Talk:Force between magnets

Treatments of the magnetic dipole field

I have started a general discussion of the many treatments of the magnetic dipole field at Wikipedia talk:WikiProject Physics#Treatments of the magnetic dipole field. RockMagnetist (talk) 03:10, 3 August 2011 (UTC)[reply]

Force equation between two dipoles is wrong.

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}))]

http://downloads.hindawi.com/archive/1998/079537.pdf — Preceding unsigned comment added by Ze-aksent (talk • contribs) 04:48, 23 November 2012 (UTC)[reply]

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) 23:09, 19 November 2012 (UTC)[reply]

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The source referenced from where the formula for "Force between two magnetic poles" is taken gives the title "Coulomb's Law". Is there a Coulomb's Law also for magnetism ? If so it is not reported here Coulomb's law . Or is it a mistake of the source and the formula is not valid ? 95.244.59.30 (talk) 18:34, 22 May 2023 (UTC)[reply]

equations for the cylindrical magnet are inconsistent with the bar-magnets

It seems like some of the equations of the Gilbert model for the force between cylindrical magnets are inconsistent with those for the bar-magnets. Starting from the latter the first equation for the cylindrical magnets seems to be missing the term (h²+R²)/h². In addition, I think the following equation should be B_0=mu_0*M/2, as that was the relation given in the bar magnet section, and used to derive the force between cylindrical magnets. Could someone double-check this? And either fix the equations or add an explanation in the article explaining why is should not be as I said here, to avoid confusion.) 81.241.27.157 (talk) 08:40, 13 January 2017 (UTC) Danny[reply]

==I am glad I was not the only one to notice: The equation in "Force between two cylindrical magnets" seems to be missing the "L" factor of the previous equation in "Force between two bar magnets" in the first part, while in the second is simply replaced by "h" factor". The first part doesn't make sense (unless L = R), or simply doesn't make sense! 2A02:587:4508:2C00:688F:C34C:D0FC:9449 (talk) 23:17, 23 July 2017 (UTC)[reply]

Small note:

About the phrase " The direction of the magnetic dipole moment points from the negative south pole to the positive north pole of this tiny magnet.". It seems logical from first view that this should be the other way round, since the conventional direction of current is opposite. Someone should take a minute to explain this INSIDE the article. — Preceding unsigned comment added by 2A02:587:4508:2C00:688F:C34C:D0FC:9449 (talk) 19:18, 23 July 2017 (UTC)[reply]

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Force on pole in field?

What's the force on a magnetic pole q in a magnetic field of strength B? Mollwollfumble (talk) 13:23, 19 November 2017 (UTC)[reply]

Origin of the term "Gilbert model"

The article makes heavy use of the term "Gilbert model" for the description in terms of magnetic poles. I wonder where this term originates from, and how established it is. Can we at least quote an influential source? --Geek3 (talk) 14:43, 16 January 2019 (UTC)[reply]

It seems to originate with one author and should probably be dropped. See Talk:Magnetic field#Magnetic pole model confuses. RockMagnetist(talk) 17:31, 16 January 2019 (UTC)[reply]

The Gilbert model still is still taught and is confusing. I remember a long fruitless discussion on the German Wiki. I think it is ok to mention it here. Anyway, would be good to change the positons of the Ampere and Gilbert sketches on the right to show them in the right timeline. HolgerFiedler (talk) 06:26, 21 November 2020 (UTC)[reply]

I don't know about Germany, but in the English literature the only source for the term is "Introduction to Electrodynamics" by Griffiths. It is just his name for a particular way of solving the boundary value problem for the magnetic field, not a model at all. I have discussed it extensively at Talk:Magnetic field. The consensus on that page was to drop any reference to the term, and that is what I think should be done here. RockMagnetist(talk) 18:00, 30 November 2020 (UTC)[reply]

For now, I replaced the term 'Gilbert model' with 'Magnetic-charge model'. If you come up with a better term, this may be replaced again in future. --Geek3 (talk) 16:25, 3 February 2021 (UTC)[reply]