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How does a magnet work?

  1. Apr 13, 2004 #1
    newbie here - i know this question is tangled up with the question, "what is a field?" and "how does a field work?", but to keep it simple (ha!) can someone please try to explain how a magnet works? ie, how is force transmitted from the magnet to its surroundings? does a magnet "do work"? sorry if this sounds like a troll, but it is such a fundamental question and i, for one, cannot answer it...

    btw, i am not interested in a textbook definition of "field", as that does not explain how it operates. i am also not too interested in a discussion of the "exchange of virtual particles" since no one seems to be able to explain what virtual particles are or how they operate either. thanks.
  2. jcsd
  3. Apr 14, 2004 #2


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    A filed is an equation that tells us the vqlue of a quanitity such as force, which acts at a particular position at that field. In other words it describes how strong a force is on a particle at a particular point. A magent creates a magnetic field by having the magnetic moments of its electrons aligned in the same direction. this causes other ferromagnetic materials to try and align their magnetic moments to oppose the effect pof the magnet and give and overall force of zero at every pint in the magnetic field.
    Last edited: Apr 14, 2004
  4. Apr 15, 2004 #3


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    Well, many fundamental questions are often the most difficult to answer to.Without carriers of EM force (ie.virtual photon exchange mechanism) It would be very difficult to find explanation...
  5. Apr 16, 2004 #4
    To attempt to explain classically.


    Charges in motion produce the electromagnetic field, the field is an object that permeates all of space and tells all the other particles with charge what force to feel in relation to the other charges.


    Atoms have electrons orbiting them, these electrons are moving charges and so produce an electromagnetic field. This in effect means there is a magnetic force towards any other magnetic material.

    That is a very basic explanation, but is the best compromise in terms of understanding and simplification.
  6. Apr 16, 2004 #5


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    I guess the orginal poster has already seen/read classical explanation offered above (when he stated he was not interested in textbook definition of field and it's classical relation to the source of field;and he also rejects formalism of quantum interpretation how interaction occurs).The question is actually very profound ,but the poster is perhaps not aware of that.
  7. Apr 17, 2004 #6
    Well no, the question is pretty dumb if that is the case.

    Classical electromagnetism explains perfectly well how a magnet works. If you reject the real quantum interpretation of how it works then it is impossible to explain how they work. They work because of quantum effects.
  8. Apr 17, 2004 #7


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    Classical EM can't explain concept of field but in math terms.Neither QFT hasn't settled this issue yet as concerns my opinion .Just math approach and treating the interactions is different.FYI,nobody knows for sure what QM field in a physical reality is (if you know,well..).His question isn't dumb as concerns this part.

    P.S. There's no dumb qustions,just dumb answers.
  9. Apr 17, 2004 #8
    Great questions!!
    So, I have "one" myself on this topic. Is the magnetic field generated only by electrons? Or, can other negatively charged particles also generate a magnetic field? How about positive charges, can they generate a magnetic field?
  10. Apr 18, 2004 #9
    Something I don't understand: magnetic fields can cause acceleration of magnetic materials, in terms of energy, are the magnets doing work on the magnetic materials, if so where is the energy coming from?

  11. Apr 18, 2004 #10
    Really good question!! lets see if some of the mentors can offer us up 'current thought' (or a bettter explaination)

    (posting gets me subscribed to the thread, and I would love to see where this one goes!)
  12. Apr 19, 2004 #11
    thanks to all for the replies. first, let me state that i do not reject the QM interpretation, i am just saying that it merely provides a mathematical statement of the probability of results from a given interaction, but does not explain what is actually going on (which surely must be the most intriguing question, yes?). hence, my comment that no one seems to be able to explain what virtual photons are or how they operate (if i am wrong about this, and someone CAN actually explain how virtual photons operate, i would love to hear about it).

    so, let me get this straight -
    we do not know how a magnet works, correct?
    we also do not know how ANY field operates, correct?
    which means that we do not know how photons operate, or even what a photon is, correct?

    thus, we also do not know what gravity is, nor an electromagnetic field, nor what the strong force is, correct?

    however, we do have amazing accurate descriptions and equations that can predict the results of interactions between subatomic particles (QED) that hold true all the way to ultra-macro situations, correct?

    thanks again.
  13. Apr 19, 2004 #12
    jnorman said: "so, let me get this straight -
    we do not know how a magnet works, correct?
    we also do not know how ANY field operates, correct?
    which means that we do not know how photons operate, or even what a photon is, correct?
    thus, we also do not know what gravity is, nor an electromagnetic field, nor what the strong force is, correct?"

    Well, you don't really have it straight.

    The only things we DON'T know about classical electromagnetic fields is why the field of a point charge is radial (although that seems reasonable), why its strength is what it is, why the strength decreases with the square of the distance from the charge (although that doesn't seem unreasonable), and why the fields of multiple charges add the way they do. At least I think that's all we don't know.

    But given just those few things, we DO know how magnets work, we DO know how fields operate (at least we know what they do), we DO know what an electromagnetic field is.

