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Electron Energy

  1. May 26, 2006 #1
    Hi Everyone,

    I was reading this post here (https://www.physicsforums.com/showthread.php?t=206&page=3&highlight=oscillator) where the poster was asking what keeps electrons from falling into the nucleus of the atom due to the unlike charges of the electron and neutron. This raised another question in my mind. I know that ferrous materials like iron have magnetic domains in them which at the atomic level look like small magnets that have their own fields. From what I understand, they say that it is the spin and movement of the electrons in the atoms that produce this “permanent” magnetic field naturally in the material. (This is of course speaking of an unmagnetized chunk of iron). I know from my limited knowledge of quantum mechanics that electrons are expressed in terms of wave functions; they are not particles like the classical model suggests. If a “moving” electron creates a magnetic field in the atom, does it not have to expend energy to do so? This does not make sense considering some of the explanations people gave concerning base energy levels and orbitals. If I have an atom with an electron at the lowest energy level creating a magnetic field from its “movement” then where is the energy to create the field coming from? Perhaps the word move is what is confusing me but I know from basic physics that in order to have movement, work has to be done by something, so what is the ‘something’ that is doing the work to keep the electron moving (looking at is as a wave of course not a particle).
     
  2. jcsd
  3. May 26, 2006 #2
    No. "Work" is the transference of "Energy". If the magnetic field causes no work to occur there's no energy expended. Think of light, where a moving electric field generates a moving magnetic field etc. Light doesn't consume energy and fade away with distance.

    I don't know about work done when a permanent magnet accelerates a nail. Perhaps it's on google somewhere or somebody else can say.
     
  4. May 26, 2006 #3
    Strictly speaking, the electron has infinite energy. What you measure (with a degree of inaccuracy) is the "dressed energy" of the electron. Similarly all other obeservable properties of the electron like mass and charge are dressed due to its interaction with vacuum (sea of virtual photons).This is one of the fundamental problems in Quantum Electrodynamics, i.e the "self energy" of the electron, or the interaction of the electron with its own field.

    I will have to defer answering your question regarding spin and magnetic moment as I'm heading out ATM. Sorry for the brief answer :)
     
  5. May 26, 2006 #4
    "The law of conservation of energy is obeyed, but momentum is not conserved" is something I have a particular interest in.
     
  6. May 26, 2006 #5
    Thanks for the information... now I'm confused though. How can an electron have infinite energy? This reminds me of a seemingly simple question I asked my physics professor concerning the charge of an electron. I gave him the following scenario. If there are two electrons near each other, how does one know that the other one is near and how they repel each other? Regardless of how the electrons got next to each other what causes them to repel away?? His reply was that the electrons continually emit virtual photons all the time which hit the other electron and repel it away… As nice as this sounds, that doesn’t exactly answer the question… what are virtual photons and how can they be constantly emitting from the electron all the time?? They have to come from somewhere and there has to be some sort of energy source for the electrons ‘infinite’ supply of energy… if not then I am forced to assume that the electron is either creating energy all the time (which I know can’t be right) or it is some kind of perpetual motion machine (which I also know can’t be right). I must be missing something here. What annoys me more about this is that the few explanations I have read don’t seem to directly combat the question but merely talk around it using math. I know that the quantum world is difficult to directly observe but are there any accepted theories out there that can actually explain what is physically happening, rather than diverging into a bunch of fuzzy math to get around it? It seems that some scientists tend to be extremely good at using complex mathematics to explain the interactions of these phenomena but yet tend to hide behind the math rather than attempting to directly explain why the interactions take place. Sorry for my ranting, just my observations :tongue:
     
  7. May 26, 2006 #6
    Hmmm this also makes me wonder. If no energy is expended from the electron when there is no work done on the magnetic field, then what happens to the electron if it's magnetic field does do work on something? Particularly if the electron whose field is doing work happens to be located at the lowest energy level of its atom? Since the electron can't go below the certain energy level where is the energy coming from for its field to do work on anything? :confused:
     
  8. May 26, 2006 #7

    Gokul43201

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    If you had a free proton at rest in some inertial frame, there will be an electric field due to its charge. Are you okay with that ?

    Now this proton clearly has no energy (ignoring self energies and such). But if you put an electron near it, this new electron will be attracted towards it. Clearly, work is done on the electron. Are you okay with that ?

    Magnetism can be approached in the same manner. Instead of a charge, you have a magnetic moment (either spin or orbital). This moment is sitting around happily, and in its rest frame produces a magnetic field. Now if you take another moment (or a bunch of them, like in a magnet) and put it nearby, it will feel a torque that rotates it. In just the same way as above, work is done on this moment to rotate it.

    If you didn't have a problem with the first scenario, you shouldn't have one with this either.
     
    Last edited: May 26, 2006
  9. May 26, 2006 #8
    I couldn't find anything on Google explaining where the energy comes from when a magnet performs work attracting a nail.
     
  10. May 26, 2006 #9
    Ok I definitely understand and agree with you; when you set up those circumstances, those events will happen. My question is how does that happen and why? What does the work on the electron to move it towards the proton? I know that it is the difference in charge but what is physically taking place, what is expending energy to cause the interaction? I understand that the subatomic particles have an intrinsic charge but where does this charge come from and how does that factor when one describes work being done? Sorry for all the questions but this has really been bothering me for a while.
     
  11. May 27, 2006 #10
    isn't the electron cranking out "virtual particals" from the vacume and that is where the energy is coming from that prevents the electron from falling into the nucleus?
     
  12. May 27, 2006 #11
    It's a bit like gravity, jdo. What does the work on a brick when you drop it? In this respect you can think of Gravity as exhibiting negative energy. There's "potential" energy at one point and less at another, closer, point. Charge is akin to gravity, but is different. Have a search on Google and you should be able to find something that gives you a concept for your electron and proton beyond. I don't think you'll find an explanation for charge though, because it's one of those very fundamental things. Charge is charge.
     
    Last edited: May 27, 2006
  13. May 28, 2006 #12
    Hi Farsight,

    As far as the field interactions go, I don't disagree with anything you have said, but it is the "source charge" problem that has been bothering me. We just have to assume that the electron has this unidentified energy always present to create it's charge and give it the momentum to create a magnetic field, which for all practical purposes is limitless since the electrons never loose energy below their base energy level (please correct me if I am making incorrect assumptions here). It makes me wonder how an electron's magnetic field can do work on anything without affecting the electron itself (assuming that it is already at the lowest energy level). It just seems to me that we are making some assumptions about things that we don't know about... I could run off into a pointless rant but that wouldn't help me understand what is happening here. However, could anyone here give me any reference material to any new theories out there that may adequately explain what's up with the charge of the electron and where it comes from? I know that physicists like Dr. Myron Evans from the Alpha institute of Advanced study (www.aias.us) has a good theory that seems to be gaining interest from the scientific community. But the explanations he gives are all pretty much fuzzy math and way over my head. Would anyone have any other suggestions?
     
  14. May 28, 2006 #13

    Gokul43201

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    The work is done by the field, but this doesn't mean anyone is losing "energy". All that's happening is that energy is being converted from potential to kinetic. There's no "loss" in the process.

    To raise another example, does the earth expend energy when a meteor is pulled towards it ? No. But they gain some kinetic energy to make up for the loss of potential energy between them.
     
  15. May 28, 2006 #14

    Gokul43201

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    Your concepts are all mixed up. I suggest you put aside worrying about this question until you've learned the concepts formally.
     
  16. May 28, 2006 #15
    Okay, thanks for the clarification.
     
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