Talk:Electromagnetic field

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Science

Electric and magnetic field 112.198.193.121 (talk) 13:47, 11 November 2023 (UTC)[reply]

Please see also BASIC IDEA CLARIFICATION REQUEST topic below thanks. Bill field pulse (talk) 22:10, 23 January 2024 (UTC)[reply]

"In alternating current the electromagnetic field ..."

@Bill field pulse I've removed a paragraph you added recently.

I believe the paragraph mixes up two different concepts: alternating current and the relation between E and B fields. It's possible that your explanation relates these two concepts, but I can't make out how and I can't verify it because the paragraph has no references. To be honest I think what ever you are trying to get across is too complex for this article.

I gather from this and other edits that you are especially keen to get across that electric fields don't cause magnetic fields directly and vice versa. I've made several edits in the article to reduce the chance that readers will come away with this mythological concept. In particular I added a paragraph at the end of "Time-varying EM fields in Maxwell’s equations".

However, the concept is generally fine as a guide in small systems because the changes in EM fields cause charge rearrangement at the speed of light. I think that is the reason that it is hard to find references: the E causes B causes E could be considered an approximate model that words very well.

What we really need are good references. Johnjbarton (talk) 17:20, 12 January 2024 (UTC)[reply]

Regarding references, please note that [Purcell's Electricity and Magnetism] is available online and covers all of the material that I expect we would want in this article. Johnjbarton (talk) 17:29, 12 January 2024 (UTC)[reply]

"We also know what happens when the electric and magnetic fields are disturbed. A disturbance in an electric field disturbs the magnetic field which in turn disturbs the electric field again; energy sloshes back and forth between the two fields, and the whole disturbance propagates along at a speed which is one of the fundamental constants of nature." — David Goodstein [1]

Like all statements that use words instead of equations, it's a heuristic, but it's a darn good one, and not something we can say is wrong without sources explicitly saying that a statement all over the undergrad curriculum is actually wrong. (That can happen; it's not impossible.) I don't think it's "hard to find references" because they focus on small systems; I think the references generally don't talk about charge motion because they are concerned with the propagation of waves through volumes of empty space. XOR'easter (talk) 17:52, 12 January 2024 (UTC)[reply]

I was thinking of rewriting the whole transformation of fields section to follow the example that Purcell uses, of a laboratory containing a current-carrying wire and a test charge in motion parallel to the current. XOR'easter (talk) 17:56, 12 January 2024 (UTC)[reply]

I was not sure how to highlight an issue to you..... There seems to be a group of people who see electromagnetic field and electromagnetic radiation interchangeably especially in the quantization of EM article. The two differ as follows: Confusion between electromagnetic field and electromagnetic radiation. Today many people use electromagnetic radiation and electromagnetic field interchangeably even though they are entirely different phenomena. It is very hard for me to imagine how this confusion exists. One involves the transfer of energy and can travel huge distances undiminished the other follows coulombs law and looses strength according to one over distance squared. One is continuous and exists around charges in 3 dimensions no matter how the charges move. The other forms only perpendicular to an oscillating charge. One holds the electron to the proton and the reverse. The other is produced when the electron sheds energy suddenly. One applies to all charges and needs to be revisited based upon how quarks move the other is a well studied phenomenon and is entirely due to electrons dropping energy levels. Bill field pulse (talk) 22:19, 18 January 2024 (UTC)[reply]

If this article is confusing, this is the place to discuss it. However, it is not Wikipedia's purpose to take on other people's confusion. See WP:RIGHTGREATWRONGS. Constant314 (talk) 01:09, 19 January 2024 (UTC)[reply]

Wikipedia should not treat em field and em radiation as being the same. Especially in quantization of em field article. Seems like Wiki is the confused entity. Consensus Cheat (talk) 13:49, 20 January 2024 (UTC)[reply]

The place to discuss that is on the talk page of the Quantization of the electromagnetic field article. Constant314 (talk) 13:52, 20 January 2024 (UTC)[reply]

Thanks Bill field pulse (talk) 16:25, 20 January 2024 (UTC)[reply]

If you are looking for suggestions on how to "highlight" an issue I have two:

Be specific. Rather than broad discussions about groups of people complain about specific paragraphs in the article.
Discuss references. Your opinion is not more useful than "groups of people", but your verifiable reference will be be consulted.

