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Author Topic: Magnets  (Read 6861 times)

Offline tony6789

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Magnets
« on: 17/02/2006 14:29:51 »
how do magnets work?

- Big T


 

another_someone

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Re: Magnets
« Reply #1 on: 17/02/2006 16:35:20 »
Are you asking what is magnetism?

Are you asking how materials become magnetised?

Are you asking how are magnetic fields created?

Are you asking why magnets attract or repel other magnets, and why they attract otherwise unmagnetised ferromagnetic metals?
 

Offline Ray hinton

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Re: Magnets
« Reply #2 on: 19/02/2006 01:46:49 »
no,he asked how magnets work,simple enough question.[?]

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Offline ukmicky

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Re: Magnets
« Reply #3 on: 19/02/2006 02:13:13 »
quote:
no,he asked how magnets work,simple enough question.


Yes he was being rather pedantic wasn't he,   Maybe he doesnt know the answer ;):)

Michael
 

Offline Ray hinton

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Re: Magnets
« Reply #4 on: 19/02/2006 02:28:35 »
everyone knows that they suck at one end and blow at the other,its just so simple.:D:D:D

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Offline neilep

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Re: Magnets
« Reply #5 on: 19/02/2006 03:26:46 »
quote:
Originally posted by Ray hinton

everyone knows that they suck at one end and blow at the other,its just so simple.:D:D:D

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..isn't that what a snake does ? :D

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Offline tony6789

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Re: Magnets
« Reply #6 on: 22/02/2006 14:16:11 »
Yeah simple but how does it really work

- Big T
 

Offline Solvay_1927

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Re: Magnets
« Reply #7 on: 22/02/2006 22:29:31 »
Tony,
er, at the risk of sounding patronising ... have you tried doing a google with the phrase "how do magnets work"?  You might find that that gives you lots of useful explanations.

("Patronising" - that means "talking down to people", by the way ;))
 

Offline Dr B

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Re: Magnets
« Reply #8 on: 24/02/2006 13:04:02 »
Where does a magnetic field come from - a moving charge.  Electrons orbiting atoms produce magnetic fields.  Why do moving charges generate magnetic fields - change the subject.  What is charge, where does that property come from.... Not sure google will give you an "answer"

Dr B
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another_someone

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Re: Magnets
« Reply #9 on: 24/02/2006 13:16:28 »
quote:
Originally posted by Dr B

Where does a magnetic field come from - a moving charge.  Electrons orbiting atoms produce magnetic fields.  Why do moving charges generate magnetic fields - change the subject.  What is charge, where does that property come from.... Not sure google will give you an "answer"

Dr B
Istanbul



The moving charge bit, according to Einstein, was a consequence of general relativity (move an electron at close to the speed of light, and it's relativistic distance will get closer, and so its electrical charge will be stronger, than if the same electron were stationary (at least, that's as far as my small brain can understand it).

Where does charge come from seems as much of a question as where does energy come from it seems to be a basic and irreducible attribute of the universe.



George
 

Offline Ray hinton

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Re: Magnets
« Reply #10 on: 24/02/2006 19:44:18 »
tony try here,www.pa.msu.edu/~sciencet/ask_st/050593.html - 3k
 

Offline heikki

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Re: Magnets
« Reply #11 on: 28/02/2006 06:32:49 »
.
« Last Edit: 07/03/2006 06:17:40 by heikki »
 

Offline cuso4

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Re: Magnets
« Reply #12 on: 28/02/2006 11:41:03 »
Essentially, there are three types of magetism:

1. Ferromagnetism eg permanent magnets. This is where all the magnetic moments align in the same direction (this is how you get north pole and south pole). The strongest magnet known is a neodymium-iron-boron compound (Nd2Fe14B), which is used in earphones and high-performance speakers.

2. Anti-ferromagnetism - magnetic moments align in opposite directions and cancel leaving no net moments.

3. Ferrimagnetism - moments align in opposite directions leaving net residual moment. There is a family of compound called rare earth garnets (Ln3Fe5O12), a complex oxide. Its ferrimagnetic properties have unsual temperature dependence.

Let's say the lanthanide has bigger moments and is pointing up; and the iron has smaller moments pointing in opposite direction. This results in a net magnetic moment pointing up. However, as you heat the compound, the lanthanide magnetic moment is destroyed leaving only the iron's magnetic moment which is pointing in a different direction. So the overall effect is a change of direction of magnetic moment on heating the compound.

Personally, I find this quite fascinating.

Angel
 

Offline Atomic-S

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Re: Magnets
« Reply #13 on: 01/03/2006 04:51:08 »
quote:
Yeah simple but how does it really work

To really delve into the deep questions about magnetism gets a person into some deep quicksand, because electromagnetism is a very basic phenomenon in nature, more basic than the existence of the atom itself, and one cannot approach to this level without getting mired in quantum mechanics, and even then science does not possess all the answers. Associated with this question is also the question, exactly how does gravity work? And a few other basic questions concerning the most basic nature of nature. Scientists currently are seeking a Grand Unified Theory to tie this all together but thus far has nothing solid.

