Talk:Magnet

fUcKiN mAgNeTz ! !

HOW DO THEY WORK!?

Force

According to the 14th citation in Magnetic dipole moment Boyer, Timothy H. (1988) The Force on a Magnetic Dipole. American Journal of Physics 56 (8): 688–692. doi:10.1119/1.15501. Using the electric dipole formula for the case where the magnetic field is rotational ($\nabla \times {\vec {B}}\neq 0$) is not correct. Two bar magnets do have a rotational field, hence the calculation given could be not correct. The webpage cited here http://instruct.tri-c.edu/fgram/web/Mdipole.htm uses the electric dipole approximation, which according to the paper is not correct. Aslo, looking at the formula given in Magnetic moment for th einteraction of two coils when separated a big distance, shows a $r^{-4}$ dependecy while, the formula given here dependos on $r^{-2}$, where $r$ stands for the distance. I guess this difference comes form the shape effect of the bar manget, but it should be verified. In the webpage where the calculations are shown this is not explained. The formula is obtained directly from the electrical analogy. --Kakila Monday, October 26 2009 —Preceding undated comment added 15:11, 26 October 2009 (UTC).

And my the force be with you. —Preceding unsigned comment added by 82.132.19.153 (talk) 19:41, 14 April 2010 (UTC)

Magnetic motors

Would Wikipedia consider a listing for a speculative field such as Magnetic Motors?

See: http://www.pureenergysystems.com/os/MagneticMotors/

The above question was part of the the exploration by a user who came and left in December 2003 of what Wikipedia isn't, and he seems to be part of a consensus that the answer is "no". --Jerzy 05:50, 2003 Dec 19 (UTC)

North-seeking

The article (Magnet) says

The end of a freely suspended magnet that starts to point towards the Earth's geographical North Pole, is by definition the magnetic south pole.

And no, i'm not about to point out that the geomagnetic field repeatedly reverses.

It's an even more pedantic issue than that, but i think i recall that what gets labelled N by convention is a north-seeking pole rather than a north pole, from which it follows that the geomagnetic pole in the northern hemisphere is a south pole. Maybe my instructor got befuddled in trying to talk about red end of the compass needle not being a north pole, but the consequences of being wrong about this are so small that 90% of confident sources could be wrong and never realize it. Does someone have a super-reliable source on this? --Jerzy 05:50, 2003 Dec 19 (UTC)

I just checked this out myself using the following procedure:

1. I set up a small electromagnet (wire around a bolt).
2. I connected a 9 volt battery to the wires.
3. Using the right-hand rule (as defined on wikipedia), I set my hand on the coil such that my fingers were pointed in the from-positive-to-negative-direction.
4. My thumb indicated which side was north (and then I labeled both sides with a sharpie).
5. Then I set a stack of neodymium magnets near the magnet, and let them orient themselves on the table.
6. I labeled the side of the magnets that faced the south side of the electromagnet as north.
7. Then I suspended the magnets with a thread, and let them orient themselves.
8. The north side of the magnets pointed toward geographic north, which means that the geographic north is actually a magnetic south pole.
9. To make sure that the string wasn't twisted (or that something else wasn't forcing the magnets to move), I did everything I could to spin the magnets the other way. I twisted the thread in both directions, I moved the magnets to the middle of a room to account for any interactions with things in the room, and then I tried to point the magnets in the wrong direction. They always re-oriented themselves such that their north pole pointed toward the geographic north.

--Pkeck 15:10, 2005 Jan 14 (EST)

I did a similar experiment, but constructed a coil on a piece of wood with a aa battery. The N end of the coil, determinde by the right hand rule, pointed north when the wood was floated on water. Edison 22:30, 15 November 2006 (UTC)

The Earth's geographic North pole is a magnetic South pole. The "N" end of a magnet will point to geographic North. SimpsonDG (talk) 13:00, 1 March 2009 (UTC)

Revamping this page

I started to rework this page with the hopes of making it much clearer and more organized. I feel that magnets are one of those topics that the average person might be interested in, so the content here shouldn't be too in depth. If they want more information, that's what the links are there for. If anyone sees anything that isn't clear or feels that something is missing, please help out. --Pkeck 11:21, 2004 Jan 14 (EST)

New Section on "Explaining Magnetic Attraction"

I'm curious about this new section. First (and most importantly), is this really an accurate way to describe what's going on in a magnet? I've never heard of or thought about it this way...which isn't to say that it's wrong, I've just never heard about it. Can you point to a page with more explanation of this idea of net current flowing around the surface of the magnet? I understand exactly what you mean, I just haven't ever heard of it.

Second, is it really easier to understand why magnets attract or repel one another through this explanation? I'm thinking that if you told the average person to imagine a cylinder of current carrying loops that all had current flowing perpendicular to the long axis of the cylinder and all in the same direction...and then to imagine how the current of adjacent loops negates the flow of current in their neighbors because they are flowing in opposite directions at adjacent points...which means that there will only be a net flow around the surface of the cylinder...I'm thinking the average person would be completely lost.

To be honest, it seems much more complex than simply saying that each atom is a dipole, which makes the whole magnet a dipole, and when opposite poles are near one another, there is attraction (and vice versa). To sum up: is this explanation correct? And is this explanation really more simple? Pkeck 21:11, 17 Feb 2005 (UTC)

Fully agree a new Section on "Explaining Magnetic Attraction" is needed. For instance I came to this article to understand why a)iron is atracted by a magnet and b) why a magnet is attracted by another magnet, and I came empty handed (unless I missed it) Manuel

  Agreed - something to address the question "what on earth IS a magnet and why do things stick to it" for us mere mortals would be good.  An answer something other than "it's magic"!!!  —Preceding unsigned comment added by 132.185.144.122 (talk) 17:12, 12 March 2010 (UTC) 

Permanent magnets

I'd want to know, in these permanent magnets, is the magnetic field constant, or will it drain when used? And if so, will it regenerate? Take the average ABC hanging on your fridge. Will they come down due to weakened magnetic properties? Naturally one would assume that eventually they should come down, due to energy transformation. But I have yet to see a magnet fall down/stop beeing magnetic. So basically, is there any info on energy in permanent magnets?

