Talk:Magnetism

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Error in magnetic domains image

I remember my previous physics teacher said that this image: http://en.wikipedia.org/wiki/File:Ferromag_Matl_Magnetized.JPG in the Magnetic domains section is wrong. The arrows should go from north to south. I never really understood his argument so I'm just asking that somebody with more knowledge in this subject take a look at it.

Antonio92 (talk) 08:31, 21 June 2012 (UTC)

Confirmed: Outside a magnet the lines definitely go north to south. (Inside the B field goes S-->N, the H field goes N-->S.) I corrected the image. (It sometimes takes a day or two before the up-to-date image thumbnail gets put on the page.) --Steve (talk) 14:30, 21 June 2012 (UTC)Subzbharti (talk) 18:13, 21 March 2013 (UTC)

Problem with figure

Hierarchy of types of magnetism.[7]caption in the diagram are blurred and not readable. Please edit them suitably. thanks — Preceding unsigned comment added by Subzbharti (talkcontribs) 18:13, 21 March 2013

I know how hard it is to write the introductory sections for topics like this, and how it tends to generate endless edit wars over minor wording differences. I don't mean to criticize the hard work that has been done on this article. But I feel I don't understand the lead sentence:

Magnetism is a class of physical phenomena that includes forces exerted by magnets on other magnets.

Doesn't magnetism also include forces exerted by magnets on materials which are not magnets? And I'm wondering if the term magnetic field should be introduced earlier, in the first sentence, instead of the 3rd. --ChetvornoTALK 23:32, 19 September 2014 (UTC)

I've tweaked it, hopefully addressing your immediate concern (I agree that it was probelmatic); see what you think. —Quondum 00:09, 20 September 2014 (UTC)
That looks a lot better to me. I like the lead sentence, it a good definition. --ChetvornoTALK 00:27, 20 September 2014 (UTC)

Unified Field Theory and Magnetism

We adventure into UFT by assuming there is but one source of forces, and that all forces can be explained by characteristics of a space with nothing but relative levels of compression. This means the concept of electromagnetic charge as a characteristic of particles is forbidden.

Mass acquires the definition of an expansion of space, compressing space around it. (Hence it is relative like spacial measurements, and hence it is energy.)

This definition reconciles the strong and nuclear forces rather easily. Two particles of mass that get too close push each other away encompassing the strong nuclear force. The sphere packing of an atomic nucleus, or a star containing black holes, creates suction between its component particles and towards its interior as it expands, encompassing the weak nuclear force. The misshapenness of the compressed space is responsible for gravity. But what is magnetism?

What is magnetism? Why do the same poles of magnets repel and opposites attract? Well, if you spin a massive particle about an orbit you generate a corkscrew shaped object in space time. As two magnetic poles opposite in polarity approach their spin is in the same direction which reduces antagonism from the expanding objects. Conversely, if two magnetic poles identical in polarity approach, their direction is opposite and they plow into each other increasing expansive antagonism.

Magnets, whether the planet earth, a bar magnet, an electromagnet, a gyroscope, all generate their fields through the rotation of mass in the same direction with some preponderance. — Preceding unsigned comment added by GuildCompounder (talkcontribs) 00:19, 1 April 2015 (UTC)

Sources of magnetism

The section on Sources of magnetism describes two sources - current and the nuclear moment - before launching into a discussion of the electron magnetic moment. No connection is explained between the list of sources and the subsequent discussion. Can this be added? 83.104.46.71 (talk) 08:59, 10 May 2015 (UTC)

