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Old Oct 10th 2015, 06:57 AM   #1
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Magnetic Field in an Atom

How is magnetic field created in an atom according to quantum model? I mean, we are taught about the magnetic field by bohr's model which assumes that electron revolves around the nucleus in a circular path. But in reality it doesn't do so. So the field will keep changing its orientation. And it would be hard to align for them in external magnetic field if they are ferromagnetic or paramagnetic.
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Old Oct 10th 2015, 11:33 AM   #2
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I asked a similar question here:

Electron orbit

So to attempt to answer it seems some here believe the electric field of the atom varies over time and would thus produce a magnetic field (which I think follows from Maxwell's equations).

However, the "proper" answer will likely be related to the atom's spin which I suspect swamps out the more negligible effects of the electron "being unable to make up its mind" where it is. Welcome to the insane world of Quantum Mechanics!

I am kind of guessing at this. Will be interesting to see what the others have to say.
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Old Oct 10th 2015, 12:22 PM   #3
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Originally Posted by kiwiheretic View Post
I asked a similar question here:

Electron orbit

So to attempt to answer it seems some here believe the electric field of the atom varies over time and would thus produce a magnetic field (which I think follows from Maxwell's equations).

However, the "proper" answer will likely be related to the atom's spin which I suspect swamps out the more negligible effects of the electron "being unable to make up its mind" where it is. Welcome to the insane world of Quantum Mechanics!

I am kind of guessing at this. Will be interesting to see what the others have to say.
while reading your reply i was like "WHAT?" . please simplify a bit

I want to say that while electron is revolving around the nucleus, its path will keep changing and due to this, the magnetic field will also change, not only the magnitude but the direction too.

And about the maxwell equation, it is v = E/B, where v is velocity of electron and E is our holy electric field and B is Magnetic field. So, as v keeps changing for an electron then the ratio will also change. That's why we cant use this equation.

And i have heard about the electron spin but not the spic of the atom. But i assume both are same (Its just spin). And yeah it will affect the the electron.

Last edited by manshu; Oct 10th 2015 at 12:33 PM.
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Old Oct 10th 2015, 12:57 PM   #4
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I found a better explanation here in Eugene Khytoryanski video from about 12 minutes onwards. It skips some of the more complicated details, might be better.

Last edited by kiwiheretic; Oct 10th 2015 at 01:14 PM. Reason: More accurate timings of video
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Old Oct 10th 2015, 01:08 PM   #5
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Originally Posted by manshu View Post
And about the maxwell equation, it is v = E/B, where v is velocity of electron and E is our holy electric field and B is Magnetic field. So, as v keeps changing for an electron then the ratio will also change. That's why we cant use this equation.
The only way I know of getting a magnetic field is via a changing electric field. Although the electrons don't exactly orbit the magnetic field seems to be in keeping as if such motion did exist. Therefore, in my rather clumsy way of saying this, is that there is a rotating electric field giving rise to the magnetic field analogous to electric current flowing through a solenoid (coil).
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Old Oct 10th 2015, 11:01 PM   #6
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Originally Posted by kiwiheretic View Post
The only way I know of getting a magnetic field is via a changing electric field. Although the electrons don't exactly orbit the magnetic field seems to be in keeping as if such motion did exist. Therefore, in my rather clumsy way of saying this, is that there is a rotating electric field giving rise to the magnetic field analogous to electric current flowing through a solenoid (coil).
The other way of getting a magnetic field is by putting the material in external magnetic field and that external magnetic field may be caused by a magnet.

In solenoid, the plane of the rotating electron does not change. But in an atom the plane can change.
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Old Oct 12th 2015, 02:10 PM   #7
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musings of a failed chemist.

I spent some time in my youth trying to be a chemist (I failed)
In this field the complexities of the wave functions were simplified to produce what might be called iso-probability surfaces,
that is the locus of points around the atom at which the electron wave function gives the same probability.
These produce different shapes for different materials,
The four outer electrons of carbon, for example, produce a tetrahedral arrangement of lobes projecting out from the centre.

This indicates that the velocity pattern of the electron around the atom need not be spherical, thus the average sum of the fields from the electron need not completely cancel.
Indeed if we postulate a toroidal iso-probability surface, will this not be very similar to a solenoid and thus produce a magnetic field?

I admit I'm pushing a little knowledge a very long way way here...
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Old Oct 13th 2015, 12:09 AM   #8
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ahah...i dont get it...its hard to understand...please simplify
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Old Oct 16th 2015, 10:30 AM   #9
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What you indicate in your initial post is that because the electrons are whizzing about in all directions, on average, the magnetic fields they generate will cancel.
This is correct for many (most) materials.

My argument is that, in some materials the interactions between all the electrons in the atom (and the interactions with the electrons in neighbouring atoms) cause the probability of the electrons whizzing in some directions to be much higher than the probability of them whizzing in other directions.
This means that, for certain materials, the average of the magnetic fields of (some of) the electrons does not completely cancel.

However as I stated in my previous post, I am rather extrapolating and guessing a bit based on limited knowledge.
Perhaps someone else out there will reveal I am totally wrong...
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Old Oct 16th 2015, 11:14 PM   #10
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Originally Posted by MBW View Post
What you indicate in your initial post is that because the electrons are whizzing about in all directions, on average, the magnetic fields they generate will cancel.
This is correct for many (most) materials.

My argument is that, in some materials the interactions between all the electrons in the atom (and the interactions with the electrons in neighbouring atoms) cause the probability of the electrons whizzing in some directions to be much higher than the probability of them whizzing in other directions.
This means that, for certain materials, the average of the magnetic fields of (some of) the electrons does not completely cancel.

However as I stated in my previous post, I am rather extrapolating and guessing a bit based on limited knowledge.
Perhaps someone else out there will reveal I am totally wrong...
let us assume u r right, there is some magnetic field in an atom (say A). Then what will be happening in the atom right next to it (say B)? Well, according to lenz's law, the magnetic field in atom B should be opposite to that of atom A. And i think it contradicts the fact of domain in ferromagnetic material, doesn't it?

Edit : I forgot to laugh..: ahhahhaah
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