A magnet does not lose energy by being used, and will stay on your fridge forever unless something happens (such as heating, shock or a strong external magnetic field) to demagnetise it. There is no "energy transformation", as you put it. The magnet is not using any energy ("doing work") to stay stuck to the fridge, because work = force x distance moved, and nothing is moving. The only energy transfer occurs when you stick the magnet to your fridge in the first place. As the two objects approach, some of the magnet's field goes into the metal of the fridge, resulting in a decrease in the field's energy (technically speaking, you are decreasing the reluctance of the magnetic circuit). The energy released from the magnetic field goes into pulling on your arm muscles, which turn it into heat. If you pull the magnet off the fridge, your muscles have to put that same amount of energy back into the field. You can do this as many times as you like without draining the magnet, because the energy is coming from you, not from the magnet.

There is some energy stored in the magnetic field of a permanent magnet, equal to the energy that was put in to magnetise it in the first place. This PDF is a good reference on the subject. This other PDF is good at explaining how permanent magnets work. Both of them discuss how to calculate the energy stored. --Heron 19:53, 27 July 2005 (UTC)

Iron filings

Do iron filings actually show the lines of magnetic force of a magnet, or do they just show how iron filings line up when they disturb the magnetic field of a magnet? --Light current 10:26, 21 September 2005 (UTC)

The former. Give it a try yourself. Salsb 11:45, 21 September 2005 (UTC)

I think the filings disturb the free space field of a magnet. I think filings show this disturbed field, but which resembles the undisturbed field. John (talk) 06:11, 11 September 2008 (UTC)

Post copied from magnetic field

Field lines are just diagrammatic. The number drawn in any given diagram is arbitrary, the field is smooth, not ridged. Lines are just one way to show the direction and magnitude of a vector field at every point on a plane. Iron filings tend to mimic the shape of diagrammatic field lines, because adjacent lines of iron filings tend to repel each other, and because grains that are in contact tend to line up end-to-end with unlike poles touching. -- Tim Starling 12:32, Jun 24, 2005 (UTC)

But the average permeability in the plane of the paper has been increased cf that of air. So this will distort the field?--Light current 14:52, 21 September 2005 (UTC)

No one really understands the mysterious energy permanently stored in magnets. Most explanations are only theory based. So don't feel scared that mankind doesn't know how something works.

We're here to explain things, not to ascribe mystical qualities to phenomena!--Light current 23:45, 12 July 2006 (UTC)

Units

What's the point of having the units of force in the introduction? The attraction or repulsion is already indicated, and the units are irrelevant. Salsb 12:56, 21 September 2005 (UTC)

Deleting and clarifying the comparison of Gaussian-CGS to SI-MKS units. SI is not replacing the "older" CGS units. Maybe in some fields, but in physics we (almost) never use SI for electrodynamics. Also, mechanical CGS is primary in chemistry. SamuelRiv 20:02, 14 October 2007 (UTC)

I think there must be a difference in practice and terminology between the US and Europe (maybe the rest of the world). CGS units are never used here in the UK - I last used them back in the 1960s when at school. Since then everything has been exclusively SI (MKS at first, as the SI system developed). The scientific community universally uses SI, and the use of other units should be deprecated.

I have noticed that authors from the US consistently make what appears from our perspective to be an error of terminology concerning B, H and the word 'field'. 'Field' can refer to a region of magnetised space (in this context), but as a physical quantity it is exclusively reserved for the quantity symbolised by H and measured in units of A/m. B, referred to in your units paragraph as 'the true field' is the symbol used for flux density, measured in Teslas. It is important to distinguish correctly between B and H , field and flux density, so the perpetuation of confusing (and confused) terminology is unfortunate. Can this be corrected please ? Andrew Smith —Preceding unsigned comment added by 82.32.50.77 (talk) 17:20, 28 June 2009 (UTC)

What you think is a difference between UK and US is in fact a difference between engineers and physicists. --Steve (talk) 21:41, 28 June 2009 (UTC)

Calculating the magnetic force

between two magnet. it is not clear what μ ("mu") means, in the formula, and how to calculate this. if anyone can explain, and expand this subject. that would be great. thanks.

μ is just a constant. Similar to "G" in gravitation, and the only way to calculate this is to go this formula backwards. Measuring the force and using this formula to find μ. Is it clear? --Reza M. Namin (talk) 20:22, 16 October 2009 (UTC)

Section to be aded

You guys need a history section. There is no mention of magnets and their history on WP. hmmm.--Zereshk 09:58, 23 October 2005 (UTC)

My 4yo son wants to know 'How do they make magnets'?

So guys, how do they make magnets? Im assuming he's interested in the garden variety, solid stick things to your fridge variety. Thanks for any simple explainations..

Do you want to know how to take raw materials (like a ceramic powder) and turn them into a bar and then magnetize it, or do you just want to know how to take a material that isn't normally a magnet (like scissors) and then give it its own magnetic field? For a four year old, I'd go with the latter, the explanation is simpler and is probably what he's trying to ask. You can do an experiment with him (actually, you'll need to do it with him for safety) to turn something into a magnet: Buy a neodymium magnet (also known as a rare earth magnet). They're available from loads of online retailers and from some stores. Take the magnet and stick it to the metal part of the scissors close to the handle. Be very careful when you do this--rare earth magnets are extremely strong. Do not let your child play with them. Once you've got it stuck to the scissors, then have your son help you slide the magnet all the way down the scissors and all the way off. Then reattach the magnet close to the handle, have your son help you slide it off, and repeat this over and over. After like 20 or so slides down the magnet, you can use the scissors to pick up a single staple or something small like that.

