Talk:Electric dipole moment

Archived talk from Talk:Electrical dipole moment

I clarified the meaning of r in the generic discrete case as before it was not distinguished from the r of the simple case and added a link to Vector (spatial for further reading (this is an introductory enough article to warrant a link to another introductory topic?). Still, the generic definition does not deal with $q_{i}$ of all the same charge.....

Also, what is going on with the definition of a generic distribution? We have q- --> q+ for r(vector), but the generalization does not specify what happens if we have multiple q+ in our set of charges. Is this r(vector) in the general case taken to be a vector from some origin?

Could somebody explain the significance. I don't understand the maths here either as electrial fields obey the inverse square law so I would expect the moment to decrease wrt this principle.Rjstott 05:06, 7 Apr 2004 (UTC)

A dipole has both a positive and negative charge seperated by distance d. Thus by superposition the Electric Field of the dipole is the field of the negative charge + the field of the positive charge. If you work out the math it becomes an inverse r^3 relationship between E-field and distance. A dipole is 2 opposing charges so the combined effect is weaker than 1 normal charge.

How comes that the dipole moment of methyl chloride is 1.90 and the one of methyl fluoride is 1.85 (so smaller) despite the fact that F has a higher electronegativity? -- In response to your question, my gut answer is that you're not taking into consideration the relative sizes of the Cl and F atoms. F has an incredibly small atomic radius because of its electronegativity, consequently the bond length is much smaller, which means its $\mathbf {r} _{i}$ in the dipole calculation is much smaller. So even though F tugs on all the electrons in CH3F harder than Cl in CH3Cl, this effect in the dipole calculation is offset by how close the F is to the central C. --24.207.160.213 22:26, 4 July 2007 (UTC)

This is the page a search for dipole moment should re-direrct to, not the generic dipoles page.

Direction of moment

The fact that the dipole moment vector is directed from the negative charge to the positive charge is seen to be related to the fact that the plain position vector of a point is directed from the origin to that point.

I don't understand this argument. --Abdull 10:10, 23 October 2007 (UTC)

Template:Electromagnetism vs Template:Electromagnetism2

I have thought for a while that the electromagnetism template is too long. I feel it gives a better overview of the subject if all of the main topics can be seen together. I created a new template and gave an explanation on the old template talk page, however I don't think many people are watching that page.

I have modified this article to demonstrate the new template and I would appreciate people's thoughts on it: constructive criticism, arguments for or against the change, suggestions for different layouts, etc.

To see an example of a similar template style, check out Template:Thermodynamic_equations. This example expands the sublist associated with the main topic article currently being viewed, then has a separate template for each main topic once you are viewing articles within that topic. My personal preference (at least for electromagnetism) would be to remain with just one template and expand the main topic sublist for all articles associated with that topic.--DJIndica 16:38, 6 November 2007 (UTC)

Electric vs electrical

Much more commonly referred to as "electric dipole moment". This comes both from my experience and from a google search showing that "electric dipole moment" results outnumber those for "electrical dipole moment" by a factor of 30.--DJIndica 17:10, 6 November 2007 (UTC)

Free vs bound unexplained

In the derivation where D, E, P, are associated with free, total, and (negative) bound, respectively, there is no definition or motivation of these terms, nor any mathematical formulas relying on the distinction from which we might be able to deduce their meaning. The section ends with:

"Satisfaction of the boundary conditions upon φ may be divided arbitrarily between φf and φb because only the sum φ must satisfy these conditions. It follows that P is simply proportional to the electric field due to the charges selected as bound, with boundary conditions that prove convenient.[8][9]"

The statement "it follows that P is simply proportional to the electric field..." can't possibly follow, because we've said nothing about what P is. 84.227.237.121 (talk) 11:08, 29 March 2014 (UTC)

Electric vs electrical

Much more commonly referred to as "electric dipole moment". This comes both from my experience and from a google search showing that "electric dipole moment" results outnumber those for "electrical dipole moment" by a factor of 30.--DJIndica 17:05, 6 November 2007 (UTC)

Examples

It would be wonderful if somebody place here any examples of dipole moments. For instance, the one of water. Esmu Igors (talk) 17:43, 7 November 2010 (UTC)

Lack of Generality

I have not read the article that carefully, but I can see no mention of the permittivity (e) of the medium in which the charges of an electric dipole are immersed, nor a statement that the discussion relates exclusively to vacuum. As far as I can see, all of the maths expressions include e0 where e*e0 should be written.

One of the references is hanging out of the right side of the reference section.

Number 35 isn't below number thirty four, but off to the right of number one. — Preceding unsigned comment added by 72.187.99.79 (talk) 17:54, 11 June 2011 (UTC)

Notation, notation, notation...

This article has a terrible mix of upright and italic bold letters for vectors - it should be one or the other. Upright is probably more standard so i'll change all italix vectors to upright. Whoever typed those sections really needs to look after what they write - it jut looks unprofessional...

