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Since this is supposed to be an intro to this topic, perhaps a mention of what these fields are would be in order? GeneCallahan (talk) 14:26, 16 November 2009 (UTC)[reply]
The topic is the link between electromagnetism and special relativity. The article is not an intro to electromagnetism. I don't think that readers who are not familiar with E-fields and B-fields have any business here, so to speak, sort of, more or less :-)
Anyway, the lead already explicitly wikilinks to the concepts with the phrase "... in particular the electric and magnetic fields ...", directly pointing to the relevant articles. DVdm (talk) 14:47, 16 November 2009 (UTC)[reply]
Oppose -- I would sooner cut the Lorentz transformation laws out of Mathematical descriptions of the electromagnetic field, where I don't think they fit particularly well, and keep them here. I mean, I can understand how maths of em field benefits from Lorentz transformation laws in various formalisms (vector fields, potentials, etc.), but I think the article would be fine without it, just as it is fine without the formulas for Poynting vector, Lorentz force, etc. in various formalisms. Plus the "Interrelationship between electricity and magnetism" section is not part of other articles.
Fun fact: When I made this page many years ago, it was partly in response to arguments with what I call "anti-magnetism fundamentalists". An "anti-magnetism fundamentalist" is someone who says "electromagnetism should really just be called electricity, because it is fundamentally based on only the electric force. The so-called magnetic force is just a relativistic side-effect of the more-fundamental electric force." Well I disagree with this point of view, but there used to be one or two editors who would write little "rants" like this on many magnetism and electromagnetism pages. I wanted to be able to delete those rants and replace them with a generic sentence plus a link to a dedicated article that could discuss at greater length whether or not special relativity proved that magnetism was inferior to electricity. So I made this page. I was expecting debates with anti-magnetism fundamentalists to pop up here but it didn't end up happening. :-P --Steve (talk) 01:33, 21 May 2012 (UTC)[reply]
As said - its becuase of so much mathematical overlap, and I was thinking the history could be added to maths of em field. I have nothing to say about "anti-magnetism fundamentalists"... I will remove all the Lorentz transforms from maths of EM field and add/mix to this article, if its ok... F =q(E+v×B)⇄ ∑ici 14:50, 21 May 2012 (UTC)[reply]
Nice. :-) --Steve (talk) 01:41, 22 May 2012 (UTC)[reply]
If its also ok - I cut and pasted/mixed in the covariant tensor equations from maths of em field to here, as the sections are identical (aside from cgs units in this article), but the one in maths of em field now points to the lorentz transformations which are no longer there (now here instead), and includes some extra detail I presume you think is out of place? If this is not done, the we are unecessersarily duplicating content. The other article used SI units, it may be better to use them here also for familiarity. Revert if you think so. =) F =q(E+v×B)⇄ ∑ici 12:43, 22 May 2012 (UTC)[reply]
Section on non-relativistic form of frame transformation equations for the fields is misleading[edit]
In the section on frame transformations of the fields it gives a list of non-relativistic limiting forms. While these equations are indeed what you get if you let v become very small, the equation for E and the equation for B do not simultaneously obey Galilean Relativity. To have a self-consistent low-speed limiting form you have to use either one or the other, representing the two low-speed physical possibilities of Electro-quasi-statics and Magneto-quasi-statics. A lot of textbooks get this wrong. Here is a good source if we need one:
I should have said that electromagnetism is essentially (Einsteinian) relativistic. So it is not reasonable to expect any version of it to obey Galilean relativity. Or rather, that magnetism would not exist at all, if Galilean relativity were true. JRSpriggs (talk) 06:39, 27 April 2015 (UTC)[reply]
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"Deriving magnetism from electrostatics" - Incorrect statement[edit]
This section states "The chosen reference frame determines if an electromagnetic phenomenon is viewed as an effect of electrostatics or magnetism."
This is incorrect. In the Feynman lectures[1] and textbooks such as[2] uses an infinite straight wire as example, and the analysis is electrostatic as described. But the authors does not claim that this method can be generalized to other cases. And it can't. In all other cases charge carrier velocities must be taken into account, and the angular dependent retarded electric field must be used, when evaluation the fields.
In case on perpendicular motion with respect to an infinite straight wire, the static charge on the wire is zero, and the force arises due to field retardation, and not length contraction.
