Talk:Electromagnetic field/Archive 1

Archive 1

E-M Puzzle

Let's say a charged particle moves from point A to point B. It was initially at rest at A, then it suddenly accelerates, moves to B, then decelerates suddenly to stop at B. The electric field around the charge has to change to become centered at its new position. But it cannot change instantaneously throughout all of space because doing so would send information at a speed which is faster than light. So an electromagnetic wave is emitted which has the effect, after it dissipates, of recentering the electric field.

Now, if a charge is moving inertially at a given velocity and then suddenly accelerates to a new velocity but then stays moving inertially at that given velocity, then an electromagnetic wave is transmitted. This is called bremsstrahlung. This is what happens to electrons encountering the ionosphere: they decelerate and produce polar auroras.

If an charged particle is at rest, then it is surrounded by an electrostatic field which is symmetric in every direction. But what if the charge is moving inertially at a constant velocity? Then from its own frame of reference, it is surrounded by an electric field which is static, the same in every direction, without the presence of any magnetic field. But seen from a different frame of reference, the charge is moving, and the electric field has to move along with it, and this is where the problem sets in. If the charge moves along the x-axis, then let's say it moves from x₀ towards the "right" to x₁ during a unit of time. Point x₂ lies directly in the particle's path. The electric field will point, say, away from the proton, and during the unit of time its magnitude will increase. This increase of the electric field at point x₂ will cause a circular magnetic field line to be induced, which can be thought of as the rotation of a "magnetic fluid", and the "angular momentum" vector of this rotation points in the direction of the proton's velocity. Then, say there is a point x_-1 behind the moving proton. It has an electric field vector pointing in the negative direction, and in one unit of time its magnitude decreases. This means that the electric field vector at point x_-1 has increased in the positive direction, thereby inducing -- again -- a circular rotation of the magnetic fluid around it, such that the angular momentum vector of the rotation points in the direction of the proton's velocity.

Therefore the proton, when moving at constant velocity, is surrounded not only by a spherically-symmetric electric field which moves along with it, but also by a cylindrically-symmetric magnetic field whose axis of symmetry parallel to the velocity vector of the proton. Both of these fields decrease in magnitude inversely with the square of the distance. But what does this imply? At any point not directly in the proton's path, there is going to be a magnetic field vector which is perpendicular to the electric field vector. This means that there is going to be a Poynting vector at that point in space.

Points which lie on a transversal plane (perpendicular to the velocity) which includes the charge itself, will have Poynting vectors parallel to the velocity vector, and pointing in the same direction: forwards. Points on transversal planes which are in front of the charge will have Poynting vectors which will also be pointing not only forwards but also inwards towards the path of the charge. Points behing the charge will have Poynting vectors which point not only forwards but also away from the charge's path.

Poynting vectors are associated with electromagnetic waves: they indicate the direction of propagation and the power (rate of energy movement). A proton moving with constant velocity would have Poynting vectors which point in directions tangent to concentric spheres whose centers are the proton. These spheres move along with the proton. These Poynting vectors also all belong to planes which pass through the proton's path. The magnitudes of these Poynting vectors would vary as the fourth power of distance (?). What all these vectors do is to move energy in the direction of the proton. The electric field surrounding a static charge stores energy: this energy is proportional to the magnitude of the electric field vectors. When a charge moves at constant speed, the electric field around it has to move along, somehow, to keep up with its source. This implies a movement of electric energy, and the speed of this movement is power: hence the Poynting vectors.

But if these Poynting vectors describe E-M waves then these must be very unorthodox E-M waves, because they appear to move on the surfaces of spheres, starting all from a single point behind the charge and converging all again at a single antipodal point in front of the charge. Besides, the E and M fields moving along with the particle do not appear to oscillate at all, as would be expected of E-M waves.

Then, what happens if like charges are strung along a line which extends infinitely. If these charges move along their line, then they collectively form a current, even though the charge density remains constant. The constant charge density extending in an infinite line implies a cylindrically-symmetric electric field centered around the line, but the moving charges also imply a cylindrically-symmetric magnetic field. The magnetic field lines are circles whose centers are points on the line of the current. This can be seen to be a consolidation of the one-particle case, but is now equivalent to Ampère's law. Now the Poynting vectors are all parallel to the direction of the current, no matter where they are located in space. This would appear to imply that there are E-M waves moving parallel to the current; but then again, there are no oscillations of the E-M field. Perhaps these E-M waves are "degenerate", or "frozen". By the way, this is an example of a magnetostatic field. --AugPi 10:12, 3 Apr 2004 (UTC)

Three years pass...

On your penultimate paragraph about the non-oscillating field. You are forgetting about the time-varying nature of your field. Your proton started from rest, suddenly accelerated, translated, and then suddenly decelerated. If you do a Fourier analysis on the field over time, you will find that it is composed of an infinite spectrum of oscillating EM waves that conveniently add up to a rectangular or trapezoidal pulse in time. It's the three-dimensional version of calculating the Fourier spectrum of a square or trapezoidal pulse waveform.

On your final paragraph, I put it to you that your infinite line of moving charges does not constitute a current. Consider what happens in a plane perpendicular to the line in a given interval of time. At the beginning of the interval, there are an infinite number of charges on the left of the plane and an infinite number on the right. During the interval, let's say ten charges cross the plane from left to right. You are then left with infinity minus ten charges on the left, and infinity plus ten on the right. The current that flowed is then the difference between these two undefined quantities. I'm not going to blaspheme against mathematics by attempting to perform the subtraction. You might say that "infinity plus ten" is an absurdity, but it is a deliberate absurdity that I created to explain why it is meaningless to talk about a current flowing in your example. I think that, as far as the universe is concerned, a current requires a change in the distribution of charges throughout the volume in question, and such a change is not occurring in this case.

I look forward to reading your reply in the year 2010. :-) --Heron 15:07, 28 May 2007 (UTC)

Peer Review: Fluid analogy

It is nice to see a fresh treatment of a well-known subject. To balance this point of view, the two-fluid analogy should also treat the relationship of the two fluids to each other; we should see how B turns into E and vice versa, in an eternal harmonic motion. The fluid analogy, in fairness to Maxwell's equations, should encompass this.

LePage had a nice model as well. It is not fluids, but the encyclopedia, if it exposes the fluid model, needs to set LePage's viewpoint out as well, for balance.

Also, Faraday's contribution, that the fluids were somehow viscous or rubbery and hence exerted force on the charges.

Also, what about the freeway analogy, which uses the irrotational nature of Maxwell's equations: ie the travel of cars on a freeway obeys Maxwell's equations as well! (covariant motion)

Also, what about Purcell's viewpoint that an electromagnetic field is 'something that crackles'. 169.207.89.249 19:37, 3 Jan 2004 (UTC)

It seems clear that as a front of electrical fluid propogated away from a positive source charge, its velocity of propogation would decrease, which in turn would induce a magnetic field. Is this correct? As someone who doesn't understand EM concepts very well, I think the entry needs to explore in more depth the implications of the fluid analogy.