Furthermore - there is, to my dispair, the insane use of fraktur font. I don't care if its in the sources - i'm changing it to mathcal. It is, always has, always will be, the most appauling, disgusting, font ever used in an equation- completley obliterating its apperance and reproductablility of writing down the symbols. It really does look like a scrawn, sprawled up dead spider..... yuck..... An equation should never have to suffer this grotesque appearance, especially for something this useful. -- F = q(E + v × B) 13:59, 27 December 2011 (UTC)

Error in dipole field

Last equation of paragraph http://en.wikipedia.org/wiki/Electric_dipole_moment#Potential_and_field_of_an_electric_dipole should have R^5 in denominator in the first term. — Preceding unsigned comment added by 78.128.169.12 (talk) 15:15, 28 May 2012 (UTC)

Since we are using ${\hat {\mathbf {R} }}$, which is unitless, the denominator should have R^3. --Jebrowne (talk) 04:31, 25 September 2012 (UTC)

Yeah, even I think so. Mentioning polarisation and the resultant relations with the dielectric constant should be added, along with the electric fields along different axes of the dipole. Pranshumalik14 (talk) 17:30, 17 September 2016 (UTC)

This article seriously needs a better summary or overview

Folks, when you start expressing the information in an article using calculus symbols and formulas, you have to realize that 90% of the people who are going to visit the page are instantly lost because they never went beyond high-school algebra. I am NOT saying "delete this or that." I am saying "the information needs to be summarized in an encyclopedic manner, and accessible to the general public that has NO background in science or math." And this isn't the only article like this, there are literally hundreds of articles on wikipedia that have been very carefully structured so only someone with a good deal of science and math background can understand them - you know, precisely the kind of people who don't need to go here to read an article because they already know the information in it.67.0.129.122 (talk) 20:05, 23 July 2016 (UTC)

Yes, thanks, we are very well aware that many articles on WP are for laymen and need rewriting, the problem is largely lack of contribution from editors (myself included, haven't been on WP much lately). For this specific article, the mathematical ground level would most ideally be vector algebra (because that's what the electric dipole moment is, a vector), but a run up to the vector algebra (and subsequent calculus and generalized functions) could be made by elementary algebra and trigonometry. It would take up more space, but may make the article more accessible. I'll try later. M∧Ŝc²ħεИ_τlk 10:42, 24 July 2016 (UTC)

centre of mass vs centre of charge

The paragraph:
"Thus, the value of p is independent of the choice of reference point, provided the overall charge of the system is zero. When discussing the dipole moment of a non-neutral system, such as the dipole moment of the proton, a dependence on the choice of reference point arises. In such cases it is conventional to choose the reference point to be the centre of mass of the system, not some arbitrary origin.[3] This choice is not only a matter of convention: the notion of dipole moment is essentially derived from the mechanical notion of torque, and as in mechanics, it is computationally and theoretically useful to choose the centre of mass as the observation point. For a charged molecule the centre of charge should be the reference point instead of the centre of mass. For neutral systems the references point is not important. The dipole moment is an intrinsic property of the system."
seems very confused to me. I would rephrase:
"Thus, the value of p is independent of the choice of reference point, provided the overall charge of the system is zero, i.e. for neutral systems the dipole moment is an intrinsic property and changing the reference point does not have an impact on its value. On the contrary for non-neutral systems a dependence on the choice of reference point arises. In such cases it is conventional to choose the reference point to be the centre of mass of the system, not some arbitrary origin.[3] This choice is not only a matter of convention: the notion of dipole moment is essentially derived from the mechanical notion of torque, and as in mechanics, it is computationally and theoretically useful to choose the centre of mass as the observation point. Equivalently, for non-neutral systems, the dipole moment can be defined as the total charge times the centre of charge minus the centre of mass. Notice that the centre of charge is instead ill defined in neutral systems."
Davide Sangalli 09:25, 23 August 2017 (UTC) — Preceding unsigned comment added by Dave.bradi (talk • contribs)

Dipole moment as a function of position v.s. a choice of origin

On first reading it appeared that the dipole moment was a function of position in the same way (and denoted with the same notation) that e.g. the E field is a function of position. Reading Jackson 4.1., it is clear however that this isn't the case! What notation p(r) means is that the choice of origin used when setting up the system leads to a different value of p. This is well explained in the article. However, there are many vector quantities that depend on the choice of origin that we would not ever explicitly state – notably a position r depends on the choice of origin, but we would never write r(r)!

The dipole moment is not a field and it should not be implied to be one with the notation p(r). I'd recommend choosing a different notation for the choice of origin e.g. p(o), and state the general definition to begin with without any reference to origin e.g. p = ... . This should leave the previous argument intact without implying that dipole moment varies from point to point in space (as reference to an observer does). — Preceding unsigned comment added by 78.149.209.51 (talk) 19:49, 23 October 2018 (UTC)

Anomalous electric dipole moment

Back in June it was suggested that Anomalous electric dipole moment merge here. That sounds like a good idea, as that's an unreferenced stub that overlaps in content with the Electric dipole moments of fundamental particles section. Klbrain (talk) 07:31, 24 December 2020 (UTC)

  Y Merger complete. Klbrain (talk) 09:01, 30 June 2021 (UTC)