I have no official references for this, but se the discussion I've started on stackexchange
[2]
David J. Griffiths, Introduction to electrodynamics, third edition, chap. 12.3.1. — Preceding unsigned comment added by MadsVS (talk • contribs) 12:39, 16 December 2019 (UTC)[reply]
Please sign all your talk page messages with four tildes (~~~~) — See Help:Using talk pages. Thanks.
The text is properly sourced, and without other wp:reliable sources we cannot change anything about it. Our own wp:original research about this is not accepted. - DVdm (talk) 13:29, 16 December 2019 (UTC)[reply]
Thank you DVdm. We could remove the statement i refer to. The sources we reference doesn't state that the electrostatic analysis can be used generally, but this page does. I've dissused my results with two professors in SR and GR, and they both agreed, but they don't have time to help me publish. MadsVS (talk) 15:50, 16 December 2019 (UTC)[reply]
I don't see where our article says that the method can be generalized to other cases. The statement itself seems to be adequately backed by the cited sources. - DVdm (talk) 17:15, 16 December 2019 (UTC)[reply]
"The chosen reference frame determines if an electromagnetic phenomenon is viewed as an effect of electrostatics or magnetism."
"An electromagnetic phenomenon" is very general in my ears. It should in principle be "an infinite wire, and only in the case of parallel motion", instead. Feynman show the electrostatic relation for this case only. MadsVS (talk) 19:55, 16 December 2019 (UTC)[reply]
I don't see a real problem with that. This talk page has 13 recent watch visitors, any comments from anyone else? - DVdm (talk) 22:15, 16 December 2019 (UTC)[reply]
DVdm I have found a textbook source that analyses perpendicular motion. [1] I think it would make the page more accurate if this information is included so the readers will not be left with the impression that magnetism can always be derived from electrostatics.
Here is a suggested edit to the section Deriving magnetism from electrostatics with the changes underlined. Let me know what you think.
The chosen reference frame determines whether an electromagnetic phenomenon is viewed as an electric or magnetic effect or a combination of the two. Authors usually derive magnetism from electrostatics when special relativity and charge invariance are taken into account. The Feynman Lectures on Physics (vol. 2, ch. 13-6) uses this method to derive the "magnetic" force on a charge in parallel motion next to a current-carrying wire. See also Haskell and Landau.
If the charge instead moves perpendicular to a current-carrying wire, electrostatics cannot be used to derive the "magnetic" force. In this case it can instead be derived by considering the relativistic compression of the electric field due to the motion of the charges in the wire. MadsVS (talk) 13:29, 24 April 2023 (UTC)[reply]
References
^Purcell, E. M.; Morin, D. J. (2013). Electricity and Magnetism. Cambridge university press. pp. 265–267. ISBN978-1-107-01402-2.
@MadsVS: Apart from the scare quotes around magnetic, it looks good to me. - DVdm (talk) 23:22, 25 April 2023 (UTC)[reply]
@DVdm Great. I will make the edit, and remove the scare quotes it the original text as well, so it is consistent. In line 5 in the introduction I will also substitute "electrostatic" with "electric". MadsVS (talk) 08:01, 26 April 2023 (UTC)[reply]
@MadsVS: I made some style-related tweaks to the ref and added a direct link to the relevant page in the book: [1], [2]. - DVdm (talk) 10:32, 26 April 2023 (UTC)[reply]
Beautiful! Thank you so much for your help @DVdm MadsVS (talk) 17:37, 26 April 2023 (UTC)[reply]
Can someone mention in the article if the equations here are in SI or CGS? — Preceding unsigned comment added by Zlelik2000 (talk • contribs) 19:05, 10 March 2021 (UTC)[reply]
Removing the claim that the Lorentz transformation of the fields is "also called the Joules-Bernoulli equation"[edit]
This claim was first added on 27 March 2010 by '186.136.83.209', in other words, a user without an account. The addition of that claim was the only change made in that edit, and it was provided without any references. All this—an anonymous user; this being the only change; no references—is already suspicious. Since then, no one has added any references for this claim. Indeed, there is little doubt that the claim is, in fact, false. This is for several reasons, to be discussed shortly.
Motivation for this write-up: appearance of the incorrect name in published papers and theses
The incorrect name "Joules-Bernoulli equation" (sometimes "Joule-Bernoulli equation") has, since 2010, appeared in at least five published papers and six theses (doctoral, licentiate, or master's). They all either use it without reference or provide a reference that itself doesn't use that name. Therefore it is a near certainty that the authors used the incorrect name they found on Wikipedia. The fact that the incorrect name proliferated from Wikipedia to published papers and theses is my main motivation for putting a bit of effort into this write-up.
