# The inconsistent quantum physics and magnetic theory

1. May 18, 2012

### hds123523000

This question bothers me a long time and finally I decided to ask here.

The classic theory fails to deal with electron orbiting around atomic nucleus because energy has been emitted if we assume electron continuously orbits which leads to the collapse of the electron-nucleus model. But in real life the model is really stable. So, physicist proposed that electrons dont orbit continuously, instead, appear with possibility (quantum theory), which seems solved this problem perfectly.

However, in magnetic theory, the origin of the magnetic field of atoms is from the current of electrons. I am wondering if it is consistent with the quantum theory mentioned above, which is the possibility of electrons and doesnt generate current. It is quite difficult for me to think that electrons appear in possibility (at not completely random position) and generate current at the same time.

Is any expert can explain it to me? Many thanks in advance.

2. May 18, 2012

### ZapperZ

Staff Emeritus
There are still quantities such as "orbital angular momentum", spin, etc... that generates magnetic fields (in fact, that's how these are defined), but if you look at what they are, these are not in the same classical sense.

The problem here is that ALL our measurements are classical. So we have this thing called a magnetic field, we know that some atoms have magnetic moment, but the quantum description that produces such field does NOT look like charges moving around in circles. So at some point, we have to accept, at least for now, that magnetic fields is the measurable outcome of such a description.

Zz.

3. May 18, 2012

### EWH

Perhaps this just gives more interesting questions rather than an answer, but the zitterbewegung interpretation of electron movement at least is more readily visualizable than the usual non-explanations.

4. May 18, 2012

### hds123523000

ZapperZ, I think you spotted out more interesting points. Yes, we cant explain orbital angular momentum in a quantum concept.

So, this is something you think unsolvable, at least now. Does everyone agree? Or I missed something? Thanks for suggestion.

5. May 18, 2012

### ZapperZ

Staff Emeritus
I gave the standard answer based on what you can find in QM texts. I assumed that this is what being asked for here. There are many other formulation and interpretation of QM that will offer varying explanations.

Zz.

6. May 18, 2012

### Meir Achuz

1. The magnetic field of a iron atom is due to the aligned intrinsic spins of the valence electrons, and not their orbital motion.

2. There are also orbital magnetic moments given by mu=-e L/2mc, even though the electron is not moving in a classical orbit.

7. May 18, 2012

### hds123523000

Hi, Meir Achuz

Can you explain your point 2 more deeply. For example, why it has such magnetic momentum but doest obey the classic orbit? Where this magnetic moment originally from?

8. May 18, 2012

### samalkhaiat

We get these numbers by solving Schrodinger equation which does not describe any orbital motiom for the electrons. However, in the smiclassical limit, Schrodinger equation provides us with "picture" consists of something that look like "orbital motion" plus quantum correction. For this reason we still use the term "orbital angular momentum" to describe that part of ANGULAR MOMENTUM which (mathematically) looks like the classical angular momentum.

Sam

9. May 19, 2012

### Meir Achuz

If you calculate the energy shift in a uniform magnetic field B, the answer is
$$\Delta E=-e{\bf L\cdot B}/2mc}$$. No mention is said about the electron's classical orbit. Thinking classically about a quantum system is like trying to understand a fluorescent light in terms of a kerosene lamp.

10. May 20, 2012

### hds123523000

Hi, Sam

Your reply is interesting and a little beyond my understanding. You think the megnetic can be generated without electron orbiting? I think everything is out of a physical reason. But what is the physical reason of that magic equation.

You mentioned the semiclassical limit. I am wondering what is that?

11. May 20, 2012

### hds123523000

Meriz
In your opinion, if I abandon the classic theory. Where is magnetic moment from physically in quantum theory? The possibility can generate magnetic moment? It is difficult to convince me in that way.

Best

12. May 20, 2012

### Maui

The assertion"God does not play dice!" was found to be wrong many years ago. Time to move on(or find a more comprehensible reality :tongue:).