Talk:Magnetism

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Contents 1 Criticisms 2 Magnetism from electron spin 3 Magnetic monopoles 4 Magnetic Attraction 5 Merging of Magnetism and Electromagnetism? 6 Magnetic monopoles: problem sentence 7 Magnetic Refrigeration 8 Magnetic materials 9 Speed of charged particles 10 Hi there. 11 Mention Magnetization in the SI unit table? 12 Persistence of Permanent Magnets 13 Math Parse failure? 14 Magnetic field used as a defensive shield? 15 Vandalism on this article 16 Effect of Magnetism on Strength of Metals

[edit] Criticisms

from the article: "are iron, some steels, and the naturally occurring mineral lodestone?" Since steel is an alloy of iron, and loadstones contain iron, shouldn't the list of natural magnets be changed to "iron, nickle, and cobalt."

Lodestone contains iron, but only in the same way that salt contains chlorine: it is the particular way it contains iron that makes it magnetic. You could change it, but they're only examples - the only importance is that everyone will know what they are.

"Animal magnetism?" I had placed a mention of those idiotic magnetic "treatment" devices being sold at stores onto this page, and someone has changed it to "animal magnetism." If there is no objection, I'll change it back to "magnetic therapy" -- because is the popular name for this bogus "medical" treatment. -- Modemac

[edit] Magnetism from electron spin

If magnetism comes from electron spin, why aren't all elements magnetic, as all elements have electrons? At least the ones, that are not full on the outer layer.

Can someone please elaborate on this? THANKS massa 13:50, 10 Jun 2004 (UTC)

I think that all elements that have unpaired electrons are paramagnetic. Ferromagnestism is a different kettle of fish though. ( I don't know enough about ferromagnetism to discuss it) theresa knott 13:54, 10 Jun 2004 (UTC)

Electrons are divided into electron shells of different energies, with the lower energy levels filling up first. There are even numbers of electrons in each shell, and the electrons in each shell are paired to have spins that oppose each other (one is +.5, the other is -.5, every electron having a spin of magnitude one half, either + or -) so that the total spin of any filled shell is zero. That just leaves the last shell; if it is unfilled but has an even number of electrons, the total spin is again zero, no magnetism. If it has an odd number of electrons, there is an extra unpaired spin, which imparts to the whole atom a net spin of + or - .5. These are the paramagnetic elements, which are so weakly magnetic they are not normally thought of in the real world as magnetic, and require laboratory conditions to demonstrate any magnetic effect. (There are obviously many of them, though).

What are normally in the real world thought of as magnetic elements are ferromagnetic metals: iron, cobalt and nickel, atomic numbers 26, 27, 28. With ferromagnetic metals, because the electron shells are large they have several subshells, and the requirement that all electron spins in the last shell except for maybe one odd electron are paired to oppose each other becomes a requirement that all electron spins in each subshell of the last shell except for maybe one odd electron are paired to oppose each other. That's the trick: unlike electron shells where the lower energy ones fill up first, the subshells are all in the same shell, and therefore at the same? or similarly close enough? energy levels that there can be several partially filled subshells, and there can be an odd number of electrons in each of these partially filled subshells, and these extra unpaired electrons in the subshells can all have the same spin; so that the total net spin for the atom can be several times + or - .5, therefore that many times the magnetic effect.

Rare earth metals have the same thing happening in the next larger electron shell, with even more subshells, so they can have an even higher total net spin per atom than ferromagnetic metals, which is why they can be used for such powerful magnets. (This is a 30 year old memory of what was at the time a very good physics education, so take it for what it's worth). Gzuckier 16:08, 20 Aug 2004 (UTC)

only 1 of the rare-earth elements is ferromagnetic. —DÅ‚ugosz 15:34, 8 Apr 2005 (UTC)

That's still paramagnetism - you have a bunch of atoms with spins of several times .5, but the spins all point in random directions so they don't amount to much. In ferromagnetism nearby spins point in the same direction and their effect adds up. (The ferromagnetism article explains this better) Whether or not the spins line up depends on the type of atom(s), but also on arrangement of the atoms. For example, arrange iron in a BCC lattice and it's ferromagnetic, put it in an FCC one and it isn't. 131.203.9.226 08:08, 14 Jun 2005 (UTC)

[edit] Magnetic monopoles

Contrary to normal experience, theoretical physics predicts the existence of Magnetic monopoles.

