magnet

[TheGeek]

Hi,

I would like to know more about magnets. How do they work?

 

One other question i had was is everything attracted to mangets? (if they were strong enough) There is protons and electrons in a wood atom but why doesn't a magnet attract/repeal that?

 

basically, i want to know all about magnets. Tell me it in highschool/ freshman at college level knowledge.

[labview1958]

I also have a problem with magnet's. Let's say the repulsive force between two identical magnets is 0.2N. The attractive force would be maybe -0.3N. Why not -0.2N? Why not the same value?

[JustStuit]

It works with unpaired electrons in an atom which has charge. In wood, the atoms are neutral and have no attraction.

[JustStuit]

Unpaired electron spins, combined with molecular structure. That's why relatively few materials are - electron spins tend to pair up, spin up + spin down, leaving no net magnetic field for the atoms.

Quote from Swansont in thread http://www.scienceforums.net/forums/showthread.php?t=18008.

 

Read through that.

[TheGeek]

i heard that if you get a magnet that's really...really strong that it will attract wood.

[JustStuit]

I don't see why. Maybe because of the position of the atom not always being perfectly stable it would have a slight charge imbalance. But I don't see this being enough for a magnet to attract wood. Maybe some1 with knowledge of this would care to post.

[Edtharan]

really strong that it will attract wood.

AFAIK: It would because the electrons with spins that create an attractive force would be forced closer to the pole and the electrons with spins that create a repulsive force would be repelled (creating a skewed distrabution of the electron orbitals around the atom). The magnet would have to be very strong and I am not sure that any material could handle that field strength without flying apart from it's own magnetic repulsion.

[EverCurious]

So, in theory, any magnet of that strength would not be able to exist due to its own properties? Do you have the mathematical formulas and equations for this? I'm just curious as I have a very basic knowledge of magnetism myself.

[labview1958]

Why is the attractive force between identical magnets more then the repulsive force?

[gcol]

Magnetic wood

 

Wood, as nature grows it, is not pure cellulose. It contains mineral impurities. Some of these impurities may have magnetic properties. Irrespective of the intrinsic hardness of the wood, these minerals can blunt sawblades rather quickly. A really strong magnet may attract these minerals, thus drawing the wood with them.

 

I would be surprised if attraction really is stronger than repulsion. It is relatively easy to measure attraction using a simple spring balance, where the maximum attraction is at the point where the magnets are in physical contact. Much more difficult to measure pushing resistance, and to stop at exactly the point where the surfaces just meet, so that physical force does not add to magnetic force.

 

Just ideas, I'm no expert.

[labview1958]

I am 100% sure that attraction is stronger then repulsion. The question is why?

[swansont]

I am 100% sure that attraction is stronger then repulsion.

 

 

How are you sure of this?

[gcol]

Botheration. I'm curious now.

I have found a statement in relation to the theory of DC motors that said repulsion was marginally stronger than attraction. A statement during a laymans explanation of magnetism that said attraction and repulsion had the same force, and an explanation at quantum level that seemed to say that at "normal" distances they were equal, but at "atomic" distances things were not so simple.

 

Expert help required, please.

[swansont]

Part of the problem might be context that is missing, but if attraction is stronger than repulsion, one could envision the possibility of doing work with this. Since in a closed loop, you now have the possibility of having done more work with the attraction than with the repulsion, this would be the creation of energy in violation of the first law of thermodynamics. So I'm wondering what could be missing from the very general statement "attraction is stronger then repulsion" that closes the loophole, as it were.

[gcol]

Much obliged. Will ferret around some more. Dont hold your breath.....

[labview1958]

Attraction is stronger than repulsion. See this:

 

http://www.magnetsales.com

 

See the page on push and pull calculation.

[JustStuit]

It may be right, but don't trust sites that aren't respectable or trying to sell you something. They've been known to lie. I actually couldn't find the push pull page so I don't know about it.

[labview1958]

Click magnet design and then calculation tool kit.

[swansont]

Click magnet design and then calculation tool kit.

 

Agian, no context. They don't show you what they're calculationg, or how they are doing it.

 

The basic force equation is [math]{m_1 m_2}/\mu r^2[/math], so flipping the magnet should just give you a change in sign, that is, if the magnetic moment is symmetric. But that's dependent on the geometry of the magnet; I don't think your contention is generally true.

[gcol]

Having said, post #10, that I would be surprised if Attraction (A) and repulsion ® were unequal, I am now not so sure. Because:

 

1. Throw down a mass of the finest iron dust, and it will clump together into a mass. If A and R were equal, they would remain where they fell. If R exceeded A, they would move apart.

 

2. The shorter and straighter arrangement of lines of force between opposite poles seems, by intuition, to be an inherently stronger and more stable configuration.

 

3. Nature, again intuitively, appears to favour a stable order, or at least a tendency towards stability. In the case of magnetism, an imbalance between A and R would help to achieve this.

 

 

4. Statements asserting R greater than A seem to come preponderantly from the "over-unity" brigade, so I steer clear of that.

 

5. In the realms of quantum mechanics and the consideration of dipoles and monopoles, and even relativity, there seem to be hints as to an imbalance, but I can find no unequivocal statement.

 

Further help required!

[JustStuit]

Nature' date=' again intuitively, appears to favour a stable order, or at least a tendency towards stability. In the case of magnetism, an imbalance between A and R would help to achieve this.

[/quote']

What proof do you have of this? And how would this make attraction stronger? If it is stronger, there is a reason - not just that nature favors stability. This is not create force or weaken one.

[gcol]

I am not telling, I am asking. If I had proof I would not be asking. I presented a conjectural and hypothetical line of reasoning based upon vague and circumstantial evidence, as I thought I had made clear by my choice of words. Not clear enough for you, obviously.

[JustStuit]

I am not telling, I am asking. If I had proof I would not be asking. I presented a conjectural and hypothetical line of reasoning based upon vague and circumstantial[/b'] evidence, as I thought I had made clear by my choice of words. Not clear enough for you, obviously.

obviously

[JustStuit]

Having said' date=' post #10, that I would be surprised if Attraction (A) and repulsion ® were unequal, I am now not so sure. Because:

 

1. Throw down a mass of the finest iron dust, and it will clump together into a mass. If A and R were equal, they would remain where they fell. If R exceeded A, they would move apart.

 

2. The shorter and straighter arrangement of lines of force between opposite poles seems, by intuition, to be an inherently stronger and more stable configuration.

 

3. Nature, again intuitively, appears to favour a stable order, or at least a tendency towards stability. In the case of magnetism, an imbalance between A and R would help to achieve this.

 

 

4. Statements asserting R greater than A seem to come preponderantly from the "over-unity" brigade, so I steer clear of that.

 

5. In the realms of quantum mechanics and the consideration of dipoles and monopoles, and even relativity, there seem to be hints as to an imbalance, but I can find no unequivocal statement.

 

Further help required![/quote']

You stated that you believed this because, insinutating the following were true, or atleast you had knowledge to believe that they were true.

[Meir Achuz]

Why is the attractive force between identical magnets more then the repulsive force?

When you bring two bar magnets (of roughly equal strength) together with N facing S, the magnetic field of the second magnet is in the same direction as the magnetization vector (M) in the first magnet. Therefore it tends to increase that magnetization, increasing the attractive force between the magnets. If you bring them together with N facing N, the field in the second magnet opposes the magnetization vector in the first magnet and tends to weaken it. This makes the repulsive force less than the corresponding attractive force.