The velocity of the moving "particle" of fluid, ${d\mathbf {v} \over dt}$ would decrease indeed, but the velocity field itself would remain constant:

${\partial \mathbf {v} \over \partial t}=0$

The velocity field changes when the particle moves, and when this happens, accelerating electric fluids induce movement of the magnetic fluid, and vice versa, so an electromagnetic wave is propagated. The net effect of this EM wave is to change the velocity field throughout all of space so that it is centered at the new position of the charge. (Imagine changing the position of a Persian rug by lifting one side of it up, then slamming it back down: a wave propagates through the rug, and by the time it reaches the other end, the rug has changed position slightly.) --AugPi 04:28, 24 Mar 2004 (UTC)

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The fluid analogy does not work in this sense: that objects immersed in a moving fluid (e.g. a river) tend to be pushed by that fluid in such a way that the velocity of the object aligns with the velocity of the fluid. Once the velocities are aligned, the fluid's motion should vanish from the object's point of view.

However, the force of an electric field on a charged particle is $\mathbf {F} =q\mathbf {E}$, and this force is independent of the velocity of the particle, which means that the particle will accelerate continually in the direction of the field. If the field is the velocity field of a fluid then the fluid would be causing the object to accelerate continually in the direction of the fluid's motion, to the point that the object's speed becomes way larger than the fluid it is immersed in. This is paradoxical.

From the continually accelerating object's point of view, if its speed has already surpassed the speed of the fluid, then the fluid is moving backwards, so the field should be pointing in the direction opposite to the direction in which the object keeps accelerating. This means that that the object should stop accelerating and begin decelerating, until its speed aligns with the speed of the electric fluid.

An alternative interpretation would be that the field is not actually a velocity field, but a density field of photonic fluid, which is constantly moving at the same speed: the speed of light, independent of the speed of the observer (the charged object). Photonic fluid never changes speed but can change net direction and the intensity of its net movement in that direction. This interpretation would have to be verified by someone who knows QED. --AugPi 02:48, 24 Mar 2004 (UTC).

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I just noticed this page listed on the "Peer Review" page, and thought I might add some comments. All these of course, are to be understood as prefixed with "IMHO". The article seems to have a lot of discussion on the fluid analogy and other analogies, so my comments are regarding this aspect.

• The article currently has lots of analogies for the electromagnetic field, but very little discussion of what actually the electromagnetic field is. While analogies are useful upto a point, there is always the risk of getting too excited about them and forgetting to describe something for what it is, rather than what it is similar to.

• As to writing about "what the electromagnetic field really is", the best description, and in a sense the only honest one, is in terms of the field equations. Everything else, analogies, explanations etc. are only attempts to get a 'feel' for these equations. Therefore, a suggestion : the article currently is extremely verbose - it might help if one came up with a leaner, more equation-filled version. The example I have in mind is Maxwell's equations which IMO is now a very decent article.

• Further about analogies : analogies to fluids etc. make sense only when the equations for fluid flow and for the EM field are the same. This happens most transparently in the following cases

In the continuity equation for the electric charge density, where the charge density in EM and the mass density of a source-less fluid are analogous

In the divergence equation for the magnetic field, where the magnetic field and the velocity field of an incompressible fluid are analogous.

Cooking up analogies for the other Maxwell equations seems to lead to some unnecessary obfuscation; and while I am sure it can be described in terms of the interaction of two fluid velocity fields ("electric" & "magnetic" fields), most people who will read the article will not be experts on the fluid dynamics of two (quite weirdly) interacting fluids.

• Regarding the "density field of photonic fluid" : the electric field is not a photon density -- the correct field is more like $\ n(\omega )={\frac {1}{2}}{\frac {\epsilon E(\omega )E^{*}(\omega )}{\hbar \omega }}$.

To summarize : There is no point pushing the fluid analogy this far - it seems to be hiding more relevant ideas.

[[User:AmarChandra|Amar | Talk]] 17:18, Jun 30, 2004 (UTC)

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I think the fluid analogy in this article hurts more than helps. Most people have a strong intuitive sense of how a fluid should behave, and EM fields do not behave like fluids. They behave like force fields. The article currently relies so heavily on the fluid analogy that I think some people will be confused into thinking that there actually is a ethereal fluid of some kind that makes these processes work, which is not true at all (as far as we know).

I think a better approach would be to help people form an intuition about what a force field (vector field) is. This article is crying out for diagrams; two or three pictures would greatly enhance any verbal explanation. I will try to contribute more specific ideas later as time permits. -- Beland 04:04, 4 Jul 2004 (UTC)

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Some comments:

• I agree that there is too much emphasis on the analogy compared to what EM field is in the current version of the article.
• I wouldn't mind having a shorter article on EM field, with links to other well established articles
• I would suggest to create a section "Simple analogies to understand the EM field". It would introduce the subject, then list the various analogies that have been used. Each one would have its own article. This way, the balance between what EM field is, and what it looks like would be more adequate, and there would be plenty of room to describe the analogies.
• I would suggest to introduce the subject by saying that analogies have been important in the history and development of electromagnetism. As an example, the first model of EM was the "tube of force" of Faraday, which did not have any mathematical underpinnings. Maxwell was later very interested in this analogy, which helped him develop his equations. (source: The strange story of the quantum, Banesh Hoffmann, page 10)

Hope it helps... Pcarbonn 20:13, 13 Jul 2004 (UTC)

Cleanup required

The article contains a lot of useful and important information. The presentation could be improved, however; for example, the notation is undefined in places (although it's obvious to those familiar with the notation). Also, there really should be a section on the maths describing the EM field (which should discuss the various formulations, e.g. vector field structure, as compared to the tensor field approach, quantum formulation etc...). MP (talk) 13:45, 4 December 2005 (UTC)

I tried a bit :) --Electron Kid 17:25, 23 December 2005 (UTC)

Major rewrite

I have rewritten the article to give more focus on the em field itself, rather than the fluid interpretations (which are not that important). However, as a courtesy to the work of other editors, I have moved the bulk of the fluid interpretation work to a new article: hydrodynamic interpretation of the electromagnetic field. Some of the new sections that I've added, for example, 'Relation to and comparison with other physical fields' and 'Everyday applications' still need to be expanded. I also believe that the 'See also' list is too lengthy and only the most directly relevant links to the em field should be kept. MP (talk) 11:16, 4 April 2006 (UTC)

Here's an idea. Perhaps the extremely long list of links in the 'See also' section can be incorporated into the 'Applications' section. MP (talk) 09:20, 23 April 2006 (UTC)

Hydrodynamic interpretation of the electromagnetic field has been deleted by now as original research, see Wikipedia:Articles for deletion/Hydrodynamic interpretation of the electromagnetic field. I've also deleted remains "Other descriptions of the electromagnetic field" here [1]. If someone wants to salvagd something important and correct, go ahead.