Is this still true? Do we have any examples of this viewpoint later than 1931? anthony (see warning) 00:18, 20 Aug 2004 (UTC)

Fang et al., The Anomalous Hall Effect and Magnetic Monopoles in Momentum Space, Science 2003 302: 92-95

Jeon, H. and Longo, M. J. "Search for Magnetic Monopoles Trapped in Matter." Phys. Rev. Lett. 75, 1443-1446, 1995.

Gzuckier 16:08, 20 Aug 2004 (UTC)

I really don't feel that the theoretical justifications are accepted well enough in the physics community to be considered certain. I mean, in my Electricity and Magnetism class part of one of the lectures showed how magnetic monopoles led to a contradiction, and magnetic monopoles have not been shown to exist experimentally. This section on magnetic monopoles should probably mention how conventional electromagnetic theory holds that magnetic monopoles are impossible. Robotbeat 09:51, 20 November 2005 (UTC)

Many have forgotten that in 1905 Einstein explained the fundamental cause of magnetism; the relativistic forces between moving charged bodies. When we analyze magnetism with an understanding of what causes it, it is abundantly clear that there could be no monopoles. But without an understanding of relativity, and under the misconception that magnetism is a fundamental force, monopoles could appear plausible. John 07:00, 8 January 2007 (UTC)

[edit] Magnetic Attraction

Anyone interested in explaining what is the property by which the two pieces of magnetic material are attracted to each other? For example, is the attractive force in the flux lines, or where? What brings them together? wojmax 27 sep, 04

This is elegantly explained under the monopole section. Perhaps it should replace the lead section? John 07:02, 8 January 2007 (UTC)

[edit] Merging of Magnetism and Electromagnetism?

Shouldn't those 2 articles be merged and redirected as un the francophone wikipedia?

Object. Magnetism and Electromagnetism are related topics which were discovered in a historical order. Gilbert built up a theory first (the Earth is a huge magnet). Electricity began to be understood 100 years afterward, with Maxwell unifying the theory 250 years after Gilbert. Further unifications are going on today. Magnetism as a concept is alive and well. Ancheta Wis 21:28, 5 Mar 2005 (UTC)

[edit] Magnetic monopoles: problem sentence

I think there are problems with this sentence: These monopoles, unlike that of elementary particles are solitons, namely localised energy packets. My guess is that it should read: These monopoles, unlike Dirac's elementary particles, are solitons, namely localised energy packets (ie replace "that of" with "Dirac's" and add a comma), but I don't know the subject well enough to be certain. Hv 19:41, 16 July 2005 (UTC)

[edit] Magnetic Refrigeration

Is this topic covered as of yet? I couldn't find it anywhere. Thanks.

Yes . Its covered here [1]

[edit] Magnetic materials

This shouldn't be covered in an article on magnetism. Someone ought to move this section elsewhere. --Smack (talk) 04:59, 16 November 2005 (UTC)

[edit] Speed of charged particles

How fast can a charged particle move in a magnetic field?--Light current 03:04, 29 December 2005 (UTC)

A particle in a magnetic field can have any velocity that is less than the speed of light. But it is misleading to think that the velocity of a charge particle is affected by the magnetic field. The magnetic field only changes the direction of the moving particle, not its velocity. In fact if the particle had no velocity there would be no magnetic force exerted on the particle, even in the strongest the magnetic fields. I wish I could go into more detail but if you look at the equation Fmag=q(v) X B, you will see that the charge particle will travel in a circular path perpendicular to the magnetic field. Its tangential velocity will remain constant while in the magnetic field and its radius will be r such that m(v^2)/r=qvBsin(Θ, where m is the mass of the particle.

I know that this question has gone unanswered for quite some time, but it’s a good problem for anyone that wants to learn about vector cross products and force laws. I I hope people will correct me if I have gotten anything wrong in my explanation.

Later -swimguy112 Feb 2007

[edit] Hi there.

