Fan for life...

[Tim]

I refer to magnets in terms of isotropic and anisotropic with isotropic  meaning they have a randomly orientated crystalline structure which has the ability to hold charge in different orientations(often referred to as 'un-orientated') while anisotropic magnets have fixed orientation as they're introduced to a magnetic field during the cooling stage of construction. To the best of my knowledge isotropic magnets are not just weakened anisotropic magnets and its very much to do with how the crystalline structure of the magnets is aligned by the introduction of a magnetic field. Its fair to say anisotropic magnets  are stronger and produce a brighter tone from the pickup while isotropic magnets produce a warmer tone although both share the sweeter voice so associated with Alnico magnets.
The majority of Alnico V magnets are anisotropic construction from '64 onwards. The Alnico II and IV we use are isotropic while the Alnico V we use is mainly anisotropic although we do use isotropic Alnico V for certain applications, often aging the magnets too.

[MDV]

I sit corrected.

It still isnt a correct application of the term though ;)

[Dmoney]

f**king magnets, how do they work?

[MDV]

Magic.

Or

If you want the 'classical' faraday/maxwell answer they're produced by alternating the direction of an electric field (inc. in a material)

Thats not really an explanation though. It doesnt give a mechanism.

If you want the quantum mechanical (well, the quantum electrodynamics to give the field, no pun, its proper name) explanation then its that certain atoms have a net spin (spin being a quantum property/quantum number that all charged particles have), because theres a leftover from all the spins of the particles its composed of. All charged particles have a positive and a negative varitation of the spin the particle is capable of carrying and all available energy levels are occupied once for each available spin (see fermi principle for an explantion). If you have a leftover spin then you can find the magnetic field moment

m = g.Q.s/2.m

Where q ia the charge, m is the mass and g isnt normal g, its 'g factor' which I've forgotten everything about except that its dimensionless and s is the spin (1/2 or 1, positive or negative, zero is a possible spin but gives no magnetic moment).

If this happens then photons (virtual photons, that you cant  see, they just exist nebulously as a feild) move through the atom in the direction of the net spin and in proportion to the m, magnetic moment.

Which means that magnets are all made of molecules which are themselves magnets. A magnet is also therefore definitionally anisotropic. Any magnetic molecules are non-isotropic (they have an asymmetry because of their spin whereby they make a magnetic field in a particular direction) and a 'magnet', i.e. any lump of stuff that has a magnetic field has a magnetic field because some proportion of the magnetic atoms or molecules in it (assuming that it contains non magnetic atoms and molecules, which it will) are facing the same way.

If all of them are facing in random directions then all directions are equally magnetic and their is no net field. This would be isotropic.

Sorry for the maths. Really, I am.

And for any of the more scientifically literate members (I know youre there!) for any errors - its been a while since I did QM. Please correct if you spot anything.

[MDV]

Oh, oriented and un-oriented/orientated are much better terms.

I was thinking that 'fixed' and 'unfixed' would be better, while hoping for a world where people in technical, engineering and scientific professions (which includes me) dont feel that they are payed by the syalable so as to avoid hyper-corrections like calling a magnet 'isotropic' cos it sounds, like, way more cleverer (which also occasionally includes me, but at least I sometimes try not to!)

[Dmoney]

well i was thinking it was all down to Jesus.

but that makes sense to me, I wasn't really looking for answer, but in relation to the ICP tune, i've read people posting "opposite poles attract" which is a description of what they do, rather than how the do it.
I like how the song miracles goes on to accuse scientists of being liars.
say what you want about ICP, but i think they have some good marketing ideas and i find the whole subculture they head fascinating... in a way.

the only quantum anything i know is that in Boolean algebra things have a on/off true/false 1/0 state, but in quantum physics statements can in theory be both on and off, etc. maybe im mistaken, or i had some discussion about quantum computing that i probably didn't understand. It's not really my field! where as coded orthogonal frequency division multiplexing on the other hand...

[MDV]

Yeah, its called superposition of states.

Schrodingers cat is a thought experiment designed to illustrate its weirdness (and was actually intended to show that it surely must be wrong because its so weird).

All particles have a bunch of discrete properties (i.e. they have integer or fractional value and a particle can only have one value, not anywhere in between one value and the next) like spin. The spin of an electron can be 1/2 or -1/2, for example. But, if that electron is made in an event that created a pair of electrons from something that has no spin, like a photon (that can happen by the way: high energy photons can and do spontaneously degenerate into an electron/anti-electron pair) then the spin of one has to be 1/2 and the other has to be -1/2 because spin is conserved, so the total spin before and after the event must be the same.

But

Until you find out what each electrons spin is they both have both spins at the same time. Its only when its observed that the particle 'chooses' a state. Until then it has all possible states at the same time.

This is the same principle that is the basis for quantum computers - they're supposed to be ultrapowerfull because rather than have a transistor be on or off and give a 1 OR a 0, spin (in the case of the quantum computers as well, there are lots of quantum numbers, I dunno why I'm harping on about spin) can be up AND down, giving a 1 AND a 0, so computational power increases exponentially with the number of computational units

And now I'll stop spouting physics at you :lol:

[Roobubba]

Yeah, its called superposition of states.

Schrodingers cat is a thought experiment designed to illustrate its weirdness (and was actually intended to show that it surely must be wrong because its so weird).

