/sci/ - Science & Math

[Anonymous No.10790330]

So electrons have spin "up" or "down" and thats it. If i put a bunch of electrons in a box and apply a uniform constant direction magnetic fiels through it, do the electrons orient themselves to the field? How many are up and down then?

[Anonymous No.10790359]

They won't have any orientation unless you measure them.

[Anonymous No.10790451]

>>10790330
i think the closest real world example to this situation would be a crt gun , something like this (?):

https://www.youtube.com/watch?v=9zpP-OPqX4c

but the electrons apparently do not change their spin (I think), they just fallow the magnetic path via their electric charge, so i guess we could say that in this case the electric charge/magnetic field becomes the prevalent interaction and the spin of every electron becomes insignificant (?).

I gues the only way you can force an electron to change spin via magnetic field is only under specific conditions like only on magnetic solids ( magnetic metals)

btw this old videos are great!

[Anonymous No.10790468]

>>10790330
>So electrons have spin "up" or "down" and thats it.
Due to quantum fuckery, a superposition of both.
>If i put a bunch of electrons in a box and apply a uniform constant direction magnetic fiels through it, do the electrons orient themselves to the field?
Yes, although ambient temperature causes them to spread a bit. Stronger magnetic fields cause stronger alignments.
>How many are up and down then?
Roughly half, although it slightly favors those that follow, rather than oppose the field (something something boltzmann statistics)

[Anonymous No.10790524]

>>10790468
but wouldn't this mean half of then will not behave like an electron with a charge that follows a well stablished behaviour under a magnetic field?. for example in a crt gun you would not be able to focus the electron bean if you had "roughly half" of then not respond to the magnetic field of the focus coil (in some cases this is a electrostatic type that uses metal plates or rings)

[Anonymous No.10790795]

>>10790524
Spin is not an really an electromagnetic property, and certainly not a classical one.

[Anonymous No.10790800]

>>10790795
so this question is not valid in the first place?
what is the fundamental property of an atom that would make it magnetic (or able to create a magnetic field)? .

[Anonymous No.10790838]

>>10790800
In physics and in science, we reuse words that probable shouldn't be reused.

Spin is about Momentum but it doesn't mean anything is moving in the sense of a displacement of space because the measurement of that changes what you see. It is more of an accounting of the energy.

Think of it like a math thing. If you "spin" a top, the vector of Torque comes out the top, but unlike a velocity vector, nothing is moving in that direction... This is weird because mathematically you are overlaying the math space onto a physical space and it is easy to equivocate the two.
Physicists work in the math space and are very careful as to what manifests into the physical space and what does not.
It's not much different than saying "demons do it!" except that it works...

As for the fundamental property of an atom that makes it magnetic, in QM it has to do with its Diamagnetism, and the permittivity of free space

[Anonymous No.10790879]

>>10790524
>"roughly half" of then not respond to the magnetic field
They do respond, it's just that half of them respond in the oppisite direction.
>in a crt gun
There are two sources of magnetism: particle spin, and movement of an electric charge. You're talking about the former, while a crt/electron gun involves the latter.

Firing an electron over several inches/feet is a much higher magnitude force than the quantum splitting you're concerned about, and it's linear as opposed to angular.