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Listed on Misplaced Pages:Votes for deletion Feb 20 to Feb 26 2004, redirected. Discussion:

• Biot-Savart law - text has nothing to do with the Biot-Savart law]] Fuzheado 23:18, 20 Feb 2004 (UTC)
  • I've redirected it to Biot-Savart's Law. Maximus Rex 23:42, 20 Feb 2004 (UTC)
  • I switched them the other way, since the preferred usage is tends to be without the apostrophe. -- Decumanus 08:57, 21 Feb 2004 (UTC)
  • List on redirects for deletion as copy/paste move which needs to be fixed. Anthony DiPierro 16:22, 21 Feb 2004 (UTC)

-- Graham  :) 21:08, 26 Feb 2004 (UTC)

In fact, the use of the apostrophe is clearly wrong. It implies that there was a single person named 'Biot-Savart', whereas the two names in fact belong to two different people. I'm going to fix all pages that link to the bad spelling. --Smack 00:40, 15 Nov 2004 (UTC)

Laplace's Law

I was looking for this version of Laplace's law: http://hyperphysics.phy-astr.gsu.edu/Hbase/ptens.html#lap Can someone either fix the redirection, maybe add a disambiguation, or explain where this should correctly fit?

first sentence; more general form?

The Biot-Savart law describes the magnetic field set up by a steady current density.

This is true, but as later noted in the article Biot-Savart is used extensively in aerodynamics. In fact it has been the lynchpin of all vortex models of flows around bodies for the past 70 years. Given its prominence in aerodynamics, shouldn't the first sentence of this article be changed to more generally describe application of Biot-Savart?

I made an attempt to modify the intro as you suggested. Feel free to improve it, expand it, or revert and start over. -- Metacomet 01:38, 27 December 2005 (UTC)

Just thought someone should know, I searched on Laplace Law, and got the following link: http://en.wikipedia.org/Laplace%27s_Law however, the article i got was Biot-Savart Law... I see no obvious connection between them. //Wikipedia reader ;)

Really, there are two different uses of the name "Biot-Savart law." One is the strict use in the E&M sense of finding the B field from a current, the other is the basic math of inverting a curl. Inverting the curl is all you are doing in finding B from J, and it's also all you are doing to find v given the vorticity in a fluid. You could also use it to find A (the vector potential) from B, up to gauge, or whatever. I think it makes more sense to separate out the core mathematical concept in the Biot-Savart law, somewhere on this pagePetwil 06:01, 8 September 2006 (UTC)

pronunciation

how to pronounce "Biot-Savart"?

-- As they are French, probably the correct is without trailing "t", but this is only a guess. The rest I suppose is pronounced phonetically. -- Mtodorov 69 14:24, 4 May 2006 (UTC)

I tried doing phonetic but I can't get the unicode to print right. Bee-oh, followed by sa like sa in sand but a bit more like "ah" as in "ah I see", art like the English word art but without the t, and with the r pronounced like a French r - fricative, swallowed r on the roof of your mouth, not the front of your mouth. But that won't do for the entry, eh? I dunno how to do the French phonetic unicode.... :)Petwil 06:24, 8 September 2006 (UTC)

Factors of 2

...are easily lost in this subject. I've 'corrected' to my understanding (Batchelor, 'Fluid Dynamics', eqn 2.6.4) - if you think I'm wrong, I'll need a reference. Linuxlad 13:20, 22 January 2007 (UTC)

geneneral statement first?

Could we see a general statement of this law in terms of vector analysis first, and then its applications to electromagnetics and to aerodynamics afterwards? Michael Hardy 02:12, 13 March 2007 (UTC)

The Introduction

While the application to aerodynamics is very interesting, it is not something that people expect to read in an introductory paragraph about the Biot-Savart law. A full section on the aerodynamics parallel and applications is nevertheless most welcome, but we should not overlook the fact that the law was first conceieved of in conjunction with electromagnetism and it is with electromagnetism that it is primarily associated.

The issue of the Biot-Savart Law being the inverse of the curl operator may be a matter of technical interest to mathematicians but it is hardly suitable material to include in the introductory paragraph. It's a bit like saying that a quantity is the product of two quotients. David Tombe 16th April 2007 (125.24.135.73 09:55, 16 April 2007 (UTC))

Coordinate Frame Origin

The Biot-Savart law contains the inverse square law of distance.

