Talk:Magnetic moment
From Wikipedia, the free encyclopedia
 |
This article is within the scope of WikiProject Physics, which collaborates on articles related to physics. | |
| ??? | This article has not yet received a rating on the assessment scale. [FAQ] | |
| ??? | This article has not yet received an importance rating within physics. | |
|
Please rate this article, and then leave comments here to explain the ratings and/or to identify the strengths and weaknesses of the article. |
||
Contents |
[edit] Cleanup required
I've marked this article for cleanup, due to its confusing and sometime incorrect explanations (see "Current, not poles" below). For a much better discussion of magnetic dipoles and magnetism, see magnetism.
ALSO The magnetic moment discussion here makes no mention to the magnetic moment in chemistry, only in physics. Can this hopefully be updated to include this information?
[edit] Current, not poles
The explanation of a magnetic dipole moment as being created by two poles separated by some distance is incorrect. This is true for electric dipole moments, but magnetic dipole moments are created by current loops, or by the aggregate effect of many intrinsic dipole moments, such as by many electrons whose spins are aligned, as in a bar magnet.
Magnetic monopoles, such as those implied in the discussion here, have never been detected, although there remains some possibility that they do exist. Even if they do, however, it is extremely unlikely that they are responsible for magnetism in the everyday sense.
[edit] Molecular Dipoles
The page mentions the dipoles of electrons and nuclei, but molecules themselves have a dipole. It is of great importance in the field of chemical solvents and their respective miscibilities. This should be added.
[edit] unclear phrase
the phrase
Any rotating charged object has magnetic moment from the earth to the electron.
is quite cryptic. Can anyone elaborate or rephrase? ~~
Better rephrasing would be: "Any rotating charged object (from as large as the earth to as small as electron) has magnetic moment"
This is also untrue. A uncharged rotating object will have no magnetic dipole moment.
I'm not sure what people are saying here. The earth has zero net electric charge, yet it does have a magnetic dipole moment (due to currents in the core, most likely). The electron is charged, and it has a magnetic dipole moment, but is it rotating? Hard to say; it has "spin", but that's an internal quantum number, and it's a point particle. The neutron is uncharged, but it does have a magnetic dipole moment. HEL 18:47, 5 November 2006 (UTC)
[edit] Vectors vs scalars
Am I right that in the equation mew = I A the current I is a scaler? If it is, that should be noted.
[edit] Start simple, then work up
While a novice reader will easily understand the definition in terms of a permanent magnet, the "magnetic moment in a magnetic field" will throw them very early in the article. It is good to keep the explanations/usages of the term itemized and summarized at the top of the article, but phrases should be added to distinguish them as different definitions (not in meaning, but in explanatory mechanism.) The separate paragraphs don't quite achieve this on their own.
Moreover, this lumping of a simple bar magnet in with a more complex relationship between magnet and another body/field continues in the "Explanation" section. It might be best to explain the stand-alone bar magnet longhand, e.g. give a few examples of a short powerful magnet and a big weak one. This may sound braindead, but it will help build confidence in the reader and encourage them to try to understand the next section, which would hopefully also be made more explicit. (71.233.165.69 01:49, 10 June 2006 (UTC))
[edit] A is a bad vector name
A is commonly used as the magnetic vector potential, and "a" as the surface normal vector.
[edit] Magnetic quadrupole moment and higher?
This page seems to equate "magnetic moment" with "magnetic dipole moment". This is wrong since there are magnetic quadrupole, octupole, ... moments as well. Either the page should be renamed "Magnetic dipole moment", or it should be changed to state "the most commonly encountered type of magnetic moment is the magnetic dipole moment" and then also mention the quadrupole, etc. HEL 18:50, 5 November 2006 (UTC)
[edit] Changes made
I'm a Physics-Major and currently enrolled in a course on Electricity and Magnetism, I am in the process of editing some of this page. I have changed the definition of the magnetic dipole at the top of the page to its correct definition.
[edit] phrase
This: (Curl your fingers in the direction of the current, your thumb will point in the direction a). sounds funky. Am I wrong in saying that you cannot curl your fingers in the direction of current (in a wire)? How do you curl fingers around the direction of a straight-moving thing? You curl your fingers around a conductor/wire in the direction of the magnetic lines of flux and then your thumb should be pointing in the direction of the current... or at least, that's what I was taught (and the old-timers with their "conventional current" will use a "left-hand rule"). However, I could have this all wrong/misunderstanding the author's meaning. Gaviidae 15:46, 2 March 2007 (UTC)