I agree; the electron magnetic moment seems to be inexplicably lumped in with electric current. I think the second bullet point, nuclear dipole moment, should be expanded to include all particle dipole moments. --ChetvornoTALK 09:31, 10 May 2015 (UTC)
Me three. The magnetic moment associated with the orbital angular momentum of an electron should presumably also be included in the second point. But perhaps we should not be trying to classify the sources so distinctly into two categories; rather it might be better to simply list several contributors: electric current (flow of electrons, ions and any charge-carrying particles generally), intrinsic spin of elementary particles, orbital contributions. Technically, nuclear magnetic moment arises from a combination of the last two of its constituent particles. —Quondum 16:28, 10 May 2015 (UTC)
I can see that point of view, but my feeling is it would better to limit the bullet points to the fundamental sources, currents and intrinsic spin. Orbital magnetic moment can be understood as a circular "current" of charge about the nucleus. This can be explained in the following text. Explaining it that way would give entry-level readers a more intuitive understanding: charge + motion = magnetic field --ChetvornoTALK 17:45, 10 May 2015 (UTC)
That might not be so rigorous. It works as an intuitive explanation. However, I expect that the magnetic moment due to intrinsic spin of a particle falls into the same explanation (rotary current), and is indistinguishable at a mathematical level. I don't think that it is for us to be making such hazy, ill-defined distinctions. —Quondum 18:47, 10 May 2015 (UTC)
Kittel lists the principal sources in a free atom as electron spin, electron orbital angular momentum, and the change in angular momentum induced by an applied field. The first two give rise to paramagnetism and the third to diamagnetism. This satisfies the desire of the IP editor for a connection between sources and phenomena. Note the focus on a free atom, with ordered arrays of moments to be discussed separately in connection with phenomena like ferromagnetism. Similarly, electron currents as sources primarily arise in connection with electromagnets. Nuclear magnetic moments are 1000 times smaller than electron magnetic moments, so they should not be listed as principal sources. 03:44, 11 May 2015 (UTC)

What is magnetism?

I wish the article explained, in terms a non-physicist and non-mathematician (me) could understand, what magnetism is, why magnetic fields exist, why similar poles repel rather than attract. Is this impossible to explain in simple language? Is it even known? deisenbe (talk) 11:38, 11 October 2015 (UTC)

@Deisenbe: Sorry it has taken so long to reply. I think I can do no better than point you to this interview with the Nobel Prize-winning physicist Richard Feynman. He'll give you a taste for how hard the "why" questions are. 20:28, 30 October 2016 (UTC)
I think Deisenbe is just asking for a layman's introduction to magnetics. @Deisenbe: physics does know a great deal about "how" and "why" magnetism works, including the answers to most of your questions. It is just that it is rather long and involved, and in an article like this it is hard to find a level of explanation that will satisfy everyone; a "simplified" explanation that is comprehensible to general readers raises objections from scientifically-educated readers who regard it as "incomplete" and a lie-to-children. Here are some links [1], [2], [3], [4], [5], [6], [7], [8], [9] to elementary explanations of magnetism. --ChetvornoTALK 08:28, 1 November 2016 (UTC)
Since it's not really covered elsewhere, perhaps this article should include an elementary section (with some good diagrams) on the everyday questions Deisenbe is asking; the basics of ferromagnetism:
• The magnetic field is one aspect of the electromagnetic force, which is one of the 4 fundamental forces of nature.
• Magnetic fields are created by moving electric charges and magnetic dipoles.
• Magnetic fields exert forces on moving electric charges and magnetic dipoles.
• A few substances, the ferromagnetic ones, are strongly attracted to a magnet; these same substances can be magnetized to become permanent magnets.
• The difference between magnetized and unmagnetized ferromagnetic material is that in a magnet many of the atomic dipoles are lined up.
• Magnets have two poles, and you can't get an isolated pole by cutting one in half.
• Like poles repel, unlike poles attract.
• Magnetic field lines could be introduced, and the reason for attraction and repulsion could be explained by field line diagrams; an attractive force is exerted along field lines, and a repulsive force between adjacent field lines.
--ChetvornoTALK 08:28, 1 November 2016 (UTC)
Indeed, something like that would be a good idea. Many of these concepts are scattered through the article, but it would be hard for a beginner to find them. I would de-emphasize the magnetic field, which in any case has its own (much more frequently visited) site, and concentrate on phenomenology (poles, currents and how they interact). It would also help to improve the ties between the three main articles: magnetism, magnet and magnetic field. 16:17, 2 November 2016 (UTC)