If we consider electromagnetic radiation deep in space, where do we fix the origin of the coordinate frame within which the inverse square term of the Biot-Savart law is measured? David Tombe 17th April 2007 (125.24.192.94 16:21, 17 April 2007 (UTC))

Lorentz Transformation

The Lorentz transformation acts on the full electromagnetic field tensor to produce the Biot-Savart law. See http://hepth.hanyang.ac.kr/~kst/lect/relativity/x850.htm This tensor already contains the magnetic vector potential term A. If we remove A from the equation, we cannot obtain the Biot-Savart law. Therefore it is not true to say that the Biot-Savart law can be obtained by applying the Lorentz transformation to Coulomb's law. We need to have the full set of Maxwell's equations to begin with. (86.155.139.178 21:47, 9 July 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 (i.e. current) 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 16:46, 6 November 2007 (UTC)

Undefined constant

A constant ${\displaystyle K_{m}}$ begins to appear half way down page without any definition nor word of explanation. —Preceding unsigned comment added by 138.40.94.135 (talk) 18:14, 15 January 2008 (UTC)

Showing that Ampère's circuital law is the curl of the Biot-Savart law

Take the curl of,

${\displaystyle \mathbf {B} =\mathbf {v} \times {\frac {1}{c^{2}}}\mathbf {E} }$

This expands into four terms under the product rule. The two v terms vanish since v is a vector and not a vector field. The two terms left are v(div E) and (v.grad)E.

The former is equal to ρv which equals J. the latter is the convective term which we ignore at stationary points in space.

Hence curl B = J. This is Ampère's circuital law.George Smyth XI (talk) 06:18, 5 April 2008 (UTC)

If you're suggesting that the "derivation" of Ampere from Biot-Savart be put in, it seems reasonable and topical enough. It would probably be better to use a derivation that starts from the common form of the Biot-Savart law, instead of starting from the unconventional form in terms of E. See Jackson p178-9 for this derivation, for example. We can also put in the "derivation" of Gauss's law for magnetism while we're at it, see Jackson p179. Maybe we can use show/hide boxes to not clutter up the article with vector manipulations? --Steve (talk) 17:33, 5 April 2008 (UTC)

Steve, you asked for a citation for the above expression. That is hardly necessary. It follows directly from the previous section. Anyway, here is web link which backs it up. it's at about equation (19). http://hepth.hanyang.ac.kr/~kst/lect/relativity/x850.htm George Smyth XI (talk) 08:02, 6 April 2008 (UTC)

Well everything I've seen, including that link, indicate that this is the formula for the magnetic field of a point charge moving at constant velocity (changing neither direction nor speed). The section itself makes it sound more general than that, so I rewrote and resectioned accordingly. I'd still like to see a citation for any expression in that section being called "the Biot-Savart law", as opposed to "the formula for the magnetic field of a point charge moving at constant velocity" :-) --Steve (talk) 18:04, 6 April 2008 (UTC)

Steve, I'm happy enough if you put in the derivation of Ampère's circuital law from the Biot-Savart law. Try it for a few days. If it appears too cluttered then you can always side link it.

When you look at that derivation, you will notice that the inverse square law aspect of Biot-Savart plays no role in obtaining the current density term. George Smyth XI (talk) 09:58, 7 April 2008 (UTC)

Steve, Now that you have put in the derivation, I don't actually think that you need to offer the 'hide' option. I think it should form a full section in its own right. It shows that the Biot-Savart law is a solution to the differential form of Ampère's circuital law within the context of current understanding at textbook level. It is a well presented piece of information.

One point however worth noting is that as the curl of B is undefined at the origin, we cannot say that div B is zero everywhere. We have a dilemma which cannot be resolved within the context of current textbook level knowledge. I do however believe that it can be resolved, but that we will have to modify our understanding of the physical meaning of the terms in the Biot-Savart law. I don't think that the inverse square law applies on the large scale. George Smyth XI (talk) 11:47, 10 April 2008 (UTC)

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