An easy explanation could go something like this: Imagine you're running a comb through hair. As you run the comb through more and more times, all of the hairs get more and more lined up with each other, until all of the hairs are pointing in the same direction. You have to run the comb through the hair, and then take the comb out and go back to where you started, and then run it through again. In the scissors, there are lots of really tiny magnets all pointing in different directions. When you drag the big magnet along the length of the scissors, you're dragging all of the little magnets inside the scissors into rows. After a while, they're all pointed in the same direction (just like the hairs with the comb), so you've made all of the little magnets behave like one big magnet!Pkeck 05:28, 3 January 2006 (UTC)

Yes, that's a valid demonstration, but it's not really "how they make magnets". Unfortunately, the real process is not something you can easily do in your kitchen. Fridge magnets and the like are made from powdered ceramic material which is either sintered (welded by applying high pressure) into a rigid block, or embedded in flexible plastic. At this point, the object is not yet a magnet. It is then heated above its Curie temperature, placed inside the magnetic field of a much larger magnet, and cooled. When it is cold, it retains the magnetic field of the larger magnet. This is the adult version. I don't know what sort of words a four-year old boy understands, so I leave the translation up to you! --Heron 11:00, 18 February 2006 (UTC)

A simple version you could try: a big magnet it made up of tiny particles, and when aligned in the same direction, they form a magnet-you can do a demonstration with small bits of paper. have N and S on each end and show how they become aligned form scrambled. Ursper 20:13, 29 April 2007 (UTC)

Yes, I'd also like to see more information on how permanent magnets are made. For example:

• • What is the detailed manufacturing process for a magnet?
  • I heard that some magnetic materials are 'worked' as they cool to orient the grains?
  • Is the manufacturing process for rare earth magnets different?
  • What properties (of the BH curve) make a ferromagnetic material a good magnet?
  • How are the formulas for magnetic alloys determined? Is it a trial and error process?
  • Or is it possible to compute the magnetic properties of a material only from it's molecular structure, using QM?
  • Who invented common magnet materials such as Alnico and Alcomax? Rare earth magnets?
  • How long does the magnetism in a typical magnet last?
  • How much energy is contained in the magnetic field of a typical rare earth magnet?
  • Why are magnets often shaped like horseshoes?
  • Why does a 'keeper' help preserve the magnetism of a magnet?

--Chetvorno^TALK 08:53, 30 August 2008 (UTC)

I think some of these are excellent questions that need to be addressed in the article, especially the process of making a magnet, fundamentals of allowing it to harden (solidify or vitrify) under the influence of a field; interpretation of the B:H curve; the loss of magnetic saturation over time v. temperature (effect of thermal agitation and shock) and how the keeper increases the magnetic flux inside the magnet and reduces the tendency of the domains to randomize. This represents quite a bit of work (not to mention knowledge) to figure out how to articulate this. Anyone up to this? John (talk) 06:26, 11 September 2008 (UTC)

Far field of a magnet

The bit that says

At long distances, magnetic fields obey an inverse square law.

is incorrect. An electromagnetic wave will usually decrease by inverse square. So will the magnetic field of an isolated current element. An ordinary 'bar magnet', however, is usually modelled as a 'dipole element' in the far field (distances large compared with the separation of the poles). It becomes equivalent to an 'elemental current loop' whose far field is known to decrease with 1/ x³ -

http://www.netdenizen.com/emagnet/solenoids/ilooponaxis.htm

RAClarke 20:33, 9 January 2006 (UTC)

Calculating the magnetic force

Has anybody checked this "law" against a really reliable source like J. D. Jackson : " Classical Electrodynamics " , 3rd ed., (John Wiley & Sons, New York, 1998). I mean, I have studied physics now for quite a while and I never came across such a law.--LN2 02:43, 18 February 2006 (UTC)

I Love Magnets

LN2: With the units given it is definitely wrong. The general form is OK, and it could be made correct depending on how you quantitatively define "magnetic pole. For an alternate form of the law see

http://geophysics.ou.edu/solid_earth/notes/mag_basic/mag_basic.html

which seems to work out correctly.

In the form given, the numerator is Weber^2 = Tesla^2 x m^4. The denominator is (Tesla X m/Amp) X (m^2), so the result is Tesla x Amp x meter. Since a Tesla is a Volt-second, the result is Volt x Amp x second x meter = Watt x second x meter = Joule x meter which is definitely not a correct unit for force.

If no one disputes this I'm going to edit the main article in a week or so, to the form given in the link.

hfoltz, 18 March 2006

I agree: your version works out dimensionally, and mine doesn't, so mine must be wrong. It's interesting that both our references are from geophysics.ou.edu: mine from this page and yours from this one. It was unfortunate that I picked the wrong one. By the way, I reckon that since dipole moment is in A.m² [1] and is pole strength times distance, then pole strength must be in A.m. --Heron 14:04, 19 March 2006 (UTC)

Heron: I agree on the units of pole strength: A-m. That agrees with engineering texts such as Kraus. The geophysics.ou.edu website is interesting, from the format it's clear that the two pages were written by the same person. Again, I think it has to do with the unit system and either form could be correct. It's unfortunate that we've reached the 21st century and magnetic field units and terms still haven't been completely standardized. Hfoltz

Magnetising current (a la transformer)

Should we have a para on this here --- or not? --Light current 23:32, 3 April 2006 (UTC)

Geomagnetic Reversal

I previously requested a source on this, as I had simply never heard of it before, and the wording "it is known" seemed to beg citation. DMacks did an excellent job of providing a timely response, however, now I have a new concern. The article Geomagnetic reversal states that the last occurance was approximately 780,000 years ago. However, as there are multiple different consensii on the age of the earth (see Dating creation), some of which hold that the planet is under 10,000 years old, I felt the simplest solution would be to simply change "it is known" to "it is believed". I think this wording will avoid any controversy between parties who hold the different viewpoints. Any thoughts? Dansiman 05:42, 14 April 2006 (UTC)

There are multiple religious viewpoints about the age of the earth. However, the scientific consensus is clear: the earth is about 4.55 billion years old. IMO, a scientific article doesn't need to weaken itself to account for religious opinions, and especially those that aren't about the topic at hand (if there were religious opinions about geomagnetic reversal itself, that could be relevant here). Young-earth creationism is relevant to age-of-the-earth discussions, but doesn't need to be brought up every time someone mentions something that is "older that that".

