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Question about magnet

  1. Sep 7, 2007 #1
    Hi,

    I am new to this forum, and I just wanna say hi and I am glad that I am here. Now, I have one animation. Isn't the magnet always staying stationary, in one position? Thank you very much.

    Best regards.
     
  2. jcsd
  3. Sep 7, 2007 #2

    berkeman

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    What magnet? The animation would appear to show a fixed something in the middle (a magnetic pole?), and a moving object that is orbiting around the fixed object, under the influence of a central attractive force.

    That wouldn't work for magnets, BTW, because there are no magnetic "monopoles", only dipoles. So you can't have a North pole body and a South pole body that are isolated.

    Also, if those bodies were real (and attracted by something like gravity or electrostatic forces), the middle body would be moving some too -- the two bodies would orbit around their common center of mass.

    Welcome to the PF, BTW.
     
  4. Sep 7, 2007 #3
    Then how magnet dipole is create? There must be two poles. The electron its self is not dipole, so there must be some other charged particle like the proton. Please help. Thanks.
     
  5. Sep 7, 2007 #4

    berkeman

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    The basic magnetic dipole is an atom, with the "motion" of the "orbiting" electron(s) generating the magnetic dipole field. The "current" created by the "orbiting" electron is what generates the magnetic field. I'm using terms from classical physics when I say that.

    http://en.wikipedia.org/wiki/Magnets
     
  6. Sep 7, 2007 #5
    Isn't your animation a hydrogen atom/ or something 'trying' to correlate it to it?
     
  7. Sep 7, 2007 #6

    DaveC426913

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    Gold Member

    The animation is depicting an electron "orbiting" a proton. njama has assigned the two particles with N and S. He is imagining an atom as essentially a spinning magnet and wants to know why macro-scale magnets have stationary poles.
     
  8. Sep 8, 2007 #7
    Yes, that's my question. How is possible that magnet poles are not changing when the electron is moving all around the protons? To be dipole there must be 2 poles. Electron its self cant be dipole tiny magnet, because of the fact that there must be 2 opposite forces and also if the electron is dipole magnet its self, how then it will repel with another electrons, or again it is moving?

     
  9. Sep 8, 2007 #8

    HallsofIvy

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    The whole problem, then, is that your animation, an electron orbiting a proton, has nothing to do with magnets!

    It is even unrealistic in terms of charged particles (not magnets). An electron "orbiting" a proton would be accelerating and so radiating energy. Electrons do not "orbit" nuclei, they form "clouds" around them (even a single electron).
     
    Last edited by a moderator: Sep 8, 2007
  10. Sep 8, 2007 #9
    So please tell me then, where do the magnet dipoles come from?
     
  11. Sep 8, 2007 #10

    HallsofIvy

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    There is no magnetic dipole associated with a single hydrogen atom. There can be a magnet dipole associated with a hydrogen molecule depending upon the exact configuration.
     
  12. Sep 8, 2007 #11
    Can you give me some example, please?
     
  13. Sep 8, 2007 #12
    "It is composed of a single negatively-charged electron circling a single positively-charged nucleus of the hydrogen atom."


    "Even when there is no external magnetic field, in the inertial frame of the moving electron, the electromagnetic field of the nucleus has a magnetic component. The spin of the electron has an associated magnetic moment which interacts with this magnetic field. This effect is also explained by special relativity, and it leads to the so-called spin-orbit coupling, i.e., an interaction between the electron's orbital motion around the nucleus, and its spin. "

    http://en.wikipedia.org/wiki/Hydrogen_atom
     
  14. Sep 8, 2007 #13
    So, again the dipole magnet comes from the protons and electrons. Is it possible that the electron is standing in one place?
     
    Last edited: Sep 8, 2007
  15. Sep 8, 2007 #14

    DaveC426913

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    Perhaps it would be a useful demonstration to describe the structure of the simplest possible magnet. How many atoms are required, and what is their relationship to each other such that they form a magnetic material with a north and south pole?
     
  16. Sep 9, 2007 #15
    I think that one atom is tiny dipole magnet. I think that, in the atom or molecule there are 2 different charges (2 opposite forces), the protons and the electrons. So if one atom is one small magnet, then where do the opposite forces come from? Also see this.
     
