Talk:Magnetic dipole

Physics Start‑class Mid‑importance

	Physics portal This article is within the scope of WikiProject Physics, a collaborative effort to improve the coverage of Physics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.PhysicsWikipedia:WikiProject PhysicsTemplate:WikiProject Physicsphysics articles
Start	This article has been rated as Start-class on Wikipedia's content assessment scale.
Mid	This article has been rated as Mid-importance on the project's importance scale.

Back to being an article

This page was changed from a redirect to an article following a discussion of a need for such a page at Wikipedia talk:WikiProject Physics#Treatments of the magnetic dipole field. RockMagnetist (talk) 01:24, 8 August 2011 (UTC)[reply]

Review as requested by RockMagnetist

RockMagnetist asked what I felt about this article on talk:magnetic field. This is my reponse. First, I like the overall approach for this article, despite the fact that in physics at least it is a little non-standard. It does assume a certain level of sophistication (Calc III and junior level E&M) on the part of the reader. I don't see a reason for a non-technical reader to have much interest in this article, though. I also like the way it comes straight to the point and is parsimonious with words. This article does not need too much work. My main criticism is that I think it jumps too quickly to the magnetic potentials without sufficiently, IMO, motivating how the magnetic moment relates to the magnetic potentials. For that reason, I recommend adding two more sections: a short qualitative description section of the two models of the magnetic moment and a section on the potentials perhaps showing the Poisson's equations that lead to the solutions of A and φ used in the first section of the current article. Good work. TStein (talk) 20:10, 25 November 2011 (UTC)[reply]

Thanks for the suggestions, TStein. RockMagnetist (talk) 01:50, 26 November 2011 (UTC)[reply]

It's like, if you can understand the lede then you don't need to be reading this. The rest of us are thinking - huh!? Richard Avery (talk) 14:22, 19 January 2013 (UTC)[reply]

I have copied much of the technical stuff of this article over to magnetic moment and I am thinking about changing the focus of this article to be a qualitative description of the magnetic dipole with appropriate links to the more technical details on other articles. Does anyone have any thoughts on that? TStein (talk) 21:48, 31 May 2018 (UTC)[reply]

Force equation between two dipoles is wrong

It should go like this:

{\vec {F}}_{ab}={\frac {3\mu _{0}}{4\pi |r|^{4}}}[({\hat {r}}\times {\vec {m}}_{a})\times {\vec {m}}_{b}+({\hat {r}}\times {\vec {m}}_{b})\times {\vec {m}}_{a}-2{\hat {r}}({\vec {m}}_{a}\cdot {\vec {m}}_{b})+5{\hat {r}}(({\hat {r}}\times {\vec {m}}_{a})\cdot ({\hat {r}}\times {\vec {m}}_{b}))]

where ${\hat {r}}$ is unit vector pointing from magnetic moment $m_{a}$ to $m_{b}$ , and $|r|$ is the distance between those two magnetic dipole moments. — Preceding unsigned comment added by Ze-aksent (talk • contribs) 23:08, 19 November 2012 (UTC)[reply]

Do you have a citation for that? The existing equation does. RockMagnetist (talk) 23:24, 19 November 2012 (UTC)[reply]

Here: http://downloads.hindawi.com/archive/1998/079537.pdf

These guys say they were the fist ones to derive it, in 1998. They used vector differential and path integral derivation and arrived to the same equation. Ze-aksent (talk) 04:44, 23 November 2012 (UTC)[reply]

By the way, the existing citation links to document where the relevant page 140 is no available. — Preceding unsigned comment added by Ze-aksent (talk • contribs) 06:49, 23 November 2012 (UTC)[reply]

Both expressions are correct. You can get from this expression to the one in the article using the triple product expansion. RockMagnetist (talk) 18:47, 23 November 2012 (UTC)[reply]

Can you show me? -- And do you have citation for that equation in the article? Current reference is missing the page where that equation supposedly came from. Do you have some actual reference?

Ze-aksent (talk) 04:54, 24 November 2012 (UTC)[reply]

We're discussing this in two places. Let's have one conversation at Talk:Magnetic moment. RockMagnetist (talk) 05:23, 24 November 2012 (UTC)[reply]

Ok, just please give me some actual reference to that equation in the article.

Ze-aksent (talk) 10:06, 24 November 2012 (UTC)[reply]

Bad URL (?)

The URL for "Permanent Magnet and Electromechanical Devices: Materials, Analysis, and Applications" is http://books.google.com/?id=irsdLnC5SrsC&dq=permanent+magnet+and+electromechanical+devices&printsec=frontcover&q=3.130.

The q= causes the Google book to search for 3.130, which seems to me wrong. — Preceding unsigned comment added by 2601:18F:800:C4A1:9D8A:58CB:33FA:F9CE (talk) 17:23, 30 July 2016 (UTC)[reply]

Thanks for pointing this out. Normally, we shouldn't include a url for a Google Books search result, but this might be an exception. The source is being used for a particular equation which is in fact equation 3.130 in that book, and since it's a snippet view it's hard to see how else the equation could be viewed. However, I think it would be less confusing if I moved this reference out of References and into the citation. RockMagnetist(talk) 18:07, 30 July 2016 (UTC)[reply]

Field formula is wrong

Both parts of the field should vary with radius as 1/r^3 (e.g., Jackson eq. 5.56) David s graff (talk) 20:17, 16 March 2017 (UTC)[reply]

I presume you're referring to the first term in the second equation. The symbol

\mathbf {r}

refers to the full vector, not a unit vector, so the numerator is proportional to r^2. RockMagnetist(talk) 15:25, 17 March 2017 (UTC)[reply]