I agree that "it is known" sounds strange (the whole point of Wikipedia is to write what is known). OTOH, I think "it is believed" isn't much better. Better to avoid weasel words altogether. To the best scientific understanding and evidence at this time, geomagnetic reversal has occurred, and we provide a link to a discussion of that evidence. If someone wanted to debate how to write about that evidence, the page about that evidence is the place to do it. DMacks 06:53, 14 April 2006 (UTC)

New edit by Heron looks good. Dansiman 05:46, 17 April 2006 (UTC)

add section on what happens if break a magnet into pieces?

I suggest add a section that explains what would happen if we break a magnet into pieces Rockvee 05:31, 3 May 2006 (UTC)

Check out the third paragraph here: http://en.wikipedia.org/wiki/Magnet#Permanent_magnets_and_dipoles Pkeck 19:39, 12 June 2006 (UTC)

history

I'd like to see a section on the history of magnets, I went to this article for that reason but there was no such section yet --213.118.83.229 08:53, 22 July 2006 (UTC)

Geographic vs Magnetic Poles

Geographic North and South are the terms given to the points on the earth's surface through which the axis of the earths rotation pass, ie points at 90 degrees lattitude, points furthest from the equator, the "top" and "bottom" of the world. The magnatic poles are some distance from these and drift about somewhat. Navigators have to correct for this, particularly when near the poles. The section on geographic vs magnetic poles that points out (rightly) that the north (magnetic) pole is actually a south pole uses the term "geographic pole" in a way different to this. A way I've never come across before--Mongreilf 20:24, 24 August 2006 (UTC)

I clarified that section. -- Beland 04:17, 1 April 2007 (UTC)

Online References Discussion

Hello,

This is an invitation to discuss the merits of the inclusion of links to content provided by commercial entities in the 'Online References' section of this article on magnets. The following links have been or are currently present in this article:

http://www.arnoldmagnetics.com/mtc/index.htm

http://www.magnetsales.com/Design/DesignG.htm

http://www.rare-earth-magnets.com/magnet_university/magnet_university.htm

http://oersted.com/magnetizing.PDF

http://www.consult-g2.com/

http://www.wondermagnet.com/magfaq.html

Each of these sites is primarily a site intended to convey information about the products or services of a company. In addition to their commercial content, each site has presented some valuable information related to Magnetics generally contained in a separate section or page of their site. Should these sites be included in this article under the section 'Online References' or should they all be excluded? Thanks for your input. —The preceding unsigned comment was added by 72.205.10.4 (talk)

As per extilink guidelines, if they have encyclopediac content that is not already present in wikipedia, a link from a wiki page a page of theirs that contains that content specifically relevant to the wiki page seems acceptible. The standard is for the section to be called "External links". DMacks 17:06, 14 December 2006 (UTC)

Based on current usage within Wikipedia, external links to information on commercial sites appear to be fairly common. If the content contains some valuable information not currently in Wikipedia, maybe it should be allowed as long as it does not obviously further some commercial interest. Public domain information should probably be incorporated into Wikipedia and the source references dropped if they become redundant. Zapala

The following is a comment by Mwanner about this subject that I thought should be included here:

"The best solution to the issue of these links is incorporate their contents (rewritten, of course) into the article, and then list them as sources or references. It's hard work, of course, but it results in our article becoming the best possible source of information on its topic; not incidentally, it also pays back the editor who does the work significantly-- after undertaking such a task, you will find that you know the subject much better than you did by just reading the sources."

Based on all these comments, I think that commercial information sources can be included as long as they are useful sources of information and not obviously promoting the products or services of the company. Once the external link is included an effort should be made to incorporate the useful content into the article and just reference the source. I started to incorporate some of the content into the article and invite anyone else to assist. The links are now in the External Links section of the article.

Magnetic force between two bar magnets

A formula to give an approximate value of the force between magnets would very useful, and is often asked for in discussion groups. The one given here does seem to have errors when you try putting in practical values for L, R, x. The force, I think, cannot exceed 2*B^2*A/u0 (at very small x), where B is the flux density of each magnet, but the formula has no such limit. The results did not agree with a finite element simulation using FEMM (often the disagreement was orders of magnitude). It's a pity because a working approximate formula would be invaluable for practical engineering, and I haven't been able to find another one on the net. --Gbeat 15:08, 26 December 2006 (UTC)

can extreme temperatures affect the strength of a magnet?

I'm working on a science fair project and need to learn if extreme temperatures would affect the strength of a magnet. What can you tell me regarding this question and what resources would you suggest I use to find out more?

Thanks for your help.

Walker Vaughn69.255.10.35 17:28, 27 January 2007 (UTC)

Hey man, I'm doing the same project. SWEET. Sorry though, I can't help.

Extreme heat certainly does; see Curie point and Néel temperature. -- Beland 03:56, 1 April 2007 (UTC)

Magnets in PC Software

Can anyone explain how Magnets in computer software work and if they are malicious? 89.243.2.232 18:59, 2 February 2007 (UTC)Chris mcCletchie

Magnetism is used in computer hardware, not software - software is just information. See magnetic storage. -- Beland 04:04, 1 April 2007 (UTC)

please explain me about the field direction for the eleptical and round magnets.i found that for elipse the direction is opposite (having two directional flow of fields from same point)[PROOF:try such magnet to show its north south direction just by rotating not reversing it shows opposite direction] were as in bar magnet its from north to south all around.--59.145.240.133 (talk) 05:39, 12 August 2008 (UTC)

Picture

Explain are permanent magnets really permanent Hey, props to whoever got the pic at the top of the article. —The preceding unsigned comment was added by 68.50.24.4 (talk) 01:15, 22 February 2007 (UTC).

