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This question already has an answer here:

Say, there are 2 stationary electrons placed at a distance. The result of observation would be both flying apart with the same speed and the opposite direction, which would obey laws of conservation of momentum and energy (as electric potential energy is converted into kinetic energy). But if considered from the perspective of emitting and receiving photons, how is the process like? Where does the energy come from? Does the mass of either electron change? Or should I not try to understand it from the classic point of view?

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marked as duplicate by ACuriousMind, Kyle Kanos, John Rennie, user10851, user36790 Nov 1 '15 at 3:51

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  • $\begingroup$ the checked answer here might help physics.stackexchange.com/questions/189605/… $\endgroup$ – anna v Oct 31 '15 at 17:12
  • $\begingroup$ Just as a warning, the picture that suggests the literal mediation of forces trough bosons is a result of a mathematical procedure called "perturbation theory". One shouldn't take the picture too seriously, as it causes all kind of conceptual problems if one takes it too far. $\endgroup$ – CuriousOne Oct 31 '15 at 21:18
  • $\begingroup$ I was trying to answer when they closed it as duplicate. "from the perspective of emitting and receiving photons, how is the process like". This perspective comes from the Feynman diagrams . The diagrams are an iconal representation of terms in the expansion of the perturbative solution for the specific problem. In your case electron electron scattering (interaction). if you look at the diagram in this link i.stack.imgur.com/aoydt.png you will see the representation of a photon in the exchange. It is not a real photon, but a mathematical stand in. It is called a virtual photon because $\endgroup$ – anna v Nov 1 '15 at 4:00
  • $\begingroup$ It has all the quantum numbers of a photon except its zero mass. Its line represents the photon propagator, en.wikipedia.org/wiki/Propagator under the total integral which calculated will give the first order term in the perturbative expansion of e-e- scattering. There are higher order terms with more virtual particles, but this one is dominant; thus the photon has been considered the main electromagnetic force carrier, introducing some confusion. Note that the propagators become infinite when the four vectors are on mass thus the exchanged energy and momentum cannot be on mass. $\endgroup$ – anna v Nov 1 '15 at 4:19
  • $\begingroup$ The energy of the interaction comes from the potential : the two electrons each at its space point have potential energy , they were somehow brought there by the experimenter. $\endgroup$ – anna v Nov 1 '15 at 4:21
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From the classical view there are electric and magnetic fields throughout space.

And they have their own energy. And the energy in the fields changes as the fields change.

And when there are charges the fields change differently there. They change in a way where energy flows from the fields into the charges where the electric field points the same direction as the current and it flows from the charges to the fields in places where the electric field points the opposite direction as the current.

And that's exactly when the kinetic energy of the charges changes. And the energy from the fields is spread out in space where the fields are and it is the energy in the fields right there where the charge is that is exchanged with the charges right there.

No potential energy involved.

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