi hemalpansuriya,

I like your paradox. A similar setup was discussed in

A. Kislev, L. Vaidman, "Relativistic causality and conservation of energy in classical electromagnetic theory", Am. J. Phys. 70 (2002), 1216; arXiv:physics/0201042v1

But I don't think the authors did a good job at providing a solution.
Eugene.
Yes, I have also gone through it. But I am not convinced with author's solution. I believe that for this problem classically energy can not be conserved. I don't have any further quantum mechanical explanation.
 
  • Like
  • Sad
Likes   Reactions: weirdoguy and meopemuk
Here is another relevant paper:

W. Engelhardt, "Relativity of Time and Instantaneous Interaction of Charged Particles", Am. J. Mod. Phys. 4 (2015), 15.

It discusses exactly the same setup with two charges as proposed by you. The author seeks the resolution of this paradox in assuming the instantaneous propagation of the Coulomb force. There is experimental evidence that this assumption may have some validity:

R. de Sangro, G. Finocchiaro, P. Patteri, M. Piccolo, G. Pizzella, "Measuring propagation speed of Coulomb fields", Eur. Phys. J. C, 75 (2015), 137. arXiv:gr-qc/1211.2913v2.

Eugene.
 
meopemuk said:
Here is another relevant paper:

W. Engelhardt, "Relativity of Time and Instantaneous Interaction of Charged Particles", Am. J. Mod. Phys. 4 (2015), 15.

It discusses exactly the same setup with two charges as proposed by you. The author seeks the resolution of this paradox in assuming the instantaneous propagation of the Coulomb force. There is experimental evidence that this assumption may have some validity:

R. de Sangro, G. Finocchiaro, P. Patteri, M. Piccolo, G. Pizzella, "Measuring propagation speed of Coulomb fields", Eur. Phys. J. C, 75 (2015), 137. arXiv:gr-qc/1211.2913v2.

Eugene.
According to this author, interactions are instantaneous, which we know it can not be true. As light also have finite speed, Coulomb interactions can not be instantaneous. The only way is, energy is not conserved.
 
hemalpansuriya said:
We can take as much large magnitude of charge B as we want. This does not affect radiation energy at charge A, but it will increase energy of oscillation of charge B.
Don't forget the self force on an accelerating classical point particle. That is the problem with all such analyses.

hemalpansuriya said:
So, radiation energy can not account for whatever energy is produced at the charge B
Please show your work.

Poynting’s theorem guarantees that this claim is false. The self force is essentially a free variable which can always be set to satisfy Poynting’s theorem.
 
Last edited:
  • #10
Dale said:
Please show your work.
Any arbitrary large value of charge B does not increase the energy radiated by charge A. But , having larger value of charge B will produce large amount of oscillating energy. So, we can not have equal amount of energy transfer here. Moreover, radiated energy from charge A does not even reach to charge B, because charge B is placed in line with acceleration vector of charge A. Energy radiated by any charge in line of its acceleration vector is simply zero.
 
  • Skeptical
Likes   Reactions: weirdoguy
  • #11
Handwaving is not showing your work.

Your handwaving neglects both the self force at B and also Poynting’s theorem. Show your work including both. You are making an exceptionally strong claim with an exceptionally weak justification.

Also, since the problems with classical point particles are well known it would be more convincing to use something more realistic.
 
  • Like
Likes   Reactions: weirdoguy
  • #12
hemalpansuriya said:
Yes, I have also gone through it. But I am not convinced with author's solution. I believe that for this problem classically energy can not be conserved. I don't have any further quantum mechanical explanation.
I've not followed the argument in the paper yet, but in classical electromagnetic theory energy is always strictly conserved. You only have to carefully take into account the total energy-momentum-stress tensor.
 
  • Like
Likes   Reactions: Dale
  • #13
This thread is closed for now. Please PM me with your work to reopen it.
 

Similar threads

  • · Replies 15 ·
Replies
15
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 61 ·
3
Replies
61
Views
6K
  • · Replies 7 ·
Replies
7
Views
2K
Replies
29
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 11 ·
Replies
11
Views
5K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K