    I'll let others tell you what we know about the other things, but we know more or less the same sorts of things about them too.
  14. Apr 20, 2004 #13
    jdavel - okay, so how does a magnet work? how does a field communicate with the particles which lie within its influence?
  15. Apr 20, 2004 #14
    Your assertion that we do know how EM fields work is properly rebutted by your own words "we DO know how fields operate (at least we know what they do)." Just as you suggest, we haven't the slightest clue how EM fields work. If we did, we wouldn't require a virtual photon to describe such interactions. We have, as you suggested, deduced accurate descriptions of their behavior in relation to their state, but we still have no idea why they behave in such a way.

    jnorman - You would probably find a great deal of interesting material in the Theory Development forum! I have followed several threads from Steve McQueen and Antonio Lao discussing exactly what you seek in a more in-depth fashion. Here are some examples:
    New Field Theory
    Wave-Particle Duality

    The honest answer is that we don't know what you ask.
    Last edited: Apr 20, 2004
  16. Apr 20, 2004 #15

    I think the difference between what we're each saying is wrapped up in our sloppy uses of words like "what", "how", "why" etc.

    For thousands of years, people tried to understand the physical world by asking "why" questions. And they got exactly nowhere! Even by the end of the 16th century most people still believed the earth was at the center of the solar system. Their "reasoning"? Why would God put it anywhere else?

    So physicists decided to give up starting with "why" questions. The postulates of physics are answers to "what" questions. For example: What is the speed of light in a vacuum?, What is the force on a unit charge at a distance r from a charge q? What is the acceleration of a mass m when a force F is applied to it? What's the difference between the laws of What do the characteristics of

    Once we have a few postulates, physics answers "why" questions with one or more of the postulates. For example,

    Q: Why do magnets attract?
    A: Because the force on a unit charge at a distance r from a charge q is q/r^2 and the laws physics are the same in all inertial frames.

    Q: Why are the oscillations of a pendulum simple harmonic motion?
    A: Because F=ma

    Not everyone thinks those questions (let alone the answers) are very interesting, but physicists do. Partly because they know that's the best we can do.
  17. Apr 21, 2004 #16
    is it at all possible that by discussing these things that we may actually learn something beyond the what? and maybe even the why?

    for example. from my understanding space or vacuum has attributes such as permitivity, permeability, conductivity and whats the other one? ( excuse the spelling)

    Could a magnetic field simply be created by the distortions of these attributes of local space or vacuum by the attributes of the mass involved?

    What is the current thinking on the nature of space/vacuum?
  18. Apr 21, 2004 #17
    magnetism can be shown with wires... You can do the operational defintion of Ampere's law with your handy right hand rule... You see that 2 wires running parallel to each other (rather close) attracts on another... and oppose directional currents repel... Then you can show magnetism thru the eddy currents and how cutting slots in them reduces it and show how the vending machine works with magnetism... etc etc... So its important stuff...

    Magnetism "dies" when the material "dies" or is gone, destroyed, or natural decay...

    A popular phrase in classical physics books is "the existance of a monopol has not yet been verified" So if so... hehe. Laws all change again! w00h00
  19. Apr 21, 2004 #18

    Agreed. I sometimes wonder about the the monopole theory. Magnetism, as we seem to know it, is not an emmissive phenomenon in the sense of particles or photons shooting-off from a source never to return.
    Indeed, everday evidence seems to suggests that the magnetic expression is a localized "loop force phenomenon" requiring N/S "poles" to exhibit the event.
    To my knowledge, monopoles have never been observed in nature and never experimentally produced.
    Yet this still begs the question: What, exactly, comprises the externally reaching field we know of as "magnetism" Something MUST be happening in that field that is wholly different in it's absense. Of this, we can be sure.
    Damn! A most common phenomenon little understood.
  20. Apr 21, 2004 #19
    It should be remembered that the magnetic field of a "source" is "attached" to the source. If a ferrous type object is placed within the field such that it is attracted to and accelerates towards the magnetic "source" the event is not without conservation.
    That is, the magnet "feels" the attraction and acceleration and physically reacts in an effort to move towards the ferrous object, even if the magnet is restrained. Think of a stretched rubber band.
  21. Apr 22, 2004 #20
    Indeed this is an interesting observation. The "what" does tend to be the first step in understanding a phenomenon, and indeed "why" seems to be trivial anymore with regard to science. However, it seems that after having answered the "what" science tends still not to be satisfied. We also want to know "how." How is the magnetic force transmitted? "A field" is not a sufficient answer to satisfy curious minds, fields are a mathematical representation of something detected but unseen. In order to fully utilize magnetic fields in the most effective way in our technology, science must understand how magnetic fields operate in order to be certain that our current "what" definition is accurate 100% of the time. Perhaps we know all there is to know in regards to magnetism's behavior, and understanding the "how" won't bring any striking revelations. On the other hand, perhaps monopoles do exist in some far reach of the universe. Perhaps gravity itself is magnetism! We'll never know these things for sure until we discover the method by which magnetism operates.
    Last edited: Apr 22, 2004
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