- #1

Will Learn

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I'm not sure where to put this question, it concerns particles, mass-energy equivalence and various things. Classical electromagnetism seems to be as sensible a place as any.

There is energy stored in an E field.

Energy density (at position r, time t) = [tex] \frac{1}{2} {\epsilon} |E(\vec{r},t)|^2 [/tex]

(Minor note: I can't find any guides on how this forum supports LaTex, I hope the above prints. If there is a guide and anyone can give a link to the guide that would be a help).

So, a charged particle should create a E field throughout all of space. Does that energy density contribute to the mass of the particle? To say this another way, is some of the inertial mass of the particle non-local to the particle?

For example, if you changed the permittivity of space somewhere, which you might do by flooding a region with some dielectectric material, can you affect the resistance that the particle would show to an applied force (i.e. change it's inertial mass) even though you have been changing something that is some distance away from the particle?

Anyway, the basic question is:

**Does the energy stored in the E field contribute to the inertial mass of a charged particle?**Moving the particle clearly forces the E field to change throughout space. So that if the particle is accelerated, then some energy located in space (which would seem to be equivalent to a mass) is also accelerated. That mass/energy in the E field seems to be dragged around with the particle, so you might expect the increased inertia to be noticed or evident at the point of contact by an applied force on the particle.

I don't know. I can't get to any place with Physicists at the moment, so I'd be grateful for any answers from the forum. I've got a copy of Electrodynamics by Griffiths at home and of course, the internet, if anyone wants to suggest a reference.

Thanks for your time.