I do strongly believe that magnetism is not fully understood under the light of our scientific knowledge. We know that the whole Universe is crisscrosed by waves emited by stars. Those waves cover awide range of frecuencies and amplitudes. Some are called visible, others are invisible like x rays, radio waves,ultraviolet,micro waves and electromagnetic waves. The electromagnetic waves account for gravity or gravitational fields. Coulhom "law" is the same "law" that Newton created for gravity. Maybe they confused a single magnetic effect as observed in the case of planets and electric charges. And even mmore, perhaps Eistein was weary of gravity as a force as much as a simple ralation of positive and negative charges.He knew that none could explain the cohesive force in atoms and, rather than arguing with his distinguished colleagues prefered the idea of a weak and strong forces, that is yet to be proven. It is clear that magnets cancel gravity as seen with diamagnetic materials, super diamagnetism, super magnetic fields and a lot of diferent "weird" effects used in so many levitating curiosities. --Dr. E. Camps. (201.242.161.177) 23:57, 1 February 2006 (UTC)

Besides being utterly crackpot, beliefs have no place in a scientific encyclopedia article. What's the point? Femto 12:52, 2 February 2006 (UTC)

Dr E Cramps, your ramblings constitute incomensurate loonery.--feline1 15:03, 2 February 2006 (UTC)

Dr. E. Cramps, I'm sure that you are a very clever person (hence your title) but I'm Sure you didn't get it in the research of magnetic effects. Stick to what your good at.

wahehe, ang galing!

uuhhh... I don't even know where to begin with this one, but from what I can tell you are mixing up your forces. The gravitational, electromagnetic, weak and strong are viewed as separate forces in most applications. There are some similarities between their mathematical equations, the gravitational and coulomb forces for example. But the physical mechanisms that drive these forces are very different. So your statement “electromagnetic waves account for gravity or gravitational fields” is incorrect. Gravitational fields are the result of the curvature of space-time while EM waves are the result of interacting electric and magnetic fields produced by oscillating charged particles. Theoretically EM waves can cause gravitational fields however, this is a very extreme case that i dont believe has been done experimentally. There are other problems with your statement but i wont go into them.

You are right to say that we do not know everything there is to know about magnetism but we know enough to harness it for our everyday purposes... and write a wikipedia article about it.

-swimguy112

[edit] Mention Magnetization in the SI unit table?

There is no mention of magnetization in the SI unit table, and little mention of it at all in this page. I'm not qualified to add this kind of info to this page, so I preferred to raise the issue here. I think that this page is rather isolated WRT other magnetism pages... http://en.wikipedia.org/w/index.php?title=Special:Whatlinkshere&target=Magnetization BTW, I've added a "See also" link at the bottom of the magnetic moment page...

[edit] Persistence of Permanent Magnets

How long to "permanent" magnets last? What influences their decay?

Good question. What basically drives it is that the molecules wander away from being all lined up in the same direction. From high school experiments, heat and/or pounding with a hammer both contribute to that. (and if you hold an unmagnetized piece of iron in a strong magnetic field, heat and/or pounding will make it magnetic). Otherwise, I don't know, over time the molecules slowly move? Maybe somebody else can further that. Gzuckier 15:26, 16 August 2006 (UTC)

[edit] Math Parse failure?

When I open the article I get the following message: "Failed to parse (Can't write to or create math output directory): \vec F = q \vec v \times \vec B". Why is this happening?

[edit] Magnetic field used as a defensive shield?

Kind of a dumb question, but hypothetically, could a device generate a magnetic field strong enough to repel bullets?

I would think so, as long as they were conductors of electricity. Not repel, but cause the kinetic energy to be converted to electrical energy and get dissipated in internal resistance inside the bullet. Of course then somebody would shoot you with a wooden bullet. Gzuckier 17:18, 31 October 2006 (UTC)

So what would happen to the bullet when it enters the field? Just fall down?

Yeah, I think it would just slow up, if the field was strong enough it would just fall. Gzuckier 13:32, 2 November 2006 (UTC)

Sweet.

hi ....am sha am doing a project in magnetism..........am having certain doughts regarding inductor.......whenever we design an inductor we will predict its temperature rise above ambient (Theoraticaly)..but in actual case the temperature exceeds our prediction hence it affects the performance of the inductor..which leads to reduce its efficency......i have certain ans regarding this.......but am not compleatly sure about that.......

thank u shah

[edit] Vandalism on this article

There've been a few incidents of apparent vandalism, or at least unintended nonsense edits, by some people in 209.79.65.x domain. I've reverted the latest, but what I neglected to say in my edit comment was that I reverted to the latest edit by VSmith... Sinewalker 00:58, 16 March 2007 (UTC)

[edit] Effect of Magnetism on Strength of Metals

What is the effect of Magnetism on metals such as Iron and steel? Does the presence of magnetism improve the strength of the metal? Does it make it more elasitc? Does it weaken it? Do these changes persist once the magnet is removed from the metal? —The preceding unsigned comment was added by 71.127.246.251 (talk) 14:56, 26 March 2007 (UTC).