Magnetism question

[lukeperry91]

After asking my physics teacher, chemistry teacher, and my tutor, I still don't have a clear understanding of the cause of magnetism due to a lack of explanation. I understand that the positive/negative sides (dipoles) of atoms in a magnet align, but I don't understand how they don't cancel each other out. I'll try and do a bit of a diagram:



-+  -+  -+  -+  -+  -+  -+
                             North pole
-+  -+  -+  -+  -+  -+  -+  

I don't understand how the adjacent delta negative and positive terminals of each atom or molecule do not cancel, and that the only source of attractive forces isn't from each final atom/molecule's positive terminal depicted by the final '+' signs at the righ side of the rather shoddy diagram. So, I don't understand how magnetic forces can increase/decrease without increasing/decreasing surface area.

Now I know that they CAN in fact vary in strength, but I don't know how. One explanation that arose as a possibility in my mind was if all magnets were metallic lattices, and the electrons all migrated to the south pole/negative terminus, therefore creating a large net positivity at the north pole/positive terminus.

After reading through the www.wikipedia.org article on magnetism, more specifically the 'sources of magnetism' area, I got the feeling that that might answer my question, but it's far too advanced for me. I was wondering if anyone more knowledgeable than me could perhaps dumb it down, the link to the article is: http://en.wikipedia.org/wiki/Magnetism#Sources_of_magnetism

Most of what I've said probably sounds dumb because physics isn't my strong point,  so I apologise in advance for any silly mistakes

Thanks!
Luke

[TrueTears]

There are 2 main basic types of magnetism.

1. The flow of current (negative charges) which creates magnetic field.

Say you got a rod and it falls through a magnetic field all the electrons will be pushed to one side and hence one side of the rod is negative and the other side is positive. This creates an EMF which creates a current hence a magnetic field is formed.

2. Electromagnets.

In an unmagnetized object, all the magnetic domains are pointing in different directions. But, when the metal became magnetized, which is what happens when it is rubbed with (or placed near) a strong magnet, all like magnetic poles lined up and pointed in the same direction. The metal became a magnet.

[lukeperry91]

There are 2 main basic types of magnetism.

1. The flow of current (negative charges) which creates magnetic field.

Say you got a rod and it falls through a magnetic field all the electrons will be pushed to one side and hence one side of the rod is negative and the other side is positive. This creates an EMF which creates a current hence a magnetic field is formed.

2. Electromagnets.

In an unmagnetized object, all the magnetic domains are pointing in different directions. But, when the metal became magnetized, which is what happens when it is rubbed with (or placed near) a strong magnet, all like magnetic poles lined up and pointed in the same direction. The metal became a magnet.

Thanks TrueTears, but my question is more what makes a magnet able to produce a force, Heinemann says that its just aligned dipoles, but I'm asking why they don't cancel.

wiki: "    * Electric currents, or more generally moving electric charges, create magnetic fields (see Maxwell's Equations).
    * Many particles have nonzero "intrinsic" (or "spin") magnetic moments. (Just as each particle, by its nature, has a certain mass and charge, each has a certain magnetic moment, possibly zero.)
"

I sort of understand the first dot point, but the second eludes me.

[/0]

My teacher said that magnetic fields have to do with the quantum spin number of electrons, which is related to the angular momentum of the electrons. Electrons can be spin up or spin down, and apparently if the spins all align in the same direction then you have a magnetic field.
*I am not sure about this, some of the uni guys might have a better understanding*

I'm not sure where your diagram comes from, but to me that looks like an electric field, which is a different thing from a magnetic field. Electric fields are created by charged dipoles aligning in a certain direction.

What I'm sure about is that the theory of magnetism relies on the domains of a magnet aligning. I don't think this refers to the 'electric dipoles' though.

[TrueTears]

Teacher also said that even we are not even sure how they are formed?

[lukeperry91]

Yea, my tutor colin said it was uni physics

[mark_alec]

My teacher said that magnetic fields have to do with the quantum spin number of electrons, which is related to the angular momentum of the electrons. Electrons can be spin up or spin down, and apparently if the spins all align in the same direction then you have a magnetic field.
*I am not sure about this, some of the uni guys might have a better understanding*

That is indeed the reason. Electrons have a spin (just a name, nothing is actually spinning classically), that has an associated magnetic moment.

[QuantumJG]

After asking my physics teacher, chemistry teacher, and my tutor, I still don't have a clear understanding of the cause of magnetism due to a lack of explanation. I understand that the positive/negative sides (dipoles) of atoms in a magnet align, but I don't understand how they don't cancel each other out. I'll try and do a bit of a diagram:



-+  -+  -+  -+  -+  -+  -+
                             North pole
-+  -+  -+  -+  -+  -+  -+ 

I don't understand how the adjacent delta negative and positive terminals of each atom or molecule do not cancel, and that the only source of attractive forces isn't from each final atom/molecule's positive terminal depicted by the final '+' signs at the righ side of the rather shoddy diagram. So, I don't understand how magnetic forces can increase/decrease without increasing/decreasing surface area.

Now I know that they CAN in fact vary in strength, but I don't know how. One explanation that arose as a possibility in my mind was if all magnets were metallic lattices, and the electrons all migrated to the south pole/negative terminus, therefore creating a large net positivity at the north pole/positive terminus.

After reading through the www.wikipedia.org article on magnetism, more specifically the 'sources of magnetism' area, I got the feeling that that might answer my question, but it's far too advanced for me. I was wondering if anyone more knowledgeable than me could perhaps dumb it down, the link to the article is: http://en.wikipedia.org/wiki/Magnetism#Sources_of_magnetism

Most of what I've said probably sounds dumb because physics isn't my strong point,  so I apologise in advance for any silly mistakes

Thanks!
Luke

Ok I think I understand what you are asking:

1.)

I still don't have a clear understanding of the cause of magnetism due to a lack of explanation. I understand that the positive/negative sides (dipoles) of atoms in a magnet align, but I don't understand how they don't cancel each other out.

You can induce a magnetic field from varying electric fields and vice-versa (i.e. this is how 'electromagnetic waves' work). So basically you can use that to explain why if you run a current through a wire a magnetic field is created. Permanent magnets are formed by if you use a magnetic substance (i.e. Iron) and you actually run a magnetic field through this metal what you do is change this whole random array of iron magnet atoms (which oppose eachother, hence, no magnet) to these atoms being arranged all aligned with eachother (which actually gets them to work with eachother), therefore giving you a magnet. This answers why they don't cancel eachother out because they are aligned with eachother. A cool experiment is to attach a magnet to a transformer and turn it on. The transformer's alternating current actually jumbles all the magnetic fields of the atoms up causing it to no longer be a magnet.

So, I don't understand how magnetic forces can increase/decrease without increasing/decreasing surface area.

This doesn't make sense! Are you referring to the magnetic field strength or the force it puts on charges.

The magnetic field strength is a property of the magnet! You can make a super magnet by adding a metal to the molten mixture, hence that would make it stronger.

[lukeperry91]

   

So, I don't understand how magnetic forces can increase/decrease without increasing/decreasing surface area.

This doesn't make sense! Are you referring to the magnetic field strength or the force it puts on charges.

The magnetic field strength is a property of the magnet! You can make a super magnet by adding a metal to the molten mixture, hence that would make it stronger.

It means that if they cancel (which they don't) then the only uncancelled positive dipole will be on the edge, lol.. dw

Thanks for your explanation, I look forward to learning more about this at uni!