A partial understanding of magnetism of course involves the frequently repeated observation that it occurs when charge moves. It is a variant of the phenomenon of the electrical attraction or repulsion of charge. Charge itself is believed to occur due to the emission and resorbtion of photons by charged particles, a process whicn I do not know that anyone has explaned. But the transfer of these particles between charged bodies involves a momentum change (much like the recoil of a rifle when fired, and the jumping of the target when struck), which deflects the course of the particles, and results in what we observe as repulsion -- only in the case of things subatomic, it can also result in attraction, because the ruls under which this process take place are quantum mechanical, not classical. The force resulting has definite directional properties, as you know. This directionality appears to be intimately connected with the fact that all photons spin with an angular momentum h.  The spin wave function thus has a positive and negative direction, because a circular function that repeats itslef in one complete revolution of a circle will undergo one complete cycle from positive and negative in one revolution. This seems to account for electrostatic behavioor.  Additionally, because quantum mechanical wave functions are generally complex numbers, not just real numbers, the circular wave function also has an i and -i direction, at right angles to the positive and negative directions. These appear to correspond to the north and south magnetic directions.

When the charged body is in motion, both it and its field of emitted or resorbed photons enter a different reference frame, according to Einstein's theory of relativity. This affects the way the photons appear to the observer, resulting in, among other things, the manifestation of electrostatic or magnetic properties of the field differently: if one or the other of these was absent in the o riginal reference frame, they will in general be visible in another reference frame. Tjhus, a charged particle which when  viewed at rest has only electrostatic characteristcs, will, when viewed in motion, be seen to also be surrounded by magnetic characteristics (lines of force) circling it at right angles to the directions of the electrostatic force and also to the direction of motion. The new reference frame also has one other significant effect: Due to the Lorentz contraction, the field is squashed in the direction of the object's motion, resulting in the field being weaker both in that direction and the opposite direction, but stronger at right angles. In conductors carrying currents, this effect means that from the viewpoint of moving charge in either conductor, the equal but opposite charges in the opposing conductor no longer look alike, but the stationary (opposite) charges now appear stronger, being viewed at right angles to the direction of motion. The result is that the moving electrons in the one conductor are attracted to the protons in the other conductor, insofar as they are no longer effectually neutralized due to the distortion of the fields. So the wires attract. Or, when viewed in the ground frame, the fields of the moving electrons no longer exactly counterbalance those fo the stationary protons, in that the former now has magnetic lines also due to the motion, and these are observed as magnetic force.

The magnetic force emitted by a piece of magnetized iron is due, not to electrons in orbits primarily, but due to another motion: All electrons spin with an angular momentum 1/2 h, and this is equivalent to a wire loop carrying a current. In ferromagnetic materials, something about the crystal structure and the permissible energy states which the electrons may occupy, causes certain electrons to alighn in the same direction, so that their collective magnetic fields appear on the outside. This alignment however ordinarily occurs within individual small zones in the metal, which collectivey are randomly oriented so that no externally effective field is seen. When, however, the metal is magnetized, the crystal structure is rearranged in such a way that more atoms attach themselves to zones aligned in a certain direction, resulting in a net overall magnetization of the entire piece. If the metal is of a magnetically "hard" composition, once the magnetization has been accomplished, it remains "permanently" -- is difficult to remove. In other metals having magnetically "soft" compositons, as soon as the magnetizing force is removed, most of the atoms revert back to the previous alignment of random zones, and the overall magnetization is lost.
 

Offline tony6789

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Re: Magnets
« Reply #14 on: 02/03/2006 14:25:52 »
thks my peps

- Big T
 

Offline Sandwalker

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Re: Magnets
« Reply #15 on: 13/03/2006 08:32:36 »
And there was me thinking it may be snakes all the way down.

But it could be the effect of one or more of those hidden dimensions they keep on talking about in M-theory!

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Offline chris

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Re: Magnets
« Reply #16 on: 24/03/2006 08:38:24 »
quote:
Originally posted by Solvay_1927

Tony,
er, at the risk of sounding patronising ... have you tried doing a google with the phrase "how do magnets work"?  You might find that that gives you lots of useful explanations.

("Patronising" - that means "talking down to people", by the way ;))



This is not directed at anyone in particular, but this is a good opportunity to make an important point about this forum.

Recently there have been a number of replies to posts along the lines of "why don't you go and look for yourself?"

Please don't answer people like this. Often these are good questions, and the whole purpose of this forum is to grow a stock of information to which we have all contributed, and which has been checked for validity.

If you refer someone to FOFO (F off and Find Out), you've no guarantee that they won't stumble into some random site containing incorrect information.

Worse still we've lost a contributor, and we've lost the information and content that they might have added subsequently. This is not how you grow an information resource or online community.

So, and this goes for the whole forum, when someone asks a question, please endeavour to help by providing useful information, or desist from replying to them. It's also a great way to improve our own personal knowledge, and highlight strong and weak web-resources.


Thanks for being understanding,

Chris

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Re: Magnets
« Reply #16 on: 24/03/2006 08:38:24 »

 

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