More or less I have come across two concepts to explain non contact forces:

  1. FIELD CONCEPT: modification of space by the source which in turn produces force on the other (That is in my classroom course)

  2. EXCHANGE FORCE : which I recently read in wikipedia ( Infact just before writing this post)

After reading the concepts, it is quite expected that one would try to correlate them as both are true in their explanations (as far as I know, do let me know if it is the other way )

I was thinking that is it so that the source continuously emits the exchange particles (photon for em, gluon for quarks etc. ) to create the field around it which interacts with the other one. I know it would come under the banner "generation of field" but the idea links both of them and as far as is the concern of description of generation of field my book is quite vague in that (high school)- it simply says that "source modifies the space around it"

But certain doubts arise in my mind ;

  1. Don't you find such creation quite weird that source continuously emits the exchange particles

  2. Secondly, continuous emission will create some impact over the source

Then, how are field generated?

  • $\begingroup$ A field does not consist of real particles, but of virtual particles and they are not real. The source doesn't continuously emit them. Perhaps a bad analogy, but it's more like a spark between two charged balls. One ball doesn't continuously emit sparks, it only emits one to hit the other ball once they get close. Again, perhaps a bad analogy but may be helpful sometimes. $\endgroup$ – safesphere Sep 30 '17 at 4:19
  • $\begingroup$ "the source doesn't continuously emit them" then do they "emit" them only on arrival of test particle. Really?, I have read that electric potential doesn't appear of test charge ( potential is measure of electric field) what is the answer? $\endgroup$ – Pranjal Rana Oct 1 '17 at 8:07
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    $\begingroup$ I always recommend this: profmattstrassler.com/articles-and-posts/… $\endgroup$ – Javier Oct 1 '17 at 20:54

Quantum fields interact in a quantum way ("digital" instaed of "analog"). Two charged particles both have quantum fields. These fields are NOT the electromagnetic field. Quantum fields are not real in the sense that they cannot be directly measured or observed. They represent the probability of the interaction. The fields don't constantly "feel" each other, do not constantly attract, repulse or interact in any way. Then at some random point (with the probablity defined by the fields) a momentary interaction happens, after which the fields again do not "feel" each other. This interaction tranfers energy, momentum, and certain quantum numbers (depending on the type of interaction this could be charge, "color", etc.). The values transferred by the interaction (except for the mass) look like they could belong to a particle, but this particle does not actually exist. Therefore, for simplicity, sometimes the interaction is viewed as an exchange of a virtual particle, where "virtual" as opposed to "real" emphasizes that this particle does not exist, but is just a way to combine the transferred values into a single hypothetical object.

Referring to your question, this interaction (or a "virtual particle", if you will) is an electromagnetic interaction and a part of the electromagnetic field. When you have many of such interactions, their quantum ("digital") nature averages out and you see a continuous ("analog") classical electromagnetic field. In the sense described above you can hypothetically say that the electromagnetic field consists of "virtual photons", as long as you remember that they don't actually exist, but are only a convenient way to decsribe how the quantum fields interact.

As you hopefully can see, virtual photons are not emitted constantly, but only "on demand" when the quantum fields of two particles "decide" to interact at a random point, but on average based on the probabilities defined by the intencity of the fields. Once again to emphasize, the quantum fields do not directly represent the electromagnetic field. The electromagnetic field is represented by a statistical sum of a large number of interactions between the quantum fields. And in a simplified way these interactions sometimes can be viewed as exchanges of "virtual particles", as long as we remember that they are not real and therefore do not actually exist. So in this view, one could say that the electromagnetic field consists of virtual photons as hypothetical objects representing quantum interactions between the quantum fields.

In contrast with the electromagnetic field, the electromagnetic wave can be viewed as consisting of real photons, but this is a different topic.

  • $\begingroup$ Wouldn’t it be entertaining to postulate that electric field, magnetic field and EM radiation are made from fundamental particles and by this deduce explanations for electron-proton interactions in atoms, annihilation processes and of the electric and magnetic field components of the photon? $\endgroup$ – HolgerFiedler Oct 5 '17 at 21:08

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