Dale -
Thanks - that's very helpful. You write:
" The Noether current and the Noether charge are related through a continuity equation which essentially defines a local conservation law. "
What is the continuity equation?
Where does the J I see so often come in? Aclaret's post as is is a...
As I understand it for every symmetry there is associated a conserved quantity - so for time symmetry there is energy conservation. I understand as well that charge conservation is associated with a 'mathematical' local symmetry - something turning in a mathematical space at a point so to...
I am trying to understand why an accelerating charge emits radiation/electromagnetic waves but a uniformly moving one does not. I saw one video on Youtube where it seemed that it was explained by the fact that with a uniformly moving charge the Poynting vector was pointing 'in to the volume' -...
Nugatory/Davenn
Thanks for the clarification. Those are the kinds of answers I was expecting to get and most always have gotten on PF.
The articles I read prior to posting - many of them - did not make the critical distinction between accelerating and non-accelerating charges - you can see...
Google:
+++++++++++++++++++
https://www.google.com/search?q=moving+charges+electromagnetism&oq=moving+charges+electromagnetism&aqs=chrome..69i57.10416j0j7&sourceid=chrome&ie=UTF-8
"Electromagnetic radiation, is a form of energy emitted bymoving charged particles. "
"When a charged...
Let us say I have a moving charge. At each point x,y,z in it's path from understanding there is a transverse electromagnetic wave being radiated (could also be viewed as a photon). The electric field at any point x1,y1,z1 in the path is disturbed. The moving charge does the same thing all...
Thanks for the quick and definitive response. This point was not made clear in a lot of material I saw - it always had reversal of direction - so negative and positive charges swapping repeatedly. That being said what difference does that particular scenario make as to the simply...
I would very much appreciate a clarification on what is meant by a changing electric field in the context of statements such as 'a changing electric field creates a changing magnetic field'. My question is does the electric field actually need to reverse as a lot of examples show where two...
sophiecentaur:
Thanks for quick reply. However I do not know what E and H are that you refer to?
CWatters: Thanks for the link but I see nothing in there about potential and kinetic energy of an electromagnetic wave. I saw a video about a string wave on Youtube and with the string I understood...
Do electromagnetic waves have potential and kinetic energy like springs, strings, etc. If so how are they calculated, inter-related? What is the total energy? Are the energies fluctuating over time?
I am a physics hobbyist so generally the first answers should come with the least mathematics...
Thanks for the distinction between gauge symmetry and gauge invariance. I think however based on the amount that I see gauge symmetry used it will be a long battle to knock it out of use. Or is there such a thing as gauge symmetry apart from gauge invariance?
Thanks. So what is the formula for calculating A using the parameters referenced? A picture or illustration would be great so I can see what exactly the variables refer to.
In this article https://terrytao.files.wordpress.com/2008/03/ricci1.pdf the following is written:
"Consider now an angular sector A(x, r, θ, v) inside a small disk B(x, r) of small angular aperture θ (measured in radians) centred around some direction v (a unit vector) emanating from x; this...
I have reviewed the various posts on gauge symmetry in particular this one which is now closed. In this post there is the following link:http://www.vttoth.com/CMS/physics-notes/124-the-principle-of-gauge-invariance.
This is a good read. However, there is some clarification I need.
The...