The focus of the article is most unclear to me, we have Electric field, Magnetic field, Maxwell's equations. Which aspect should be coverered in Electromagentic field?

Pjacobi 06:27, 9 May 2006 (UTC)

As to the focus of the article, the issue there is that in order to describe an electromagnetic field, you need to talk about electric fields, magnetic fields, and Maxwell's equations, which are respectively the two components of the combined electromagnetic field and the equations desribing its behavior. DAG 14:51, 9 May 2006 (UTC)

The fluid analogy is very doubtful at the least and plain artifical and false at worst. In fact it was the entire fluid and corresponding ether debate in the 19th century that caused great confusion back then and apparantly still now, and for what? It is all so unnecessary. The governing dynamical equations of hydrodynamics with the equation of state bears no resemblence at all to maxwell's equations. EM waves are transversal, HD waves are longitudinal. Better leave that analogy out entirely, for it is at most of only historical significance and is but a hindrence to actual understanding.

This article could still benefit from a major rewrite IMO, in which what EM truly is should be paramount, namely an abstract mathematical field whose sources are charged elementary particles. Albester 12:35, 10 May 2006 (UTC)

Woaw ! Hold your horses! The EM field is 'an abstract mathematical field whose sources are charged elementary particles' - that statement is loaded wih inconsistencies, one of which is that if it's a mathematical field, then you can't mix that with physical concepts such as elementary particles. The EM is physically REAL and not just a mathematical concept - we only use the maths to formulate the theory precisely and test the theory against experimental results. If the EM field was a purely mathematical thing, then you can't really explain much in physics (such as the stablility of particles etc...). MP (talk) 12:30, 11 May 2006 (UTC)

Mpate thanks for your input. What you say is correct, there are certain problems with the mathematical description in the classical sense. The infinite self energy of point charges was a bit of an embarrasment in the 19th century. What I am trying to say is that the EM field is a mathematical construct, because classically speaking only the forces on particles are measured, but the fields prove to be an eloquent and very fruitful concept in dealing with problems and in understanding.

Of course I don't deny, it must even bo so!, that the basis are experiments conducted by Ampere and Faraday and the likes, and that the final theory created by Maxwell give all these experiments a unified theoretical framework in terms of the EM field.

Now, if you look at the theory, the macroscopic Maxwell equations, the only link you see that has any bearing on elementary particles at all is the charge. This isn't much of a problem at all since the theory has little to do - an sich - with elementary particles or even advanced quantum mechanical questions about particle stability, just as long one realises the range of validity of the theory, namely large number of photons whose impulse is small compared to that of the mechanical system.

It only remains how to rewrite this article. Personally, I would not at first start off by talking about photons and particles and stability of particles since thats a wholly different subject that very quickly enters the quantum electrodynamical domain. I suggest to focus on the experimental discoveries and verifications and than on to Maxwell's equations, Langragian formulation of fields and its transformation properties (E and B fields exists as one entity really, speaking about E or B fields individually implies a frame of reference). Albester 06:39, 13 May 2006 (UTC)

Maxwell-Hertz relations ?

I don't know what are these Maxwell-Hertz relations, which you refers to in the article ; are they the expression of Maxwell equations in the free space (with $\rho =0$ and $\mathbf {J} =0$ ) ?

Almeo 10:01, 25 May 2006 (UTC)

From the looking I've done, it's either that, or they're the equations everyone calls Maxwell's equations, which are actually a simplified form of Maxwell's original equations (which were apparently given in terms of quaternions, vector math not having been really developed yet). It could be either, as far as I could tell. I'll see if I can't look harder later. ;) DAG 20:15, 25 May 2006 (UTC)

Table comparing interactions

I've copied the table from fundamental interaction and placed it in this article in the relevant section. The table gives a brief summary of comparing the 4 forces, but I'd like more details of the EMField (as compared to the other fields) in the form of a short description, just like the (incomplete) one I've given for EM and gravitation. I think there should also be some comparison of the field equations (not necessarily stated explicitly) - maybe the table could be extended to accommodate this. Just a few ideas. Comments appreciated. Thanks. MP (talk) 21:18, 10 June 2006 (UTC)

Examples in the Latest Edit

If you've been keeping track of this page, I'm sure you'll notice the somewhat largish edit I made. The biggest (but not the only) part of it was the addition of two examples showing how the EM field tensor transforms under a Lorentz transformation. I feel that the examples can help enlighten people, but I do have my concerns, so I thought I'd voice them here. Firstly, is the component by component listing of the computation too much or too long? Should the terms that are zero straight out be left out? Or should the whole of that be removed, and left as a so called exercise for the reader? Or is it fine as it is? Secondly, should the examples be there at all? On the one hand, I feel they help illustrate how fields can change due to a Lorentz transformation. On the other hand, people might not care, or might want it in a separate article or something. So, thoughts on that? I guess there's a third thing, which has to do with my addition to the section on the tensor formulation vis-a-vis Maxwell's equations. Basically, I just briefly added in some comments saying which of the traditional equations came from where. Should this be expanded upon to show explicitly how Maxwell's equations come out? Anyway, let me know what you think. Muchas gracias. DAG 09:14, 16 June 2006 (UTC)

Hi DAG. You have raised some good questions. I was also wondering whether there was too much mathematical detail before the edits you made. I rewrote this article some time ago and want to read through the article properly. But at the moment, I think the transformation equations could be kept in the article. If things get too mathematical, then maybe we can create a new article to place the maths into. MP (talk) 10:37, 16 June 2006 (UTC)

More Edits...

I made two more edits. The first beefed up the section on the vector formulation somewhat, adding some discussion on the compatibility of Maxwell's equations with special relativity and such. The second, more substantial, was that I added a section on the potential formulation of Maxwell's equations. I felt that, given the inclusion of the other two formulations, this one deserved a place. My one big concern is kind of structural, in that towards the end I put a lot of equations inside a paragraph where they kind of break it up visually. But I felt (at the time at least) that that was the best way to include that info. Any ideas or comments on that? Or anything else? DAG 08:10, 17 June 2006 (UTC)

Apparent Revert?

I don't suppose I could ask why User:Sinniko for all intents and purposes the article was more or less reverted to how it existed at the end of June 5 (specifically more or less to the edit on 12:51, 5 June 2006 by 217.250.90.165, with the only difference being the apparent addition of a space)? I'll admit some of what I added was long and such, which is why I asked for comments and suggestions here, but I also think that some of the stuff was worth having in there, at least briefly (which I'll admit I am anything but). If you're reading this Sinniko, could you explain what you thought was wrong with it so that we can move forward and continue improving it taking your thoughts into consideration? Thanks. DAG 10:49, 17 June 2006 (UTC)

It's simply sock puppet vandalism. See Wikipedia_talk:WikiProject_Physics#Certainty_principle (scroll down). You can revert on sight. Zarniwoot 11:48, 17 June 2006 (UTC)

Incomplete sentence?

