Talk:Diamagnetism

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[edit] Helium

I edited the third paragraph to exclude helium. Helium only contains S-shell electrons which have no angular momentum and thus cannot be effected by magnetic fields. Beryllium and magnesium, in their metallic state, have P-shell states which overlap with the S-shell electrons and thus can be paramagnetic at temperatures greater than 0K. —Preceding unsigned comment added by 149.169.54.225 (talk) 20:39, 31 January 2008 (UTC)

[edit] Levitating frogs

I think this article can't be complete until we find a free image of a levitating frog! I'll have a hunt... OK managed to get permission from Nijmegen High Field Magnet Laboratory. CharlesC 14:31, 19 December 2005 (UTC)

I am surprised to be the first to ask this question: since the lab boys now now have gizmo that can levitate anything that can fit inside of it, when can we expect to see a gizmo that can levitate itself?Kalaong (talk) 07:47, 18 April 2008 (UTC)

[edit] Explaining the leviation experiment

(Mouvement, 22 Jan 2005) At the end of the article page, there is a description on how to make a diamagnet leviate. Does anyone know the reason, why this is stable?

I just clarified it, let me know if it does or doesn't make sense.Pkeck 18:54, 6 May 2005 (UTC)

[edit] Diamagnetic materials table

Can you insert a table of diamagnetic materials? i.e.

Bismuth -16.6 Mercury -2.9 Silver -2.6 Carbon (diamond) -2.1 Carbon (graphite) -1.6 Lead -1.8 Sodium chloride -1.4 Copper -1.0 Water -0.91

etc...

Almost everything is diamagnetic. Many metals are para-, a few are ferro-, but dia- is the most common, especially given the wide variety of organic materials. BTW, you forgot the exponents. But here are a few more entries, from Halliday, Resnick, & Krane (ISBN 0-471-54804-9):
Bismuth -1.7 (you have 1.66, which I'll accept) e-5
Mercury -3.2 e-5 (different from yours by ~10%, but HR&K sucks as physics books go)
Silver -2.6 e-5
Carbon dioxide (STP) -1.1 e-8
N2 (STP) -5.4 e-9

And from this site:

Material χv / 10-5

Ammonia -1.06
Bismuth -16.7
Copper -0.92
Hydrogen -0.00022
Silicon -0.37
Water -0.90

Enjoy. --Joel 05:53, 12 May 2005 (UTC) PS: Whatever compilation table ends up coming together, we should probably mention that the values are volumetric & dimensionless.

I'm not sure why, but the table I got looks like this:

  • Material 2 x(31026)
  • Water 8.8
  • Bismuth metal 170
  • Graphite rod 160
  • Pyrolytic graphite ' axis 450
  • Pyrolytic graphite i axis 85
Tell Me Why!!

[edit] Major Cleanup Needed

I re-added the cleanup and accuracy tags. The tone of the whole article is very informal and inappropriate and there are egregious factual inaccuracies in the superconductor/MRI explanations (for starters). A physicist (or at least someone who really knows what they're talking about) is badly needed to clean this article up. --Deglr6328 04:29, 29 September 2005 (UTC)

You're not the first to say that, and yet no one gives any examples of what they think is wrong. I don't see any informal tone or factual errors. — Omegatron 13:45, 29 September 2005 (UTC)
The diamagnetic levatation section reads like a science fair project when it should actually be a lucid explanation of the physics behind said phenomenon and after that should come a demonstration section. --Deglr6328 23:19, 29 September 2005 (UTC)
Also, in the diagram of the suspended magnet, field lines cross. Field lines NEVER cross. I do not have the means to fix this mastodon 21:55, 26 November 2005 (UTC)

I agree that a major clean-up is required. For instance, the claim that "[a]ll materials, except helium, show a diamagnetic response in an applied magnetic field" is false. Not only is helium actually diamagnetic, there are also many substances that are paramagnetic (e.g. molecular oxygen) or ferromagnetic (iron, nickel, cobalt). Oleg Tchernyshyov (talk) 23:33, 2 February 2008 (UTC)

[edit] Explanation involving electromagnetic force rather than Faraday's Law

We changed the explanation of the cause of diamagnetism to reflect the fact that it does not result from electromagnetic induction as described by Faraday's Law. Faraday's Law is an induced electromotive force that results from a changing magnetic field. Diamagnetism exists whether the external field is changing or not; it is the result of the qvxB electromagnetic force on individual electrons. This is incorrectly explained in about half the Physics textbooks we've seen. Any suggestions?

Quantum Spin Coherence In modelling electron correlation effects in close-coupled pairs, I have developed a new thesis of coherent distributed matter-wave spinor interactions. This model, the quantum spin coherence (QSC) model, has interesting ramifications not only in elucidating the underlying physics of diamagnetism, but also - ! - is relevant to the extremely weak orienting force between massive objects that we know of as gravity. see http://homepage.mac.com/blinkcentral/Menu7.html (Paper being presented at 17th AIP Conference, Brisbane Dec 3-8, 2006) [1]--peter g burton 23:53, 14 November 2006 (UTC)

Lorentz force does NOT change the speed of the moving charged particle because the force is always perpendicular to the velocity! Only the direction changes which effectively changes the size of the "current loop" of the orbitting electron (classical picture). Changing the loop size would change the magnetic flux hence current is induced whose field will oppose the applied field.

[edit] Effect of diamagnetism on water

Sorry for this being a bit off topic, but I couldn't think of a better place to ask: Using no special equipment, is there any way to demonstrate diamagnetism of water with just a standard magnet?

My ideas were things like putting a magnet into a fine mist, and watch for changes in the density of the mist. Would that work? —The preceding unsigned comment was added by Wierdy1024 (talk • contribs) 23:13, 7 December 2006 (UTC).

A common demonstration of this is to put a very strong NIB permanent magnet (N45 or more if you can find it, and a half inch or more across) at the bottom of a petri dish, and add just enough water to slightly cover the magnet. Google shows several sites with photos of this, such as http://www.matchrockets.com/water/diamagh2o.html ... --Splarka (rant) 08:10, 8 December 2006 (UTC)


I have taken a long soda straw, filled it with water, and frozen it. Then I suspend the straw on a string. Using a powerful rare earth magnet, I can show that the end of the straw is repelled by the magnet. Freezing *really* helps and it seems, the colder, the better. I am using an half pound rare earth magnet that is very powerful...arguably dangerously so. This may not qualify as a "standard magnet". Paul Hite

[edit] vector field terminology

"Diamagnets are also attracted to field minima, and there can be a minimum..." Wouldn't the diamagnetic be repelled too the field minima rather than attracted to it?

[edit] Diamagnetism in the home

There is a source that can be cited for the last paragraph in the entry: http://www.unitednuclear.com/magnets.htm The second last section on that page is about Diamagnetism and a bismuth display setup kit. 143.117.120.104 (talk) 09:21, 16 January 2008 (UTC)