This article provides an overview of classic static and dynamic EM fields. As such it has no concern for electrons and protons or for quantization. Johnjbarton (talk) 02:23, 19 January 2024 (UTC)[reply]

Okay with me if you don't think it helps the article. I thought it was a good example of how with an alternating current there is usually very little electromagnetic radiation and the EM field can be pure electric, pure magnetic and all cases in between without any need for frame of reference changes.

When you say charge rearrangement at "the speed of light" I think you mean "very close to the speed of light". Bill field pulse (talk) 19:57, 12 January 2024 (UTC)[reply]

Basic Idea Clarification requested please.

Do we all agree on the basic concept that the EM Field is said to to be a physical reality that allows distant charges to interact without the need to touch? Really, please confirm we are all on the same page.

I.e. each charge is the center of an EM field it creates.

Otherwise I would like to hear how others think two static charges repel when there is no radiation between them.

If you believe in non local interaction please say so. i.e. instantaneous action at a distance. Bill field pulse (talk) 22:07, 23 January 2024 (UTC)[reply]

Quotes

Richard Feynman The Vector Potential. In section 15-4,

"A real field is a mathematical function we use for avoiding the idea of action at a distance."
"A “real” field is then a set of numbers we specify in such a way that what happens at a point depends only on the numbers at that point."

Comment: Feynman does not say that a real field is something that can be represented by numbers. He says that a real field is numbers.

John David Jackson ^[1]^: 28

"It [the electric field] is a vector function of position, denoted by E."

Comment: A vector function is just an ordered set of numbers. This is all Jackson says.

Edward M. Purcell ^[2]^: 16

"Is it [the electric field] something real or is it merely a name for a factor in an equation ... since it works, it doesn't make any difference."

Comment: You can assume that the electric field is something real and I can assume that it is nothing but numbers attached to points in space, and we will both get the right answer. If you assume that the field acts in anyway different from numbers attached to points in space, you will get a wrong answer.

David J. Griffiths ^[3]^: 61

"I encourage you to think of the field as a real physical entity ... I can't tell you, then, what a real field is -- only how to calculate it and what it can do for you once you've got it."

Comment: Griffiths likes to think of the field as physical. Many people also think that. But he is not going to tell you that it is physical, because he cannot. He cannot give you any reason to believe that the field is anything other than numbers attached to points in space. But notice the words he uses. He can tell you what the numbers that you calculate can be used for, but he does not say that he can tell you what the field does. Numbers cannot do anything. If Griffiths could tell you anything that the field does, that numbers attached to points in space cannot do, then he would have evidence of the field being physical.

Whether the field is physical or not, everybody agrees that the field has no mechanical properties. It doesn't compress, expand, wave, wiggle, jiggle, move, or stick to things.. You cannot have a linear velocity with respect to the field, just like you cannot have a linear velocity with respect to space. Constant314 (talk) 23:30, 23 January 2024 (UTC)[reply]

Not you too. However you interpret the texts you cited, your conclusion "everybody agrees that the field has no mechanical properties" is invalid. There is no field that does not fit the description, so your argument would allow us to conclude that reality has no mechanical properties. Now: both of you, desist. This is not the place for unreferenced debates, nor is it the place for synthesizing interpretations based on wording in texts. —Quondum 23:52, 23 January 2024 (UTC)[reply]

I object me and Constant314 see things differently, if not here where do we reach some kind of common ground. certainly not in the article. Do you agree too much EM Radiation in the EM field article? Also No talk of quantum of charge in the Quantization of EM Field article. It is quantized because when you look at smaller and smaller fields the particles begin to become apparent (Electrons and quarks not mini particles still sought after) right? Bill field pulse (talk) 21:57, 24 January 2024 (UTC)[reply]