"Indeed, it is believed by many that reconciling certain apparent coincidences in how two different observers moving relative to each other can explain the same effect with different explanations" seems to be an incomplete sentence.

Yeah, rereading it, I decided to scrap it and rewrite it. Is the new wording better? DAG 09:14, 27 June 2006 (UTC)

Thanks to whomever went through and removed all my "it should be noted"s... I have some bad writing habits, at least in the Wiki-sense...  :/ :) DAG 18:31, 14 July 2006 (UTC)

Conceptual accuracy, ultra nit-picking

It took me a long while before I realized that all our descriptions of physical forces are not actually descriptions of the forces, but descriptions of the math and logic of the theory. To use the tried and possibly true analogy; the theory is the map, and not the terrain. Thus when we say that EM is this or that, we're not actually talking about EM itself, but something which is three degrees of separation away from it.

And this is important, and more importantly, not obvious for a layman. No teacher I've ever has even hinted at this. For a student seeking to understand nature, this is a huge obstacle.

I'll let it be an excercise for the reader to draw their conclusions from this. And I'm hoping "damn troll" ain't one of them. I'm quite serious. --Ceriel Nosforit 20:49, 19 July 2006 (UTC)

Yes, you're right. It is assumed that people know this, but of course it needs to be emphasised when beginning to learn theories. MP (talk) 11:38, 20 July 2006 (UTC)

Please add this

http://www.niehs.nih.gov/emfrapid/booklet/basics.htm This web page contains lots of information about emf, can well include some of it in the wiki, and in such a way as it is as easy to understand as in that article without annoying anyone more expeacned who is after equations and such?

I made an edit refering to http://www.niehs.nih.gov/emfrapid/booklet/basics.htm Whereby it states that electric feilds are made from current and magnetic fields from voltege, the article had it the other way around, however It may still be wrong as the "moving" and "not moving" bits may now be the wrong way around? Could someone look to see if this is the case?

Is this article a bit to simerlar http://en.wikipedia.org/wiki/Electromagnetism possibly needs a merge?

I see this was moved to the bottem of the page? Alan2here 18:49, 21 January 2007 (UTC) (sorry I forgot to sign the first time)

Hello there. I moved it to the bottom. Reason: Every new topic on a talk page is placed at the bottom of that talk page. It's not that I think your contribution is unimportant - just that it's the way we do things here to maintain a correct order. Cheers. MP (talk) 09:58, 24 September 2006 (UTC)

Thanks Alan2here 19:09, 27 September 2006 (UTC)

Hey, just adding detail here about why I reverted your edit. The electric field is made from voltages, which are caused by the presence of charges (whether they're moving or not). The magnetic field is caused by currents, which are basically moving charges (a current is defined, more or less, as how much charge moves past a point per second. As to this article and Electromagnetism, there are subtle differences in what they discuss. This article deals more with how math and physics describe the electromagnetic field, while the electromagnetism article seems to deal more with the history of the science behind the electromagnetic field and how that science fits into the larger framework of physics. So they're different, but not unrelated. I suppose you could do a merge on them, as they definitely complement each other much more than they duplicate each other, but the result would be just a bigger article. Probably the best answer would be to better define each article, and then link to the other one more prominently with a good explanation of why one article might be better than another. Or something else. I don't know. DAG 18:23, 24 September 2006 (UTC)

May be too difficult to comprehend for an ordinary person.

This article, In my opinion, is too difficult to comprehend for users of wikipedia who have not learned advanced physics and maths. For example, just reading the first paragraph confuses me even more than before I read this article. Also, the mass majority of the population would like a brief description of the electromagnetic field in something close to layman's terms. I understand that this may not be crutial, but it will certainly help. I thank whoever reads this for their time and attention in this matter.

I agree. I rewrote this article somne time ago and was not happy with my rewrite (even though it was much better than the previous version). The problem is that it can be tricky to give a general overview of this topic to laypeople (not that it's impossible, just that it takes a lot of thought and effort to get it right) as well as including the technical details in the right places (and not overdoing the technicalities). I want to rewrite the article again, once I find the energy to do so. Thanks for the reminder - it always helps when people are reminded that an article is not suitable for nonspecialists. It keeps us on our toes. Cheers. MP (talk) 20:32, 22 January 2007 (UTC)

As for the opening sentence of the article, it is plain wrong. The electromagnetic field is not a region of space (classically or quantum mechanically). This shows just how bad the article has become. MP (talk) 20:35, 22 January 2007 (UTC)

I also agree, I have a big problem comprehending even the gist of the article as a non-scientist. The article could start a lot more gently, and say something pointing me in the right direction, either in this or Electromagnetism. It doesn't say anywhere "Light is electromagnetic radiation" - which is something encyclopaedic which I would like to know. Of course I do know that, but a regular person would look at this and the only thing they could relate it to is solenoids, if they knew about them. I don't know enough to accurately state this, but somewhere in either of these articles we should relate this phenomenon to reality. That would be the job of an encyclopedia (rather than a science textbook). The equations and so on are fine, I can't read them, but a bit of grounding would be a great addition. --General Miaow Say Hello! 13:56, 20 July 2007 (UTC)

Discussion of Possible Health Effects?

Some readers will arrive at this page because they are interested in learning about the possible health risks associated with exposure to electromagnetic fields, an issue that has been the subject of voluminous and inconclusive research. This page should contain a (non-technical) overview of the research results.

The word 'inconclusive' tempts me to launch into a rant about the meaning of science, but I will pretend I didn't see it and agree with you that, seriously, we need some sort of link to the information you are looking for. I'll put on my tinfoil hat and see what I can find. --Heron 15:34, 28 May 2007 (UTC)

We now have a section on Health & Safety, which I hope will lead to the research you are looking for. --Heron 16:19, 28 May 2007 (UTC)

The following paragraph from this section seems questionable:

One of the most common places EMFs can be found is near power lines which have both voltage and current running through them. Power = voltage times current, or, P = VI. Therefore if power needs to be increased, in order to ensure proper health and safety, the current should be changed accordingly rather than the voltage in order to decrease the danger of EMF caused by increased voltage.

