This isn't quite homework help, although it might seem a little like it.(adsbygoogle = window.adsbygoogle || []).push({});

I was reading my copies of the Feynman's lectures the other day and in volume 1, chapter 2, section 2, "Physics before 1920" he mentioned something which confused me a little: when explaining electric charges and introducing the electric field he sets up a mind experiment in which you shake a charged comb and a little piece of paper, some distance away, moves accordingly, but with a certain delay; then he explains that we then notice something even more interesting, that as we shake the comb we see that the effect of it's charge on the piece of paper falls off more slowly than the inverse of the square of the distance, that is, that vibrating electric charges produce a field which is more far-reaching than the force associated with simple electrical attraction or repulsion.

He follows this up with a metaphor in which he compares the two charges with pieces of cork on a pool (the water being the electric field): we can move one piece of cork by means of moving the other one towards it, thus causing a perturbation in the water which will move the second piece of cork away, even though the effect will be smaller the more distance between the pieces of cork there is; he then adds that by jiggling one piece of cork we can obtain waves whose influence extends very much farther out than the effect of a single movement.

Is he trying to say that only vibrating electric charges produce an electric field? or that the electric field's effect falls of more slowly than the inverse of the square of the distance? I really don't know a whole lot about EM but from what I recall from Resnick's "Physics", charged particles emit a field whether or not they're vibrating, and it's effect also falls off inversely as the square of the distance. I got a little confused and was wondering if someone could clarify what the lectures meant or something.

Sorry for my poor composition skills, by the way.

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# Questions regarding something in Feynman's lectures.

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