Here are the papers and theses I have been able to locate that use the incorrect name.
For completeness, I will also mention the following two papers, even though I found multiple aspects of each one to be eyebrow-raising (as far as content, copy editing, and mathematical typography):
Page 3 of this one, citing Ref. 11. This reference is T. L. Chow, Introduction to Electromagnetic Theory: A Modern Perspective (2006), which does not use the name "Joules-Bernoulli equation." (In the paper, the textbook's author's last name is misidentified as Tai, which is actually the first name, but helpfully the ISBN is included in the reference.)
Page 48 (bottom) of this paper, citing Ref. 17, which is again the textbook by Chow.
In addition, the false name also appears in two Physics StackExchange answers, in both cases without reference (here and here).
Reasons for doubting that the equations are called the "Joules-Bernoulli equation" (or "Joule-Bernoulli equation")
History of the development of the Lorentz transformations doesn't record significant contributions of anyone named either Bernoulli, or Joules, or Joule
As a first step, if you check the Wikipedia article on the history of Lorentz transformations, you will notice that there is no mention of anyone by the name of Bernoulli,Joules, or Joule.
Even the most recent well-known scientist or mathematician named Bernoulli died much too early to have been involved
Again, let's start (but not end) with Wikipedia. If you look at the list of people named Bernoulli, you will notice that the last famous person so named, and who was a scientist or a mathematician, died in 1807, way before Maxwell's equations or Lorentz transformations were discovered.
To confirm, we can look at the Dictionary of Scientific Biography. It is available online, but behind a paywall. I have access to it, and I searched for the keyword "Bernoulli." It returned the same eight Bernoullis that Wikipedia lists:
Bernoulli, Johann (Jean) I (b. Basel, Switzerland, 6 August 1667; d. Basel, 1 January 1748) mathematics
Bernoulli, Johann (Jean) II (b. Basel, Switzerland, 28 May 1710; d. Basel, 17 July 1790) mathematics.
Bernoulli, Johann (Jean) III (b, Basel, Switzerland, 4 November 1744; d. Berlin, Germany, 13 July 1807) mathematics, astronomy.
Bernoulli, Daniel (b. Groningen, Netherlands, 8 February 1700; d. Basel. Switzerland, 1 March 1782) medicine, mathematics, physics.
Bernoulli, Jakob (Jacob, Jacques, James) I (b. Basel, Switzerland, 27 December 1654; d. Basel, 16 August 1705) mathematics, mechanics, astronomy.
Bernoulli, Jakob (Jacques) II (b. Basel, Switzerland, 17 October 1759; d. St. Petersburg, Russia, 15 August 1789) mathematics.
Bernoulli, Nikolaus I (b. Basel, Switzerland, 21 October 1687; d. Basel, 29 November 1759) mathematics.
Bernoulli, Nikolaus II (b. Basel. Switzerland, 6 February 1695; d. St Petersburg. Russia, 31 July 1726) mathematics.
We see that the most recent one was Johann III, who died in 1807. That was much too early to have been involved in the development of the Lorentz transformations of the electric and magnetic fields.
No well-known scientist was named Joules
This is confirmed by the fact that 1. there is simply no person so named with a Wikipedia article, and 2. searching for Joules in the Dictionary of Scientific Biography returns no hits.
No one named Joule was involved
Wikipedia has pages for two people named Joule: the famous James Prescott Joule, and John Joule, a still-living chemist. A search in the Dictionary of Scientific Biography only returns the former. John Joule was born way too late (got his PhD in 1961) and is active in much too unrelated a field (heterocyclic chemistry) to have had any chance to significantly contribute to the development of the Lorentz transformations. James Prescott Joule, on the other hand, was alive at about the right time (died in 1889) to be able to contribute to the beginnings of the development of the Lorentz transformations. However, the fact is that he didn't; the articles about him on Wikipedia and in the Dictionary of Scientific Biography make no mention of any activity relevant to the development of the Lorentz transformations of the electric and magnetic fields.