Since the main advantage of AC current in power lines is to reduce power loss by decreasing the transmitted current, this suggested solution seems a bit silly. Probably should be deleted as "original research". I would do it myself but decided to ask first since EMF health edits may be potentially controversial. --New 20:36, 19 September 2007 (UTC)

Okay, I deleted the offending paragraph. Also cleaned up the next paragraph which appeared to suggest a stronger stance by NIOSH than justified by the citation. New 21:50, 2 November 2007 (UTC)

with merge in mind

Someone please look at the articles http://en.wikipedia.org/wiki/Electromagnetism and http://en.wikipedia.org/wiki/Electromagnetic_force with merge in mind. Im shure we don't need thee verry simerlar articles. Alan2here 15:59, 20 November 2006 (UTC)

Major rewrite

I have made an attempt at better organising the material in the article. Given the plethora of maths in the article (much of which is unnecessary for the general reader to wade through, as it can be found elsewhere and is not really needed to understand the basics as presented in the article), I have decided to create a new article - Mathematical descriptions of the electromagnetic field - where the maths can be discussed in as much detail as one wishes. In the present article, I propose that a general overview of the mathematics of the EM field be given - mention vector fields, potentials, tensor fields, lagrangians, and the quantum stuff and indicate the purposes of the different approaches (e.g. vector field approach was historically the first one, then SR came along and now we use tensors, with QFT etc...).

I strongly suggest that the Lorentz force law be given a separate section, as it describes the basic (classical) approach to describing electromagnetic interactions. MP (talk) 18:58, 27 January 2007 (UTC)

Serious problem

The issue of vandalism and reversion has reared it's ugly head again. The 'Revision as of 04:51, April 18, 2007 (edit)' was vandalism but the revert 'Revision as of 13:52, April 18, 2007 (edit) (undo)' wasn't that great. Let's try to revert correctly. Thanks. :)MP ^{(talk•contribs)} 20:26, 3 November 2007 (UTC)

Extends indefinitely?

"The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction."

This is contradicted by several observations:

1. Observable space is a finite size, but the Sloan Great Wall had time to form in a Universe that formed 14 billion years ago?

2. Beyond the weakest radiation we see (CMB), it's just dark

3. Hubble redshift

It seems the best way to reconcile all these observations is to suggest that the EM field does NOT in fact stretch across infinity.

It very clearly begins to weaken (Hubble redshift) and weaken (CMB) until it just dies out. —Preceding unsigned comment added by 98.145.87.121 (talk) 16:45, 31 May 2008 (UTC)

New age bullcrap

I hear terms like electromagnetism and electromagnetic fields spewn forth unintelligibly by various individuals subscribing to bizarre spiritual philosophies. Maybe that's worth a mention in a small section of the article, describing perhaps certain colloquial uses of the term? This would of course have to be done by somebody with much less POV than me.

Also, what's with the "skip down to my topic" thing going on at the top of this talk page? Mbarbier (talk) 17:01, 7 June 2008 (UTC)

Distinction between electromagnetic and magnetic field

I added the following text to the introduction:

Note that the field created by a permanent magnet or electromagnet is a magnetic field, not an electromagnetic field; electromagnetic fields are associated with electromagnetic radiation: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. A magnetic field decreases with the cube of the distance from its source; an electromagnetic field decreases more slowly, with the square of the distance, which enables it to propagate for long distances.

It was reverted with the, quite correct, comment:

revert unsourced statement about differentiation between "electromagnetic field" and "magnetic field" -- a magnetic field is a type of electromagnetic field (and is only "purely magnetic" in 1 frame)

Strictly speaking this is correct; however there is a tendency to refer to what is essentially a magnetostatic field, possibly varying, as electromagnetic; I think the article should make the distinction clear in the introduction. Personally I wouldn't be (and wasn't) too concerned about niceties which can be explained in the appropriate part of th body. I'm thinking of statement such as "computer disc drives are subject to erasure by electromagnetic fields". In particular "electromagnetic" is often used inappropriately where electromagnets are involved. It would be useful for anyone who follows a link to this article to have the distinction clearly made in the first screenful. In practice there is a very clear distinction between a ray of light illuminating a tape and a magnet damaging a tape if it is very close (falling off as inverse cube of distance). Pol098 (talk) 00:28, 30 August 2008 (UTC)

The difference between the 2 decreases is due to the field being an entity whose intensity (per unit volume) decreases per the increase in volume, whereas the electromagnetic field is involved with the motion of the volume or (delta volume/delta distance).WFPM (talk) 17:58, 4 March 2012 (UTC)

External links (invisible)

The section "External links" is not visible on display, and I suspect that the problem is related to the reference tags, but I do not know how to correct the problem. -- Wavelength (talk) 02:42, 2 May 2010 (UTC) The categories also are not visible on display, and I mistakenly said in my edit summary that the article had no category. -- Wavelength (talk) 02:59, 2 May 2010 (UTC)]

EMF seems to be an acceptable abbreviation

The lede says that electromagnetic fields are "sometimes incorrectly [called] EMF". However, there's no citation for why EMF is supposedly wrong, and several official sources use the abbrevation EMF, such as:

• World Health Organization
• National Institutes of Health
• National Cancer Institute
• Natural Resources Canada

So I'm going to edit that EMF is an acceptable abbreviation for electromagnetic fields. If I am in error somehow then the article should have an explanation as to why, since reputable bodies are using EMF as an abbreviation. MichaelBluejay (talk) 06:30, 24 May 2010 (UTC)

Any value in providing a DAB hatnote leading to emf? As Old Moonraker, I believe that was the earlier usage. Alternatively, it may be an ENGVAR thing. --Old Moonraker (talk) 17:41, 21 December 2010 (UTC)

Just checked OED: "EMF" links only to "electromotive force". Considering restoring "incorrectly", subject to other editors' views. --Old Moonraker (talk) 17:47, 21 December 2010 (UTC)

Scrub my WP:ENGVAR suggestion: emf as "electromotive force" is the SI system term. --Old Moonraker (talk) 17:56, 21 December 2010 (UTC)

Health and Safety

I'm not entirely certain why the section is labelled as Health and Safety. The body of research on the topic indicates that there is no link between health problems and EM Fields, by and large. I certainly think that it should address things like MRIs. However, it would be more apt to describe it as Public Concern over Health and Safety, then further expanded to describe how all research on the topic, and all reports by major health organizations have found no link between the two.

While the CDC and the WHO have issued precautionary guidelines, they also state no evidence suggesting a connection.

WHO -- http://www.who.int/mediacentre/factsheets/fs304/en/index.html

NIH -- http://www.ncbi.nlm.nih.gov/pubmed/14628308

CDC -- http://www.cdc.gov/niosh/emf2.html

This position is also held by other organizations:

FCC/EPA -- http://www.osha.gov/SLTC/radiofrequencyradiation/epa_990430.html

AEEI -- http://www.aeei.gov.sk.ca/health-effects-and-exposure-guidelines-overview

I could go on, as there is a wealth of data on the topic. The section should be re-formatted as an explanation of the public concern and reasons, versus the wealth of scientific research on the topic, indicating that precautionary guidelines have been issued based on public concerns, not on evidence that there is any evidence suggesting a real health concern.