  17. Sep 10, 2007 #16
    So, is it possible that the electrons are standing (not moving)?
     
  18. Sep 10, 2007 #17

    DaveC426913

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    No.

    No.


    A molecule can be a dipole. Water is a polar molecule. It has a definite shape (it is not spherical) and because of its molecular structure, the electrons tend to gather at one end (the oxygen atom tugs on them), leaving the other end (the hydrogens) positively charged. You now have a tiny magnet. When many molecules line up, you have a larger, more powerful magnet.
     
  19. Sep 10, 2007 #18
    Ok, thank you very much.
     
    Last edited: Sep 10, 2007
  20. Sep 10, 2007 #19
    And in iron, how are the atoms bonded? Are there also polar molecules?
     
  21. Sep 11, 2007 #20
    In the iron, there are no polar molecules.
     
  22. Sep 11, 2007 #21

    DaveC426913

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    Sorry, I must rescind my earlier claim that atoms do not make magnets.

    Some elements have atoms with electron shells that are not paired up. Iron is one. It's 3D shell should hold 10 electrons but it only holds 6 - 2 are paired but the other four are unpaired. These unpaired four are not distributed evenly around the nucleus - and the imbalance is what creates a magnetic moment. This is what makes iron attracted to a magnet.

    Further, the iron itself can become magnetized, meaning that a majority of the atoms align themselves so that their unbalanced shells line up an reinforce the overall magnetic field.


    http://www.coolmagnetman.com/maghow.htm
     
  23. Sep 11, 2007 #22
    To understand a magnetic dipole you have to understand the magnetic field that is created around a conductor which is carrying current: it deflects a magnet (compass needle, for example) at right angles to the direction of current flow.

    This site has an image illustrating this:

    http://www.walter-fendt.de/ph11e/mfwire.htm [Broken]

    The light blue vertical rod at the center is the current carrying conductor. The darker blue rings with arrows around it show the apparent circular configuration of the magnetic lines of force that come into being around the conductor when current flows. To the right you can see a red and green compass needle; red for north, green for south. It is pointing at right angles to the direction of current flow. If we were to place it on the other side of the conductor it would continue to be deflected at right angles to the current flow, but north would be the opposite direction than it is on the present side. The north and south poles seem to go in circles around the conductor.

    Now, if we make a loop of that current carrying conductor, those magnetic rings configure themselves like this:

    http://www.mne.psu.edu/me415/fall04/boeing2/magnetic%20field.jpg [Broken]

    and what we see is that on top of the loop (I say "on top" since it is oriented horizontally in the illustration) all the north-pointing arrows are now curving into the center of the loop. On the bottom they are pointing out and around. This is what makes the north and south poles of a magnet. Once you understand this you can see that a magnetic monopole is simply not possible, and also that there is no need for two different charges to make a dipole.

    Dave explained in a practical way why the electrons in certain atoms amount to current flowing in a loop and allow those elements to give rise to magnetic fields.
     
    Last edited by a moderator: May 3, 2017
  24. Sep 11, 2007 #23
    And how do moving charge produces magnetic field? How do then the electrons repel (because they have same charges). By your theory if 2 electrons acting like 2 tiny dipole magnets can attract them selfs?
     
    Last edited by a moderator: May 3, 2017
  25. Sep 11, 2007 #24
    I don't know.
    I don't know how they repell. I don't think anyone knows. It is, however, a well established property of electric fields that like charges repel.
    I'm not giving any personal theories here. The concept of a magnetic monopole is the "theory" here. I think it's a naive result of trying to break permanent magnets in two until you finally separate the north from the south pole. If you understand the relationship of magnetic fields to moving charges you see that such a thing isn't possible.

    Two conductors carrying current in the same direction are, indeed, attracted to each other. So are two loops of wire carrying current in the same direction. Apparently, electrons traveling in the same direction are no longer mutually repulsive, but attractive (edit: at right angles to the direction of travel). Don't ask me why or how, but it is a fact.
     
    Last edited: Sep 11, 2007
  26. Sep 16, 2007 #25
    By this picture http://www.mne.psu.edu/me415/fall04/boeing2/magnetic%20field.jpg [Broken] the magnet will always be in this http://img165.imageshack.us/img165/9905/untitledpg7.jpg [Broken]
     
    Last edited by a moderator: May 3, 2017
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