All particles have a bunch of discrete properties (i.e. they have integer or fractional value and a particle can only have one value, not anywhere in between one value and the next) like spin. The spin of an electron can be 1/2 or -1/2, for example. But, if that electron is made in an event that created a pair of electrons from something that has no spin, like a photon (that can happen by the way: high energy photons can and do spontaneously degenerate into an electron/anti-electron pair) then the spin of one has to be 1/2 and the other has to be -1/2 because spin is conserved, so the total spin before and after the event must be the same.

But

Until you find out what each electrons spin is they both have both spins at the same time. Its only when its observed that the particle 'chooses' a state. Until then it has all possible states at the same time.

This is the same principle that is the basis for quantum computers - they're supposed to be ultrapowerfull because rather than have a transistor be on or off and give a 1 OR a 0, spin (in the case of the quantum computers as well, there are lots of quantum numbers, I dunno why I'm harping on about spin) can be up AND down, giving a 1 AND a 0, so computational power increases exponentially with the number of computational units

And now I'll stop spouting physics at you :lol:

Tsk, typical physicist, ignoring the chemical mechanism behind magnetism - that being the unpaired electron states of certain materials!

:P

[MDV]

Tsk, typical chemist, thinking that an unbound electron state isnt implicit in a non-zero spin summation in any atomic or molecular configuration!

;)

[FELINEGUITARS]

Whooosh!

The sound of this thread going over my head

It's amusing (and possibly educational if you have time to look up what is being discussed) but it's starting to sound like two scientists arguing as to whose slide rule is bigger than the others

[nfe]

Martin Luther has a lot to answer for. You guys and your protestant science.

[Roobubba]

Tsk, typical chemist, thinking that an unbound electron state isnt implicit in a non-zero spin summation in any atomic or molecular configuration!

;)

I was more having a dig at your profligate use of the non-specific term 'particle', but I'm not a chemist any more anywa, so Ner :D

[MDV]

Tsk, typical chemist, thinking that an unbound electron state isnt implicit in a non-zero spin summation in any atomic or molecular configuration!

;)

I was more having a dig at your profligate use of the non-specific term 'particle', but I'm not a chemist any more anywa, so Ner :D

The rules do generally apply to 'particles', though, but, which includes molecules and their properties, see.

I didnt, I confess, include descriptions of superpostion of waves and probability distribution functions, in which case, its a guitar forum, get a grip! :lol:

But, entirely out of interest (which hopefully you share), my personal favourite related phenomenon is youngs slits with a single photon and that you can build an interference pattern firing one photon through the diffraction slits at a time, meaning a single photon must have passed through both slits at the same time, and so been in two places at once (i.e. it travelled as a wave), unless you put a detector on one silt in which case, because you looked for it, you find a photon in one place, not the other, and the 'wave' becomes a probability distribution function which is collapsed to a single location by observation and you lose the interference pattern. Dont look = wave. look = particle. Try to reconcile the two and you have to conclude that a particle either doesnt exist in transit - its emmited as one, it arrived at the last detector as one, but getting there its not one, or it can be in two places at the same time unless you look for it. Makes my brain hurt, I like it.

[Roobubba]

Tsk, typical chemist, thinking that an unbound electron state isnt implicit in a non-zero spin summation in any atomic or molecular configuration!

;)

I was more having a dig at your profligate use of the non-specific term 'particle', but I'm not a chemist any more anywa, so Ner :D

The rules do generally apply to 'particles', though, but, which includes molecules and their properties, see.

I didnt, I confess, include descriptions of superpostion of waves and probability distribution functions, in which case, its a guitar forum, get a grip! :lol:

But, entirely out of interest (which hopefully you share), my personal favourite related phenomenon is youngs slits with a single photon and that you can build an interference pattern firing one photon through the diffraction slits at a time, meaning a single photon must have passed through both slits at the same time, and so been in two places at once (i.e. it travelled as a wave), unless you put a detector on one silt in which case, because you looked for it, you find a photon in one place, not the other, and the 'wave' becomes a probability distribution function which is collapsed to a single location by observation and you lose the interference pattern. Dont look = wave. look = particle. Try to reconcile the two and you have to conclude that a particle either doesnt exist in transit - its emmited as one, it arrived at the last detector as one, but getting there its not one, or it can be in two places at the same time unless you look for it. Makes my brain hurt, I like it.

Yes, that's a cracking experiment! And almost very relevant to me, as (I suspect you remember), I'm an X-ray crystallographer: diffraction is my bag. Although in my case, it's diffraction of X-rays from a protein crystal and then working back to guestimate the phase of each diffraction spot (which we call 'reflections'... sigh) to subsequently reconstruct the electron density within the crystal (and hence to build a model of the 3D structure of the protein). Still, Bragg's law (that constructive interference only occurs when 2dsin(theta)=n(lambda)) comes quite directly from the very elegant double slit experiment you mentioned.

I hated quantum mechanics at Uni - in fact I ended up not revising it for finals so I could focus on other topics (as I had been rather ill and fell behind during my undergraduate time). I was very very very lucky that the QM question on our physical chemistry finals paper was excruciatingly hard, so everyone who attempted it did really badly! I had a big gamble to answer just the required number of questions and it paid off wonderfully :D I must say, as much as quantum mechanics now interests me, I find I'm much more adept at enzyme kinetics - a tedious subject by most accounts - but one which can tell you intricate details about, for example, reaction mechanisms and their inhibition, which are otherwise nigh on impossible to determine.

Now then, where were we?

[Twinfan]