It should also have an explanation of the nocebo effect's effect on the research.

71.238.163.251 (talk) 05:55, 17 December 2010 (UTC)

Merger proposal -- Flux density

I propose that Flux density be merged into Electromagnetic field. I think that the content in the Flux density article can easily be explained in the context of Electromagnetic field , and the Electromagnetic field article is of a reasonable size in which the merging of Flux density will not cause any problems as far as article size or undue weight is concerned. Do not confuse Flux Density (different capitalization), which already redirects to Electromagnetic field. Chris the speller ^yack 01:13, 15 October 2011 (UTC)

Agree, since the topics are fairly closely tied together and it's not really possible to have flux density as a (relatively) self contained article without a general knowledge of electomagnetic fields.

It would seem odd that the redirect Flux Density redirects here rather than there (to Flux density), that is rather non-intuitive. Suggest listing at RfD to redirect there, but perhaps that might be better to leave until consensus is reached on whether or not to merge. 82.29.185.61 (talk) 16:26, 31 October 2011 (UTC)

Disagree - if flux density can be used for non-EM gravitational fields or general energy flux, it obviously shouldn't be merged with a more narrow article. — Omegatron (talk) 00:45, 21 November 2011 (UTC)

Oppose – As stated by Omegatron. Furthermore, the redirect page Flux Density should be deleted or renamed Electromagnetic flux density. Quondum^talk_contr 04:54, 21 November 2011 (UTC)

Oppose -per Omegatron. Flux density has a mathematical meaning. If anything it should be merged with Flux. — Preceding unsigned comment added by Hypergeek14 (talk • contribs) 10:46, 22 November 2011 (UTC)

Oppose – Merging here is as reasonable as merging "electricty" and "current". Electromagnetic fields and flux density are very different things. - OrbiterSpacethingy (talk) 11:29, 24 January 2012 (UTC)

Disagree - The article Electromagnetic field deals with the classical and quantum treatment of electromagnetic energy viewed as electromagnetic radiation whereas Flux density is flux per unit area, where the flux is either due to existence of electric field or magnetic field. I think it is better to merge Flux density with Flux. Shriram (talk) 15:25, 1 February 2012 (UTC)

Banners removed. See here. F = q(E+v×B) ⇄ ∑_ic_i 17:27, 18 May 2012 (UTC)

Mathematical formalism / undefined quantities and unexplained equations

Hi, I am new here, so maybe I miss something. According to me, the quantities H and D were never introduced in this page, beside the boundary conditions are not clearly explained (what "current free" and "charge free" mean ?). One possibility is to introduce the macroscopic Maxwell's equations (in a medium) in parallel with microscopic ones (in the vacuum). But this will be redundant with the Maxwell's equations page where this job is correctly done. I think this page is aimed to discuss general aspects of Electromagnetism without entering too much in theoretical frames. For instance I have seen that a fluid analogy was discussed as well as health issues. On my side I am working on a Galilean electromagnetism page that is much more consistent then the fluid analogy (but can be somehow linked to it), see Draft:Galilean electromagnetism. The two formalism Galilean and Relativist (Lorentz invariance)can help to disconnected the page from a specific mathematical frame. What do you think ? --Henri BONDAR (talk) 11:15, 4 February 2016 (UTC)

What are the SI units of the electromagnetic field vectors?

In other words is it Newtons per second or what exactly? I am curious. --Ben Houston 03:43, 21 August 2006 (UTC)

[E]=V/m
[B]=T

Cheers --141.33.192.198 15:07, 19 December 2006 (UTC)

si 81.199.168.46 (talk) 08:50, 6 October 2023 (UTC)

EM field generated by a photon?

According to the article, an EM field is generated by moving charges. But doesn’t photon also gives rise to an EM field? —Kri (talk) 14:44, 31 December 2023 (UTC)

No, a photon is a neutral particle and cannot give rise to an EM field. And an EM field is generated by stationary charges. Electromagnetic radiation, eg radio waves, are generated by moving charges.

Photons are quanta, non-classical excitations of a quantum field. Johnjbarton (talk) 02:10, 2 January 2024 (UTC)

You are confusing the electric portion of the electromagnetic field with the whole electromagnetic field. There are good articles in Wikipedia to refresh your knowledge. Bill field pulse (talk) 21:52, 4 January 2024 (UTC)

@Bill field pulse which articles did you have in mind? Johnjbarton (talk) 22:44, 4 January 2024 (UTC)

Electric field and magnetic field for starters. Do you know what a filed is? Bill field pulse (talk) 15:11, 5 January 2024 (UTC)

My knowledge of fields is not relevant. The issues for edits are citations and consensus. I oppose your edits and you have given no sources. Please read Wikipedia:Verifiability and Wikipedia:Citing sources. Johnjbarton (talk) 16:10, 5 January 2024 (UTC)

I do not need to go to sources for obvious things. Using a picture associated with electromagnetic radiation overlooks the reality that attraction occurs all around a charge to an opposite charge without the need for radiation. The picture should state its limitations. Two opposite charges attract. An electric wire with moving electrons involves both kinds of fields. Why show obvious photons and then say there are no photons in classical fields. I will cite sources if we get beyond the obvious. Do you agree that the field itself establishes around a charge at the speed of light in all directions? Or is that not obvious? 67.68.221.81 (talk) 22:17, 5 January 2024 (UTC)

Sorry, I should have logged in that was me. I got a bit excited. Bill field pulse (talk) 22:18, 5 January 2024 (UTC)

"Do you agree that the field itself establishes around a charge at the speed of light in all directions? Or is that not obvious?"

I would say No, it is not true and not obvious. Charge is conserved, so the first question has no meaning. If anything about fields were obvious then we would have needed a couple of centuries of physics and many dedicated scientists to work it out and we would not need college physics courses to explain it. Johnjbarton (talk) 19:23, 9 January 2024 (UTC)

Note it took many centuries to determine the world was round. Today some say it is obvious. A charge is best seen as a EM field source with a location which defines where the field was generated from at a point in time. It only senses the existence of other charges by their field. When one says a hydrogen atom is empty except for 4 tiny charges one ignores that the charges are in constant touch with the other charge's fields. Do you feel a field is rigidly fixed to a charge always there at all distances or does in lag the charge slightly whereby a near light speed charge arrives and the moves out radially from the instantaneous location. If you see it as a fixed entity without lag how do you explain magnetism? Bill field pulse (talk) 19:44, 9 January 2024 (UTC)

Let me explain my thinking further. We know the electromagnetic field around a charge is a physical reality. We know that magnetism cause by moving charges is a property of the field. Except for compressing the field forward how else would charge movement alter a field. The field cannot be immediately all around equally or motion would have no effect. This is the physical reality of why moving charges behave differently the compressed field has greater attraction or repulsion than a non compressed one. I know this is may be considered non obvious if one does not believe a single physical field exists. Bill field pulse (talk) 21:44, 9 January 2024 (UTC)

The speed-of-light dynamics of the EM field is well known to those who study fields and your description immediately above seems reasonable. Your earlier description "establishes around a charge at the speed of light" was my complaint. And none of this is obvious: hence the need for references. I will look for some, but qualitative electro-dyanmics is not easy to find. Johnjbarton (talk) 01:14, 10 January 2024 (UTC)

Yes I see that my wording made it sound like I meant the field moved around the charge. This was unintentional. As I was taught, the fields only go straight out radially in all directions. Sorry.

