1 magnet, 2 polarities

[5614]

firstly the title is not the 'whole picutre' !

 

as a slight side-track from the Motor Physics thread, i wondered how a single magnet could have varying polarities.

 

like i understand the phsyics of a normal bar magnet, but in this case we have a bar magnet (in a circular shape) which goes 'north, south, north, south' 4 times, resulting in 8N + 8S so a total of 16N+S (where N = north and S = south!).

 

so if you look in this image:

 

you can see the magnet i am referring to running around the outside of the metal 'disc'.

if you take a normal bar magnet labelled N and S and take one end, e.g. N and run it around the outter circular magnet it is attracted/repelled... so this single magnet obviously has varying polarities across is, rather than at each end, how is this possible?

 

it is ONE magnet with one split at one point where it is glued together, it was possibly one bar magnet that was bent into a circle.

[swansont]

It's a multipole magnet. I think all you have to do is put on a localized strong field, well above saturation. Then you move a little, and do it in the opposite direction.

[5614]

so what effect does this have on the electrons... or does that sound stupid?

 

i dont really know much about magnets on an atomic scale, i know the magnetic field is caused by the angular momentum of the electrons, but i dont know how polarities work.

 

how does polarity work?

 

how does it work with this multi-pole magnet? surely as a metal where the electrons are 'free' to move they could move around and an electric current could effect it?

[swansont]

It's not the conduction electrons that are affected, AFAIK. It's the electrons that stay with the atom. Since they have a fixed angular momentum with respect to the atom, and the atom is in a lattice structure, you end up with a net magnetic moment for a macroscopic part of the material, called a domain. The domain's field can point in different directions (but not randomly); you get a stronger magnetic field if you get more domains to align and thus fewer that anti-align.

[5614]

ok, so what's the difference between the e- in the north pole of the magnet compared to the e- in the south pole of the magnet?

 

[edit] e- = electron (just in case!)

[Kedas]

Just to give you a few examples of many little magnets on one piece of metal:

Your old cassette tapes, the harddisk that is sitting in your PC tells you how many magnets are on it.

1bit = 1magnet