'Permanent' is a matter of degree. The harder the material the more it resists the wear of time and temperature and mechanical shock, all of which tend to misalign the magnetic domains in permanent magnets and demagnetize them. On the other hand, when you want magnetic materials to demagnetize completely and immediately when the magnetizing current is turned off, they tend to be too slow and some residual magnetism too often hangs around. So there is no such thing as completely permanent or completely not, just a range. John (talk) 06:33, 11 September 2008 (UTC)

The two pictures are great, however, their relative left-right orientation seems reversed to me. By convention, the magnetic field lines of a permanent magnet loop from the North pole towards the South pole. It would be nice for the sake of symmetry, to have the pictures oriented in the same way, e.g. rotating the bottom picture of the solenoid by 180^oAndonee (talk) 02:32, 3 August 2009 (UTC)Andonee

Good work. I hadn't even noticed the little "N" and "S" letters in the top picture before now. :-) --Steve (talk) 14:40, 3 August 2009 (UTC)

Diagram requests

It would be useful to illustrate:

• How the different forms of magnetism arise from different atomic configurations.
• How N-S orientation aligns with the Earth's geography.
• How electric currents, electric fields, and magnetic fields are oriented in electromagnets.
• How magnetization can work.

-- Beland 04:01, 1 April 2007 (UTC)

For #1, there are some diagrams of this already in the article. Which ones do you still want?

For #2, there are these:

• File:CampoMagnetico.png
• 

What do you mean "How magnetisation can work"? pfctdayelise (talk) 13:53, 29 July 2008 (UTC)

I believe that, like the 4 year old above, many people are curious about what "magnetism" really is, but express that curiosity in terms of "how do they make magnets." I know, I was a 4 year old once. Unfortunately, the answer is not simple, the real answer involves Special relativity. Rats!! John (talk) 06:40, 11 September 2008 (UTC)

Non Acctracio

What is non acctractio It was in a magnet website and if it is real then someone should add what it is. (Ponser 20:12, 7 May 2007 (UTC))

The Measuring Magnetic Properties section needs to be moved/changed

It should not be the first section in the article (besides the intro), and it should not be an FAQ.

See WP:NOT#info. atomicthumbs 04:16, 8 June 2007 (UTC)

Expanded 'Magnetic forces' and renamed to 'Magnetic behaviors'

I rewrote the 'magnetic forces' section to make it a little more fun to read. I'd like my facts to be checked - they were mostly borrowed from the main articles specified and some of my own knowledge. Also, looking for consensus to remove the tag for expansion.

--OEP 21:26, 25 June 2007 (UTC)

Possible vandalism

In the Idiot article I reverted a vandalism by user Nal101 that said: "In the real world, Jeff Cutuli and Jeff Snyder are considered idiots because they think that the Playstation 2 doesn't have magnets in the door."

The only other colaboration by this user is in this article, where he added this text: "Most notably, magnets have been used in virtually every piece of electronic equipment over the last 20 years, especially in devices that have rotational characteristics (I.E. cd/dvd player doors/trays). The magnet secures the door in place until it is de-magnetized (allowing the door/tray to open). Contrary to popular belief, magnets pose no harm to these devices."

Now, this doesn't look like vandalism at first glance, and since I don't know anything on the subject, I will just add a "citation needed". But please, someone could check this out? --PeterCantropus 23:26, 29 July 2007 (UTC)

I just got a bit WP:BOLD and nuked it. There was too much over-generalization:

• virtually every piece of electronic equipment? That's a lot of cell-phone magnets!
• DVD players etc? They're just as hard to open when unplugged, so it's not as simple as de-energizing some interlock.
• Uncited assumption of "popular belief".

DMacks 15:00, 30 July 2007 (UTC)

Magnetic moment

The articles says magnetic moment is inversely proportional to the cube of distance. However in the same paragraph it gives a formula for magnetic moment as A·m². Dimensional analysis on this formula indicates magnetic moment is inversely propotional to the squre of distance. I realize from reading above that both statemens may be true, at different scales. If this is the case there needs to be a qualifier so that that there is no contradiction. I am fascinated by why the inverse square law is not applicable for the first statement and would love to undestand this better - so fleshing it out wood be great

Rmaytham 12:22, 15 September 2007 (UTC)

Differenciating N & S

If I've got a magnet, how do I determine the north pole & the south pole of it? I guess a compass would be one way, but is there another way? -Joshua Hrouda

Joshua, Yes, the section of the article called: "North-south pole designation and the Earth's magnetic field" explains how to suspend a magnet so its North pole points North. Was that clear? John 19:05, 24 October 2007 (UTC)

Hall effect sensor

I've heard that a Hall effect sensor can sense whether a N field or S field is near it, and give an output accordingly. If so, then how is it done? -Joshua Hrouda

Yes, the hall effect sensor is a small chip in a probe, and you just hold the probe near the pole of the magnet and read its polarity and strength off the meter. John 19:07, 24 October 2007 (UTC)

Why when... ...?

-Why when I broke a stick magnet that i had, did one side reverse polarity?

To illustrate this effect:

+ ======= -

+ ==== - \break\ - ==== +

^ where the magnet fits together, the ends repel each other.

This is counter-intuitive because it implies that one and only one side of the magnet switched polarity.

i experimented more and the same thing happened over and over again.

i did not figure out if the larger or smaller side switched, so that information is currently unknown to me.

WHY DOES THIS HAPPEN? what is magnetism?

- BriEnBest (talk) 12:03, 22 November 2007 (UTC)

oh and btw how do i get rid of the dotted outlines? BriEnBest (talk) 12:04, 22 November 2007 (UTC)

graphite diamagnetic?