Can I site you tube stars? They are a prime source of my knowledge. I have a few citations in the works in my sandbox. Bill field pulse (talk) 20:03, 11 January 2024 (UTC)

I deleted "moving".

Resolved

Johnjbarton (talk) 02:11, 2 January 2024 (UTC)

Additionally, a group of photons has an alternating electromagnetic property which does not diminish with distance. Each photon will normally disappear upon encountering an electron capable of absorbing that specific whole photon, sometimes in an appropriate receiver designed for the purpose, like our eyes. Bill field pulse (talk) 16:55, 9 January 2024 (UTC)

Still not related to this article. Johnjbarton (talk) 17:47, 9 January 2024 (UTC)

agreed Bill field pulse (talk) 19:06, 9 January 2024 (UTC)

I deleted material related to quantum mechanics.

As far as I can tell, the purpose of this article is to discuss classical electromagnetic fields. In any case it makes no sense to mix up quantum and classical in the way that was done. So I just cut out the quantum parts I could find. Johnjbarton (talk) 02:13, 2 January 2024 (UTC)

@Bill field pulse This is also an explanation for a few reverts I did before I realized the extent of the confusion on this page. Johnjbarton (talk) 02:25, 2 January 2024 (UTC)

Here is the confusion; An electromagnetic field reaches out around a proton in all directions. If the proton moves the field must have a magnetic component. As well the field reestablishes radially outward at the speed of light. This is how a proton holds an electron no mater where it goes. The attraction between an electron and a proton is not instantaneous at any distance the electron goes to. Yes electromagnetic radiation also moves out at the speed of light but only when the oscillations are enough to produce photons. Electrons are not held to nuclei by photons moving in a single direction they are held by a 3 dimensional field. The field is a physical change to space. It is not action at a distance. Only local action here. Bill field pulse (talk) 22:34, 5 January 2024 (UTC)

If any of this is not obvious to you be very specific which single thing is not obvious and I will provide a source, Bill field pulse (talk) 22:37, 5 January 2024 (UTC)

I want to be very specific: whenever you add content, add a source. Johnjbarton (talk) 00:44, 6 January 2024 (UTC)

Interference and Health and Safety sections.

I think the sections "Interference" and "Health and Safety" are issues for Electromagnetic radiation. Of course radio waves are time varying EM fields, but I would not expect to see these topics in a textbook discussion of EM fields until the issue of EM radiation is considered. Johnjbarton (talk) 22:15, 6 January 2024 (UTC)

Yes, it's odd to have that here, and particularly to jump into technical-manual details the way it does. XOR'easter (talk) 23:10, 6 January 2024 (UTC)

While I'm not a fan of splitting articles generally, the two topics, "what does science mean by electromagnetic field" and "effects of electromagnetic radiation" seem to target quite different audiences. Even moving this to electromagnetic radiation would not solve that aspect. Maybe Effects of electromagnetic radiation? Johnjbarton (talk) 00:58, 7 January 2024 (UTC)

The section on Interference was only about DSL it turns out. So I WP:BOLDly moved the content to Digital telephone electrical interference (which I created by moving a tiny article for one of the kinds of noise. Johnjbarton (talk) 01:22, 8 January 2024 (UTC)

The proper merge target for the Health and Safety appears to Electromagnetic radiation and health. Johnjbarton (talk) 01:24, 8 January 2024 (UTC)

good idea you could put a link to those articles Bill field pulse (talk) 20:13, 8 January 2024 (UTC)

"Feedback loop" section

What's the point of it? Why is the article devoting so much space to a peculiar way of describing one aspect of electromagnetism in awkward bullet-point form? It's like a fragment of 2002 Wikipedia that nobody bothered to remove. XOR'easter (talk) 23:53, 6 January 2024 (UTC)

There are important two "loop" concepts buried in the section: 1) charges both create and are affected by the fields, 2) the alternation or reciprocal generation of the electric and magnetic components in wave propagation. These seem mixed and some other stuff thrown in the hopper as well. The entire middle paragraph seems to be about another topic, conduction vs free space charge acceleration.

I think these 3 are all good topics to cover but the current text is not the way to do so. Johnjbarton (talk) 01:06, 7 January 2024 (UTC)

I think the whole Feedback Loop section needs to go. And the Interference section is awkward and long. Dilaton (talk) 20:48, 7 January 2024 (UTC)

Both have been removed now. XOR'easter (talk) 02:05, 8 January 2024 (UTC)

agreed Bill field pulse (talk) 19:46, 8 January 2024 (UTC)

Structure section.

I think the entire content of the Structure section and the figure should be removed in favor of a section on static field structure, eg Faraday iron filings like view. Johnjbarton (talk) 23:03, 7 January 2024 (UTC)

I've carved out a section where iron filings and such can go. XOR'easter (talk) 02:33, 8 January 2024 (UTC)

Great, I think the remaining issue is what is the goal for the article. To me it should be: summary articles linking other pages. It is close to that goal. Johnjbarton (talk) 02:36, 8 January 2024 (UTC)

I despair of finding a good way to organize all this, but that might not be a bad one. XOR'easter (talk) 02:42, 8 January 2024 (UTC)

It is already much better Bill field pulse (talk) 19:47, 8 January 2024 (UTC)

Just show two charges moving parallel in space, one ahead of the other. The EM field ahead of each charge is compressed; and the field behind each charges is stretched. The leading charge curves outward a purely magnetic effect. The following charge curves INWARD into the thinned field behind the other charge also a purely magnetic effect. Both charges also accelerate apart electrically along the axis between them. I trust this is obvious and not original thought. Bill field pulse (talk) 20:55, 8 January 2024 (UTC)

There may be a drawing showing this on you tube. Bill field pulse (talk) 21:11, 8 January 2024 (UTC)

So many other articles.

(I should have learned by now).

We have Electrostatics and electric field and electromagnetic radiation and Classical electromagnetism.