Magnetism/String Theory/Quantum Physics

Speculation: This is probably not new but at one time or another we have all been given the thought experiment of a three-dimensional ball moving through a two-dimensional world. For argument's sake let's say what the scientists are observing of the three-dimensional ball they call an “atom”. They mark its position and move on (two- dimensionally) in a measurable way to the next “atom”. At this point they shift the relative position of the “atom” (two- dimensionally) and then returned to their original starting point finding the first “atom” has shifted its relative position the same way as the second “atom”. If you were taught like me you were told they would first see a dot as the ball started to pass through their word. The dot would get bigger and bigger until the diameter was reached then shrink back down to nothing. But a ball made up of matter as we currently know it is made of atoms; mostly space. So only the part of the atom intersecting their world could be observed. If the ball was stationary the “atom” would look like a fussy quivering object as the atom is vibrating. There could be many of these objects intersecting their world. They most likely could not detect the momentary arrival and exit of the atom's electrons do to their size and speed. Scientists being scientists would run experiments on the object; one finding some free to rotate materials would align to the nearest “atom”, referring to the effect as “magnetism”.James Brian MacDonald 12:14, 24 December 2015 (UTC) James Brian MacDonald 12:04, 24 December 2015 (UTC) James Brian MacDonald 11:52, 24 December 2015 (UTC) — Preceding unsigned comment added by James B MacDonald (talkcontribs)

Minor confusion in lead

I don't mean to nitpick, and the article looks good, but I noticed a slightly confusing point in the introduction. The intro says

"Every material is influenced to some extent by a magnetic field."

and goes on to describe ferromagnetic, paramagnetic and diamagnetic materials. But then it says:

"Substances that are negligibly affected by magnetic fields are known as non-magnetic substances. These include copper, aluminium, gases, and plastic."

Aren't (most of) these actually paramagnetic or diamagnetic? I feel this will be confusing for general readers. It seems to me the term "non-magnetic" is not a scientific term, but just an everyday label applied by the public to all nonferromagnetic substances, since the force of a magnet on paramagnetic and diamagnetic substances is not strong enough to be felt. How about replacing that sentence with something like

"The force of a magnet on paramagnetic, diamagnetic, antiferromagnetic materials is usually too weak to be felt, and can only be detected by laboratory instruments, so in everyday life these substances are usually described as non-magnetic."

--ChetvornoTALK 00:16, 30 October 2016 (UTC)

I wouldn't call paramagnetic substances like aluminum non-magnetic. Their induced magnetization is much stronger than diamagnetism (indeed, diamagnetism is always present in paramagnets but it is negligible by comparison). I saw a nice demonstration once where someone dropped a rare earth magnet through an aluminum tube, and because of Lenz's law it took several seconds to drop a meter. 16:49, 7 November 2016 (UTC)
Right, scientists don't call paramagnetic substances "nonmagnetic", so if we're going to apply the word "nonmagnetic" in the intro to paramagnetic or diamagnetic substances it needs to be made clear that this is a nonscientific usage. Yeah, dropping a rare earth magnet through a metal tube is a great demonstration, but of course it doesn't have anything to do with paramagnetism; the magnet is slowed by eddy currents induced in the metal. --ChetvornoTALK 19:46, 7 November 2016 (UTC)
You're right - I was a bit brain dead when I wrote that. 01:01, 8 November 2016 (UTC)

Manganese

This article says manganese is antiferromagnetic, but the article for manganese says it's paramagnetic. I don't know which is right, but someone who does should fix whichever article is wrong. Maybe they meant to say that the alloy iron manganese (FeMn) is antiferromagnetic, rather than pure manganese, which is paramagnetic. Although I'm not sure. - 72.184.128.205 (talk) 20:11, 2 December 2016 (UTC)