The article states that graphite is diamagnetic, but one can observe an attraction between a piece of pencil lead and a neodymium magnet. If it was diamagnetic, wouldn't that mean it would be repelled? Or could this be due to ferromagnetic contamination in the graphite?--207.233.88.250 (talk) 05:02, 7 December 2007 (UTC)

Yes, it's commonly contaminated with iron.- (User) WolfKeeper (Talk) 19:20, 4 April 2008 (UTC)

magnets

who made magnets and where was he born —Preceding unsigned comment added by 168.11.16.2 (talk) 19:08, 12 February 2008 (UTC)

Magnet and iorn expiriment(Iorn Meets Magnet and Sticks to it)to make magnetic field lines

To show the relationshp between iorn magnet do the followinbg expiriment. You will need the following : a white sheet of computer paper iorn (2 hand fulls) north and south pole magnet 1:cover themagnet with computer paper 2:sprinkle on the iorn 3:slide paper back and forth When you see curved lines spreading diffrent ways those are the magnetic field lines —Preceding unsigned comment added by 207.203.80.27 (talk) 17:44, 8 March 2008 (UTC)

I think you mean iron ;-)- (User) WolfKeeper (Talk) 19:19, 4 April 2008 (UTC)

uses of magnet

what is a magnet use for —Preceding unsigned comment added by 209.94.220.183 (talk) 08:55, 14 April 2008 (UTC)

Quantum Magnets

I consider interesting people in physics write an article about Quantum Magnets, and at the bottom of this article could be found a link redirecting to the Quantum Magnet article. —Preceding unsigned comment added by 79.145.78.9 (talk) 03:35, 3 May 2008 (UTC)

where is the pull of the magnet the strongest

The pull is strongest near the poles. The closer to the pole, the stronger the pull. John (talk) 05:17, 27 September 2008 (UTC)

Possible bad info on Magnet#Force between two magnetic poles

“ The force between two magnetic poles is given by:

$F={{\mu q_{m1}q_{m2}} \over {4\pi r^{2}}}$ [2]

where

F is force (SI unit: newton)

q_m1 and q_m2 are the magnitudes of magnetic poles (SI unit: weber or volt sec)

μ is the permeability of the intervening medium (SI unit: tesla meter per ampere, henry per meter or newton per ampere squared)

r is the separation (SI unit: meter).

The pole description is useful to practicing magneticians who design real-world magnets, but real magnets have a pole distribution more complex than a single north and south. Therefore, implementation of the pole idea is not simple. In some cases, one of the more complex formulae given below will be more useful.

”

By just looking at the units, I see something wrong immediately.

For example, it's obvious that the left hand side of the equation is supposed to be in units of force. The right hand side of the equation doesn't match up however. Look what happens when the dimensions are compared.

$Newtons={\frac {{\frac {Newtons}{Ampere^{2}}}Volts^{2}*seconds^{2}}{4\pi *meters^{2}}}$

$1={\frac {{\frac {1}{Ampere^{2}}}Volts^{2}*seconds^{2}}{4\pi *meters^{2}}}$

$4\pi *meters^{2}={\frac {Volts^{2}*seconds^{2}}{Ampere^{2}}}$

$4\pi *meters^{2}=Ohms^{2}*seconds^{2}$

$4\pi *{\frac {meters^{2}}{seconds^{2}}}=Ohms^{2}$

See the problem? (Hint: You don't think ohms is simply a subtraction of the charges' velocity do you?, and you don't think that because force * distance/time is power... that current is the square root of force, do you?, or that force^2 is the same as current?, or that voltage is velocity/force?) Here's another way to show what's definitely wrong with it.

$Newtons={\frac {{\frac {Telsas*meters}{Ampere}}\left(Webers\right)^{2}}{4\pi *meters^{2}}}$

$Newtons*meters={\frac {{\frac {Telsas*meters^{2}}{Ampere}}\left(Webers\right)^{2}}{4\pi *meters^{2}}}$

$Joules={\frac {Telsas*Webers^{2}}{4\pi *Amperes}}$

$Joules={\frac {Telsas*Volts*Seconds*Webers}{4\pi *Amperes}}$

$Watts={\frac {Telsas*Volts*Webers}{4\pi *Amperes}}$

$Watts={\frac {Telsas*Ohms*Webers}{4\pi }}$

$Amps^{2}={\frac {Telsas*Webers}{4\pi }}$

According to Google (http://www.google.com/search?q=1+weber+*+1+tesla), units of Teslas times units of Webers are supposed be in units of:

m^2 kg^2 s^-4 A^-2

But if "m^2 kg^2 s^-4 A^-2" was the same as "A^2" then:

A^2 = m^2 kg^2 s^-4 A^-2

A^4 s^4 = m^2 kg^2

A^2 s^2 = m kg

And since A*s is coulombs, then:

kg = C^2/m ... wtf?

Looking back at the previous example, we had:

$4\pi *meters^{2}={\frac {Volts^{2}*Seconds^{2}}{Ampere^{2}}}$

If you simple did the dimensions as made obvious in ohm's law, then:

$4\pi *meters^{2}=Ohm^{2}*seconds^{2}$

$sqrt(4\pi )*meters=Ohm*seconds$

$sqrt(4\pi )*meters=1henry$

It's soo wrong, yet check out what happens when you do the following:

$Newtons={\frac {{\frac {Newtons}{Ampere^{2}}}Unknowndimension^{2}}{4\pi *meters^{2}}}$

$1={\frac {{\frac {1}{Ampere^{2}}}Unknowndimension^{2}}{4\pi *meters^{2}}}$

$4\pi *meters^{2}={\frac {1}{Ampere^{2}}}Unknowndimension^{2}$ :$4\pi *meters^{2}*Ampere^{2}=Unknowndimension^{2}$

So technically, the unknown dimension is supposed to be dimensions of electrical current times distance, yet the description says it is volt*seconds or webers. Are you telling me if you just take the current times distance and divide by time that you'll get voltage. Fine, I'll admit it makes intuitive sense:

The more voltage, the large the gap you can cross.

The more voltage, the quicker the charges will want to drain from the batteries.