Constant314 You are right there are different opinions Feynman was a particle guy who liked gluons. I must agree with Quondum here. When I say physical reality I mean it. The charge is little more than the origin the field. A charge only interact with the fields of others. I do not believe in a bunch of mini particles much smaller than electrons and quarks make a pseudo field effect. I believe a gluon is a lazy way out, rather than figuring out how a compressed EM field causes a extreme magnetic like attraction. Bill field pulse (talk) 21:52, 24 January 2024 (UTC)[reply]

References

^ Jackson, John David (1975), Classical Electrodynamics (2nd ed.), John-Wiley, ISBN 047143132X
^ Purcell, Edward M. (1963), Electricity and magnetism (1st ed.), McGraw-Hill, LCCN 64-66016
^ Griffiths, David (2012), Introduction to Electrodynamics, PHI Learning Private Limited (Indian Reprint), ISBN 9788120316010

This article gives an overview...

Some time ago I added this sentence to the intro:

This article gives an overview of the classical electromagnetic field and introduces many related articles with more details.

It was removed by @Fgnievinski with the edit summary

see MOS:SELFREF;

At first I thought this was a correct MOS thing, but then I read the referenced page more carefully. See MOS:SELFREF. That page says explicitly:

This means that while articles may refer to themselves, they should not refer to "Wikipedia" or to the Wikipedia project as a whole (e.g. "this website").

And the side give an example with a green check for "This article discusses..."

Based on my reading I want to return this paragraph to the intro.

Is it correct, the article is an overview,
It sets expectations for readers that they may need to dig into linked article to get details,
It encourages readers to scan knowing they won't be burrow down so much as flying over,
It encourages editors to keep to a summary style here and move to linked articles for significant addtions.

Johnjbarton (talk) 22:10, 24 March 2024 (UTC)[reply]

Normally, a hatnote is the proper way for warning the reader this page might not be what they are looking for. If this were an introductory article, it could be tagged with Template:Introductory article; but then, what would be the corresponding non-introductory article about EMF? The problem with the disclaimer at hand it's a vacuous truth for readers: of course other articles will give more details about other topics. If there are notable omissions, it's better to leave a hidden comment in the article source or start a to-do list in the talk page. If the goal is to alert editors to adhere to summary style, the best way is to use an editnotice, which is displayed when editing a page (try editing Sport, for example). Based on the motivation described in your edit summary, I've now taken the liberty of requesting the editnotice: Template talk:Editnotices/Page/Electromagnetic field. fgnievinski (talk) 03:35, 25 March 2024 (UTC)[reply]

Summary style is exactly what I meant; thanks for the editnotice. Johnjbarton (talk) 14:53, 25 March 2024 (UTC)[reply]

Hello. I understand your intention. I agree that I did not see a MOS violation. I think it is more in the spirit of the no disclaimers guidelines. The reader simply does not need to be warned that the article is an overview. That is practically the default for an encyclopedia. But to speak to your points:

1. No, it is the usual mishmash of shallow and deep discussion.
2. That should be the default expectation.
3. The typical reader won't have a clue about the distinction between an overview and something else.
4. Please don't be offended, but LOL! WP editors won't give that encouragement even a second thought.

Constant314 (talk) 04:06, 25 March 2024 (UTC)[reply]

[Jackson_2-1] Jackson, John David (1975), Classical Electrodynamics (2nd ed.), John-Wiley, ISBN 047143132X

[Purcell_1963-2] Purcell, Edward M. (1963), Electricity and magnetism (1st ed.), McGraw-Hill, LCCN 64-66016

[Griffiths_2012-3] Griffiths, David (2012), Introduction to Electrodynamics, PHI Learning Private Limited (Indian Reprint), ISBN 9788120316010

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