Talk:Poynting's theorem

message: Isn't the right side the negative of the total power done by the electric field?  Not work...  --Bmk 15:01, 25 July 2006 (UTC)
replies: text: Yes. Fixed now. JRSpriggs 05:30, 26 July 2006 (UTC)
thread_title:  Old Comments 

message: Hello, this statement is totally wrong : "Poynting's theorem takes into account the case when the electric and magnetic fields are coupled – static or stationary electric and magnetic fields are not coupled. In other words, Poynting theorem is valid only in electrodynamics."
take a look at the feynman course. Wwe can define a poynting vector for a single particle with constant velocity, all the discussiàon bout electrodynamic momentum talks about that.  — Preceding unsigned comment added by 134.158.23.246 (talk) 09:34, 24 June 2011 (UTC)
thread_title:  wrong 

message: Near the bottom the article says "Instead of the flux vector E × B as above ...".  Where does E × B appear above?  (I was hoping to be able to refer to it.) Vaughan Pratt (talk) 02:41, 10 January 2014 (UTC)
thread_title: Where is E × B ?

message: (1) The article defines the Poynting vector S to be "the energy flux vector", rather than giving a specific formula. That is fine. But the definition is not made "out loud", but only implicitly -- one is forced to infer it from the proof of Poynting's theorem. That is not so good.
(2) The main problem I have with this article: it goes back and forth several times between S = E x B and S = E x H, between J and J_f, and between a vacuum and a medium. 
For example, early in the article we hear about "free" current, but then we switch to just E and B, then suddenly we have constitutive relations, but they are merely the constitutive relations of empty space. Then we proceed to derive (to prove) that S = E x H. Then we're told that we really did S = E x B (!!!). This does not match the S = E x H definition given under Poynting vector. 
What is the correct setting for proving the theorem? Do I need to consult a medium, or decide in a vacuum?
(3) At the end we are told that we could have gotten S = E x H, S = D x B, or even S = D x H, and that the content of Poynting's theorem is different depending on what we got. In the words of the text:
It is possible to derive alternative versions of Poynting's theorem. Instead of the flux vector E × B as above, it is possible to follow the same style of derivation, but instead choose the Abraham form E × H, the Minkowski form D × B, or perhaps D × H. 
Choose?
The Poynting theorem we proved here was established independently of these conclusions. It made no commitment as to whether S = E x B or S = E x H. How can the theorem have different versions depending on the formula we later discover for S? Is Poynting's theorem the "continuity"-type statement
where S is defined to be the energy flux, or is it the conclusion S = E x B, where S is defined to be the energy flux? Or is it the formula that's obtained by substituting E x B for S in the boxed formula?
Are the hypotheses or definitions different, to get different theorems? In that case, what are these variable hypotheses? 
Why don't we get S = E x H, like in the article Poynting vector? Or do we?
It seems that the definitions and background assumptions are constantly oscillating back and forth in this article.
178.38.181.216 (talk) 00:44, 24 May 2015 (UTC)
replies: text: Pretty devastating takedown, if I say so myself. Is there such a thing as a C-class article? 84.226.185.221 (talk) 20:47, 15 October 2015 (UTC)
replies: text: There is. I'm going to try to wade through the subject to figure out what the correct form of the equations should be. --Ipatrol (talk) 19:58, 18 October 2017 (UTC)
thread_title:  Inconsistencies throughout article 

message: I'm fairly new here (sorry if I'm wrong) but reading the guidelines for importance scale I think the "low" rating is too low. Poynting's theorem is covered in at least some undergraduate physics degrees (that's actually how I ended up at this page) which would put it comfortably in the "high" category. Griffith's Introduction to Electrodynamics is a standard undergraduate text that discusses it in chapter 8. I would recommend medium after reading the guidelines.
Alich1881 (talk) 23:23, 2 September 2021 (UTC)
replies: text: Agreed PianoDan (talk) 22:22, 2 December 2021 (UTC)
thread_title:  Importance rating