However, if current * distance was webers (magnetic flux), when webers are actually in units of m kg s^-2 A^-1, then kg m s^-2 would be the same as A^2... the same problem we found earlier! Does twice the current really truly mean that the forces are going to be four times as great? Forces on WHAT?

If this is the correct formula, then I am genuinely shocked and dismayed (although may feel vastly superior to) than scientists, especially physicists today, even of those outside my own country (America), who can't see a blantant error (or shall we say, great discovery? =P), that someone who took one semester of University level physics and one semester of Cosmology (who majors in ACCOUNTING) can see due to the slightest bit of patience with what is generally supposed to be basic electromagnetic theory?Kmarinas86 ^(6sin8karma) 17:30, 10 August 2008 (UTC)

Good work. I changed the unit specification.

There are actually two units for "magnetic charge" that are in use (amp*meter and weber), which differ by a factor of mu_0. The formula there is for amp*meter, as you point out, but I guess someone added in the other unit without checking. --Steve (talk) 18:02, 10 August 2008 (UTC)

It makes no sense to keep the equations using the monopole concept if there are solutions given using the correct expressions. See Magnet#Force_between_two_cylindrical_magnets with a reference published and validated in 2009. Also see Magnetic_moment#Effects_of_an_external magnetic_field_on_a_magnetic_moment and the reference there for a discussion on why is not good to use the electrical analogy. --User:Kakila , 17 February 2009 —Preceding undated comment added 08:56, 17 February 2010 (UTC).

How does magnet attract metal?????

Hi Wkipedia I'm one of your members. And I want to ask you if you can show me how magnet attracts metal in the page. I'll be waiting!!

Thanks —Preceding unsigned comment added by Anthony-2012 (talk • contribs) 09:07, 21 September 2008 (UTC)

Alignment of magnetic domains.Kmarinas86 ^(6sin8karma) 10:55, 21 September 2008 (UTC)

Anthony, that is a really good question, and I apologize but I am not going to try to answer it here. I think this should be addressed in the article; it goes straight to the heart of what a magnet is; what it does, but it is very involved to provide a satisfying explanation. I am not sure how basic to make the explanation. First, we need to explain where the fundamental force of a magnet comes from, which is from electrically charged particles (electrons, protons). I don't really know why charged particles exert a force on each other. Then show how the motion in atoms disturbs the charge balance, giving rise to that force. This involves special relativity. Then show how a magnet affects the alignment of atoms in a magnetic material in a way that causes this force. Really explaining any one of these steps could be an article and somewhat overwhelming. But I bet many people come to this article looking for an understandable explanation. It will take someone really smart to articulate a simple AND satisfying answer. John (talk) 05:11, 27 September 2008 (UTC)

I was bothered by the same problem Anthony was - the article has a description of how ferromagnetic materials become magnetized, but not how they attract metal. The short answer is as Kmarinas86 said: alignment of magnetic domains. When a piece of iron comes near a magnet, the magnetic field of the magnet aligns the magnetic domains of the iron, so it becomes a magnet temporarily while the magnetic field is present. The direction of the magnetic field induced in the iron is such that the two magnets have opposite poles nearest one another, so they attract. --Chetvorno^TALK 21:58, 4 December 2008 (UTC)

MKS units

There were two MKS systems, the rationalized and the un-rationalized. The SI system used the rationalized system. The un-rationalized system used U₀=10^-7. reference Dawes electrical engineering edition 4 page 221 —Preceding unsigned comment added by 203.47.38.170 (talk) 05:41, 18 December 2008 (UTC)

how to make a magnet

hey people- im in the 6th grade and in the science fair anyone know how to make a magnet???? i am gonna try making a magnet then proving points of the north and south poles of it. any help???? —Preceding unsigned comment added by 76.112.80.95 (talk) 23:28, 10 February 2009 (UTC)

• Reposted to Wikipedia:Reference desk/Science#how to make a magnet. - Eldereft (cont.) 05:09, 11 February 2009 (UTC)

Your question is more appropriate for another section of Wikipedia, called Wikipedia:Reference desk/Science#how to make a magnet but science fair questions are not allowed there. You will get better answers if you follow that link. However, I will give you a hint: You can make a magnet from a plain nail if you stick the nail to some other very strong magnet. I will also be happy to provide more details if you ask your question on my talk page in the following link. Good luck. John (talk) 00:33, 12 February 2009 (UTC)

Question about Magnet

Please is it possible to get magnet circular shape as big as 5ft wide and 8in thick. Meanwhile it must be very light cos I want if for a project which will be lifted up with balloons. However what should be the distant between two magnets if one will be at a point and the other will be on the other end pulling each other? I refer to the sized mention above. —Preceding unsigned comment added by Stuntprojects (talk • contribs) 10:39, 24 April 2009 (UTC)

Print problem

On these library computers, this page (Magnet:article) experiences a print problem under firefox, but not internet explorer: Firefox prints a page with the citation header/footer, but nothing else. (Writing from the mall-library branch of Prescott Public library, Prescott, AZ, USA)72.24.124.24 (talk) 18:31, 28 April 2009 (UTC)

Alert to fact that I will soon move most of Physics of magnetic materials section from this article to Magnetism

To me magnets describe objects that produce a noticeable magnetic field. Magnetism is about the phenomenon and the material. TStein (talk) 06:27, 28 May 2009 (UTC)

I agree, glad someone is cleaning up this messy article. To throw my two cents in, I think the material on paramagnetism and diamagnetism should certainly go, as it has little relevance. There should still be a basic explanation of ferri- and ferromagnetism since those are the mechanisms of permanent magnets. I feel the definitions of magnetization and dipole moment should stay, and I'd like to see some explanation of the Ampere and Gilbert models remain, since those are the models used to analyse magnets. --Chetvorno^TALK 07:19, 28 May 2009 (UTC)

Sounds good to me. (Is that 'great minds think alike' or 'fools seldom differ'). I don't know how much I can do. I have already bitten off more then I can chew. I will do what I can soon, though. Plus, wikipedia is worse then surfing the web for me. One problem with one article leads to another article...) TStein (talk) 08:28, 28 May 2009 (UTC)

I finally got a chance to move the material

I finally got a chance to move the material that I suggested. I also moved some material around as well. Please let me know, here, how it looks.