Seems to me this article needs to be merged with one of the above. Or maybe converted into "Effects of electromagnetic radiation". Johnjbarton (talk) 23:08, 7 January 2024 (UTC)

Absolutely wrong. Merging them would be foolish Bill field pulse (talk) 19:48, 8 January 2024 (UTC)

No offense intended, The article is already much improved as a source of information. Bill field pulse (talk) 20:04, 8 January 2024 (UTC)

Just put links to other articles. Even add text see also .... for more about.... Bill field pulse (talk) 20:15, 8 January 2024 (UTC)

"Because of the interrelationship between the fields"

The intro has this sentence:

• Because of the interrelationship between the fields, a disturbance in the electric field can create a disturbance in the magnetic field which in turn affects the electric field, leading to an oscillation that propagates through space, known as an electromagnetic wave.

It ends with a reference supporting this claim.

The reference has an image including an antenna. I think the problem here is that only way to change the electric field is to move charges which create magnetic fields. The electric/magnetic field split is artificial there is only a solution to the field equations, not two things. So we can say they generate each other or we can say they are both generated by moving charges, but we can't decide because no physical experiment can distinguish these points of view. (I don't have a ref however).

@Bill field pulse Do you have a reference for your point of view? Johnjbarton (talk) 19:32, 8 January 2024 (UTC)

Look down at the section whereby one observer sees a magnetic field and another moving with the charge sees only an electric field. If there is only one actual underlying field how can one happen before or after the other. They produce the very same force on a charge in space time thou the force may appear different to different observers Bill field pulse (talk) 19:56, 8 January 2024 (UTC)

The use of "can create" and "in turn" is bad because they are the very same effect produced by the same charge. Bill field pulse (talk) 20:08, 8 January 2024 (UTC)

A changing electric field creates magnetic circulation; a changing electric field creates magnetic circulation. Saying anything else in the intro overcomplicates matters, at best. At worst, it would be bringing in special relativity in order to try and avoid the plain implications of Maxwell's equations, which makes no logical sense. XOR'easter (talk) 20:10, 8 January 2024 (UTC)

A changing electric field does not "create" magnetic circulation. They are both evidence of some underlying charge behavior. When a wire shows magnetism the electrical fields of all still there: protons(Quarks) and the electrons are still there they are just balanced (neutral) so that only the magnetic effect is visible. Bill field pulse (talk) 20:22, 8 January 2024 (UTC)

Bringing in quarks is a distraction when the point is to explain the content of classical electromagnetism, particularly Maxwell's equations. XOR'easter (talk) 20:25, 8 January 2024 (UTC)

Absolutely lets not bring in relativity. Other explanations would be original research. However, we can use Maxwell's equations which are equalities. The changing current equals the magnetic effect. There is no before and after unless there is distance involved and speed of light needs to be considered. We can say they are simultaneous without issue because they are at the same place in space and time. Bill field pulse (talk) 20:39, 8 January 2024 (UTC)

Saying that the changing electric field can't be seen as the cause of magnetic circulation would itself be original research. XOR'easter (talk) 20:57, 8 January 2024 (UTC)

Please cite exactly where "create" was used and just go with that. Bill field pulse (talk) 21:02, 8 January 2024 (UTC)

Even Einstein made mistakes "create" was probably a mistake of some smart person Bill field pulse (talk) 21:03, 8 January 2024 (UTC)

As noted at the beginning of this section, we already had a reference saying that. XOR'easter (talk) 21:13, 8 January 2024 (UTC)

Okay I think it is wrong but it appears that is original thought. Thanks for discussing it anyway. Bill field pulse (talk) 21:17, 8 January 2024 (UTC)

Reference style

I had very deliberately used {{sfn}}'s for the references to Purcell–Morin and to Feynman–Leighton–Sands, because both were being cited multiple times for different pages, and {{rp}} would make for a lot of cluttered superscripts in the main text. Now Purcell–Morin is being cited with {{rp}} and Feynman–Leighton–Sands is being cited with {{sfn}}. Can we settle on a single way to do it so that this doesn't happen? XOR'easter (talk) 18:38, 12 January 2024 (UTC)

Incidentally, the creator of {{rp}} says that it is obsolete. XOR'easter (talk) 18:48, 12 January 2024 (UTC)

Ok I was just trying to get to one or the other. The majority seemed be the ref style. I wouldn't have changed otherwise.

(I think the rp clutter cuts both ways: yes it is kinda noisy, but it also makes the pages clear, the reference mouse over gives the source directly, and it tells a reader that an editor took some effort to identify the spot in the text.) Johnjbarton (talk) 19:13, 12 January 2024 (UTC)

Using ref tags for sources cited once and {{sfn}}s for sources with different pages cited in different cases is considered a consistent "citation style". It has the advantage of not throwing too many page numbers into the main text, while also making it easy to add one-off references in the Visual Editor. I'm not nearly as {{rp}}-hostile as some editors; the way it is now seems fine, except that somewhere we lost the links to the individual sections of the online Feynman Lectures, which were convenient. XOR'easter (talk) 19:25, 12 January 2024 (UTC)

Ok news to me. It does not look consistent to readers; to me the mix looks like hodge-podge.

The SMcCandlish you pointed to suggests ref= in ref tags. Seems largely the same as sfn but using only ref tags. I've asked for an update on User_talk:SMcCandlish Johnjbarton (talk) 19:39, 12 January 2024 (UTC)

OK, after SMcCandlish's edit, I went back and added the URLs to the individual Feynman Lectures sections. Caltech took the trouble to put them online, so we might as well take advantage of that. XOR'easter (talk) 00:34, 13 January 2024 (UTC)

Hope the conversion I did is agreeable. :-) After doing a couple of these to memorize the parameters and stuff, it gets robotically easy.  — SMcCandlish ☏ ¢ 😼  00:38, 13 January 2024 (UTC)

I like the {{sfnp}} style as well. It also allows distinguishing between a specific page(s) meant in a citation (in the sfn) and the range of pages that the reference occupies (in the full citation). The current mix of {{sfnp}} and <ref>...</ref> is not too bad – sometimes a footnote pops up two levels (a harvard-style ref and then a full ref) and others just one level (a full ref). The reference section ends up as a mix of short and full, followed by a separate list of full refs. Does anyone object if I migrate the full refs to {{sfnp}} as well? —Quondum 13:58, 13 January 2024 (UTC)

I don't think it's necessary, but I don't have any objection if you want to take the time to do it. XOR'easter (talk) 20:37, 13 January 2024 (UTC)

According to Wikipedia:Citing_sources#Citing_multiple_pages_of_the_same_source the rp template is still a recommended solution. sfnp is not even mentioned. Johnjbarton (talk) 17:14, 14 January 2024 (UTC)

{{sfn}} is, higher up, at WP:SFN. The section that you refer to should be updated. It is referenced as the "Short citations" bullet. There are several variants of sfn and harv, so will not all be listed. —Quondum 18:00, 14 January 2024 (UTC)