might suggest that the retarded scalar potential for a moving point charge is {also } .. Thus, we have obtained the so-called Liénard-Wiechert retarded potentials. Lecture 27 – Liénard-Wiechert potentials and fields – following derivations in. Lecture When we previously considered solutions to the. The Lienard-Wiechert potentials are classical equations that allow you to compute the fields due to a moving point charge in the Lorenz Gauge Condition.

Author: Jumuro Kilmaran
Country: Zambia
Language: English (Spanish)
Genre: Sex
Published (Last): 27 May 2005
Pages: 291
PDF File Size: 8.82 Mb
ePub File Size: 4.69 Mb
ISBN: 259-2-90328-312-8
Downloads: 68420
Price: Free* [*Free Regsitration Required]
Uploader: Gardagar

I have corrected the section reference. Aspden has worked on various aspects of aether theories, and Whitney is also against notions of Einsteinian relativity, which led to their work being largely disregarded by the physics community at large. This trick allows Maxwell’s equations to become linear in matter. The rest, you seem to just be wicehert the results, but not really address my argument. We can calculate the electric and magnetic fields directly from the potentials using the definitions:.

Electrodynamics/Lienard-Wiechert Potentials – Wikibooks, open books for an open world

Linearity of Maxwell’s equations in wiecgert allows one to add both systems, so that the charges disappear: I said ” It seems to me that it is this extra counting which makes the potential to be larger than expected”, so I agree with what you say in the first paragraph. Only this second term describes information transfer about the behavior of the charge, which transfer occurs radiates from the charge at the speed of light.

By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy wiecbert and cookie policyand that your continued use of the website is subject to these policies. However, under certain conditions, there always exists a retarded time. Thus, the charged particle is “smeared” out! The first of these is the static electric or magnetic field term that depends poential on the distance to the moving charge, and does not depend on the retarded time at all, if the velocity of the source is constant.

So why is my argument wrong? So think the way to think of it, is that the terms in the wiecherf for the potential act as an “enhancement factor” to the charge because of the integration over it’s history where the same spatial element of the charge may contribute over a period of time to the potential felt at any given moment to the observer.


Lamb’s correction of levels of H atom. From Wikipedia, the free encyclopedia. Note the appearance of the “stretching” or “over-counting” factor. Sign up using Email and Password.

However, it is clear that if the charge cloud was small enough, or if we were far enough, the potential would be just the potential for a point charge of charge equal to the total charge of the cloud, as no charge is “overcounted” something which is also due to the cloud’s speed being less than c. Post as a guest Name.

Electrodynamics/Lienard-Wiechert Potentials

When you say “it is clear that if the charge cloud was small enough, or if we were far enough, the potential would be just the potential for a point charge of charge equal to the total charge of the cloud” you’ve also implicitly made the assumption that the charge is moving slowly enough that it’s distribution may be integrated over at a single time co-ordinate.

Advanced fields are absorbed by the charges and retarded fields are emitted. Hmmm, I think I may have misinterpreted your question somewhat. I like it, except this bit:. The argument proceeds in two steps: It is important to take into account the zero point field discovered by Planck M.

Retrieved from ” https: A particle on Earth ‘sees’ a charged particle accelerate on the Moon as this acceleration happened 1. This is not an effect of length contraction; this is rather more similar to the Doppler shift.

Email Required, but never shown. The direction of the field associated with potemtial radiative term is toward the fully time-retarded position of the charge i. However, we will observe the particle to have length b, because the light that is simultaneously reaching our eyes from the front and back of the box originated from different times. Jackson refutes Chubykalo’s argument by claiming that Lienard-Wiechert potentials are indeed a solution of Maxwell’s equations, but Chubykalo did not state the issue as precisely as Whitney, which is related to boundary conditions rather than lienarf to the differential equations.

Electromagnetic radiation in the form of waves can be obtained from these potentials. To evaluate this integral, therefore, we need the identity.

From Wikibooks, open books for an open world. These are the Lienard-Wiechert Potentials for a moving charge. To see why, consider the following situation with discrete charges: The second term, however, which contains information about the acceleration and other unique behavior of the charge that cannot be removed by changing the Lorentz frame inertial reference frame of the observeris fully dependent for direction on the time-retarded position of the source.


Retrieved from ” https: Thanks again for the catch. Wikipedia articles needing clarification from November Jackson also points out that other gauges in classical electrodynamics lead to instantaneous dynamics, but is not needed in the Lorenz gauge.

Liénard–Wiechert potential – Wikipedia

To compute energy, it is necessary to use the absolute fields which includes the zero point field; otherwise, an error appears, for instance in photon counting. As to why this we may apply this reasoning to the case of discrete point charges, Feynman provides: According to her, this is due to a Jacobian factor missed, as many physicists do not apply a rigorous treatment of distribution theory and work with the Dirac delta function.

It seems to me that it is this extra counting which makes the potential to be larger than expected, and I am uncomfortable with it. Thus, static fields the first term point exactly at the ptential instantaneous non-retarded position of the charged object if its velocity has not changed over the retarded time delay.

Liénard–Wiechert potential

A charge moving with a constant velocity must appear to a distant observer in exactly the same way as a static charge appears to a moving observer, and in the latter case, the direction of the static field must change instantaneously, with no time-delay. Ah, Jackson sections The correction factors are for the components of velocity pointing to the point we are measuring the potentials at. My thesis briefly discusses aspects of Whitney’s argument and cites many relevant references for further study.

Btw, a minor thing, but I think that your 4-current should have an extra factor of c Jackson agrees with me. Electromagnetic tensor stress—energy tensor.

I don’t wiecheft the increase in potential due to the moving charge leading to an “overcounting” IS in disagreement with Feynman’s result. Feynman’s proof utilizes a geometrical and fundamental integration argument.

This second term is connected with electromagnetic radiation.