There is still a lot of stuff that needs to be done. I liked most of Chetvorno suggestions that I did not implement; I don't think I have the time to do them now, though. I also don't like the way the first 'physics of' section is structured; it has too much detail that is not needed for the rest of the article front loaded. If I had the time to figure out a better way to organize it I would. Unfortunately, there is just too much that needs doing in wikipedia physics articles in general that I only have enough time for the most egregious stuff. TStein (talk) 21:21, 3 June 2009 (UTC)

time for a summary and consistency in articles

I was about to design an electromagnet and, thinking I could simply jump on Wiki and get the info I needed, found no less than 21! articles on magnetism plus another 20! or so on related matters (there are more!). I'm good at research but jumping from link to link was doing my head in so I began a Summary on Magnetism. I have spent every waking hour of this week writing, researching, thinking and more thinking. I now have an intuitive feel for the subject but it was extremely difficult and quite confusing. I think there needs to be more consistency accross articles (units, symbols) whithout repitition, many more diagrams and a more intuitive structure. But especially, basic concepts should be thouroughly explained while keeping it brief, leaving out some of the more whimsicle topics (ie earths magnetic field) and putting others in an appendix (such as history, people). I guess ultimatly, one should be able to put ones research into practical use whthin hours, rather than weeks. What I would like to see is a complete overhaul of the entire subject of magnetism, and a summary article that ties the whole subject together (like my summary) for those who just want an intuitive and practical understanding whithout the hair loss. P.Taylor Q5101997 (talk) 00:16, 1 November 2009 (UTC)

heavy magnet

to stunt projects a magnet 5ft accross and 8 inches deep would weigh about 3tonnes. dont drop it on your foot, and dont go near it if you have had metal put in you for some medical reason —Preceding unsigned comment added by 123.211.94.229 (talk) 04:09, 1 November 2009 (UTC)

temporarily de-magnetize permanent magnet by running a current through it?

I read somewhere that one could temporarily de-magnetize a permanent magnet by running a current through it.

Frustrated after finding nothing about it in a quick search, I tried some original research.

I touched a strong little horseshoe-shaped iron magnet to the poles of a 9-volt battery (magnet's poles were exactly the same distance apart as the battery's). Magnet latched on strongly, Got a spark, so plenty of current was going through the magnet. But magnet seemed about just as strong as when it attaches to the fridge. Maybe just a little weaker, not much.

If anyone has seen this as another means to de-mangnetize temporarily, please say so. —Preceding unsigned comment added by 66.167.61.90 (talk) 02:09, 11 January 2010 (UTC)

Pull force with and without steel

I was reading the K&J Magnetics FAQ page which has a description of three use cases for which they provide measured holding forces. (1) The force to pull the magnet off a semi-infinite steel flat. (2) The force to separate two semi-infinite steel flats held together by the magnet. (3) The force to separate two identical magnets. Interestingly, their calculator (which is apparently based on emperical experiments, not theoretical results) indicates that case (2) is far and away the highest force.

To me, the most obvious question for those new to magnets is "how do I make them pull harder"? I've been scouring Wikipedia for a better understanding of this. Two interesting findings are the Halbach array found in refrigerator magnets and the magnetic base, which I'd always wondered about. With these things in mind, it seems like case 2 has the strongest holding force because the magnetic circuit formed with two pieces of steel has field lines that radiate out through the steel away from the magnet and through the air gap.

A few questions:

1. If the steel in cases 2 were changed to electrical steel, would the force increase?
2. If the steel flats wraped around the magnet in case 2 so that the planes almost touched, would that change (increase?) the force?
3. Given field lines, how would one compute force, in theory? It's not clear from this article. I realize it involves the solutions to nasty nonlinear differential equations with weird boundary conditions, but I haven't found an equation that gives me any intuition for it... My sense is that force comes from lengthening field lines?), but that longer field lines have lower flux density, corresponding to pull force getting weaker as magnets are separated... It seems like it must just be the partial derivative of magnetic energy with respect to pulling the pieces apaprt...

How does one get a useful intution for this stuff? Thanks. —Ben FrantzDale (talk) 14:26, 12 January 2010 (UTC)

Good questions; this stuff should be in the article. Your ideas are correct. The force due to a uniform field through a cross sectional area A, such as would be exerted by the pole piece of a magnet with area A lifting a block of steel, is

$F={\frac {B^{2}A}{2\mu _{0}}}\,$

If the field is nonuniform the force must be found by integrating this, but in the situations you mentioned, where there is a magnetic circuit of ferromagnetic core material, the field will be approximately uniform across any cross section of the core. --Chetvorno^TALK 18:10, 12 January 2010 (UTC)

I'm trying to understand what seems like a nonlinear effect -- adding a second steel plate seems naively like it should "dilute" the strength, or at best do nothing. I would guess that the second piece of steel effectively makes more aria for which B is greater, thereby increasing

$F=\int _{A}{\frac {B^{2}}{2\mu _{0}}}\,dA$.

Does that sound right? —Ben FrantzDale (talk) 21:19, 13 January 2010 (UTC)

Common magnet composition

By dissolving a common magnet in hydrochloric acid, some of the metals it contains can be found out. I dissolved a common cheap magnet (the type they use in shower curtains) in HCl. The first color noticeable was the yellow color of iron chloride, formed by the reaction of the iron in the magnet with the hydrochloric acid. The next color noticeable was the red color of cobalt chloride, formed by the reaction of cobalt in the magnet with the hydrochloric acid.--98.221.179.18 (talk) 21:23, 19 February 2010 (UTC)

Sounds like your magnet was alnico, an iron alloy with aluminum, nickel, and cobalt. It has up to 24% cobalt. --Chetvorno^TALK 17:52, 12 March 2010 (UTC)