No textbook on electromagnetism (including the best-known ones) mentions anything called either the "Joules-Bernoulli equation" or the "Joule-Bernoulli equation" (or any permutation thereof)
I have checked the following textbooks—all of which treat the Lorentz transformations of the electric and magnetic field—to see if any of them mention anything called the "Joules-Bernoulli equation" or the "Joule-Bernoulli equation." In fact, I looked at whether they mention "Bernoulli," and if so in what context, and then whether they mention "Joules" or "Joule". In each book, I also checked the text surrounding the equations for the Lorentz transformations of the and fields.
A few textbooks treat covariant electrodynamics, but don't provide explicit transformation equations for the fields. For completeness, I checked them anyway:
Jefimenko, Electricity and Magnetism: An Introduction to the theory of Electric and Magnetic Fields, 2nd ed. (1989)
Thidé, Electromagnetic Field Theory (2000)
Susskind and Friedman, Special Relativity and Classical Field Theory (Theoretical Minimum) (2017)
Bettini, A Course in Classical Physics 3: Electromagnetism (2016)
Baylis, Electrodynamics: A Modern Geometric Approach (2002)
Garrit, Electricity and Magnetism for Mathematicians: A Guided Path from Maxwell's Equations to Yang-Mills (2015) (treats the connection between electromagnetism and special relativity, but stops short of giving full covariant treatment)
Page, An Introduction to Electrodynamics From the Standpoint of the Electron Theory (1922) (different from the rest, but covariant)
Page and Adams, Electrodynamics (1945; reprinted in 1965) (similar to the above)
Kip, Fundamentals of electricity and magnetism (1969) (treats the connection between electromagnetism and special relativity, but stops short of giving full covariant treatment)
In addition, again for completeness, here is a number of textbooks—some of them well-known—that don't treat the Lorentz transformation of the electric and magnetic fields at all:
Saslow, Electricity, Magnetism, and Light (2002)
Holt, Introduction to electromagnetic fields and waves (1967)
Peck, Electricity and Magnetism (1953)
Kelly, Electricity and Magnetism (2015)
Nelkon, Electricity and magnetism (1952)
Prytz, Electrodynamics: The Field-Free Approach: Electrostatics, Magnetism, Induction, Relativity and Field Theory (2015)
Irodov, Basic Laws of Electromagnetism (1986)
Loeb, Fundamentals of Electricity and Magnetism, 3rd ed. (1947)
Ramsey, Electricity and Magnetism: An Introduction to the Mathematical Theory (1937)
Tewari, Electricity and Magnetism, Rev. ed. (2011)
Ball, Maxwell's Equations of Electrodynamics: an explanation (2012)
Fleisch, A Student's Guide to Maxwell's Equations (2008)
Crowell, Electricity and Magnetism, 2.3 ed. (2006)
Harnwell, Principles of Electricity and Electromagnetism (1949)
Whitehead, Electricity and Magnetism: An Introduction to the Mathematical Theory (1939)
None of these textbooks mention anything named either the "Joules-Bernoulli equation" or the "Joule-Bernoulli equation." Indeed, few of them mention Bernoulli at all; those that do, mention it in contexts that have nothing to do with Lorentz transformations. In particular, the last two chapters of Feynman's book are on the physics of fluids, including a discussion of Bernoulli's principle (which Feynman calls Bernoulli's theorem); Kelly also mentions this, although under the name "Bernoulli's equation"; Davidson, in a chapter on magnetohydrodynamics, mentions Bernoulli′s function; Chaichian et al. deal with "Bernoulli’s equation in relativistic magnetofluid dynamics"; Jentschura mentions Bernoulli polynomials and Bernoulli numbers; Heald and Marion mention that Jacob and Daniel Bernoulli were the first to study special cases of that which later came to be known as Bessel functions; Brau mentions that the calculus of variation started with Johann Bernoulli's challenge to his brother Jakob; Wegner says that "Daniel Bernoulli conjectured that there might be a -law for the electrostatic interaction"; Coey states that Daniel Bernoulli "promoted" the horseshoe magnet.
None of the books mention anyone named Joules. On the other hand, Joule is mentioned in many of them, but only in the context of the unit of energy, and also Joule heating. Only Coey mentions him in the context of magnetostriction.
A general Google search for the "Joules-Bernoulli equation" or the "Joule-Bernoulli equation" returns only unrelated independent hits
I conclude that the edit of 27 March 2010 by '186.136.83.209' was either an honest mistake or—more likely—an act of vandalism. One way or another, that incorrect edit has now been reverted (after almost 13 years!). Reuqr (talk) 22:33, 15 February 2023 (UTC)[reply]