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What is magnetism

  1. Dec 23, 2008 #1
    What is magnetism?...preferably no links to other sites...just a conceptual answer...
     
  2. jcsd
  3. Dec 23, 2008 #2
    Re: Magnetism

    Electromagnetism is one of the four elemental forces.
    Each electron act as a magnet alone, but in most materials electron's spins are random oriented, but in a magnet most of the spins are equal.

    Why that happens? Someone may say because electron charge and whatsoever, but it is as elemental as we can get. Its like asking what was before the Big-Bang.
     
  4. Dec 23, 2008 #3
    Re: Magnetism

    It is part of the electromagnetic force. Strictly speaking, magnetism is the relativistic part of the electric force. This is why you see the velocity in the formula for the magnetic force (and why the force is zero if the particle is at rest with respect to a second magnetic field). The "electric force" and the "magnetic force" are tied together...but you can set up situations where the effect of one or the other seems to predominate. If you want a good mostly non-mathematical explanation of this see R.Feynman's "Lectures on Physics Vol.II - Chapter 1."
     
  5. Dec 23, 2008 #4
    Re: Magnetism

    yup...I guess my question was a bit closer to that...

    Thanks, your answer is clear...I'll look into his lectures...
    Could the same be said about the electric force in respect to the magnetic force?
     
  6. Dec 23, 2008 #5

    jambaugh

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    Re: Magnetism

    Your question is pretty broad. Do you have refrigerator magnets? Have you ever played with them? Then you know "what magnetism is" in terms of the phenomenon. What more do you want? I could tell you it is little invisible pixies which fly around ferromagnetic metals or current carrying wires and push on them with their wings. But that wouldn't be helpful. It would also be no less helpful than another "explanation" in terms of string theory or virtual photon interactions.

    It is a phenomenon, or as has been said one component of the general electromagnetic phenomenon. If you want to "know what it is" beyond watching a bar magnet pick up iron filings then you'll need to study electromagnetism with all the math to get a more precise description.

    If you want to "know what it is" in terms of some deeper phenomena then you open up the whole chicken and egg infinite regress. At some point you must stop and just study how it behaves.

    However here's what it is.... Magnetism is a component of electromagnetism (which component depending of the observer's inertial frame) which in turn can be described as the force due to a U(1) gauge symmetry of the vacuum. If you add a small circular degree of freedom to any particle in addition to its three spatial translational degrees of freedom and its three rotational degrees of freedom then you must ask how does the particle's orientation in this hidden symmetry change when you move it from point A to point B and or let time pass. The answer is there is some connection between event points which we call the electromagnetic potential. What is this extra degree of freedom? Call it phase, call it another dimension, you can't see it so it's "only a model". It's a darn useful model for describing all the consequences of electromagnetism succinctly but in the end you only can be positive about the observed phenomena.

    The other physical forces can similarly be modeled in terms of hidden "gauge" degrees of freedom for particles and these (apart from gravity) together form a model called The Standard Model. Gravity works the same way but the degrees of freedom are not hidden, they are the usual degrees of freedom involved in rotating and translating a particle around.
     
  7. Dec 23, 2008 #6
    Re: Magnetism

    I lost you there...
     
    Last edited: Dec 23, 2008
  8. Dec 23, 2008 #7
    Re: Magnetism

    If you mean can you set up experiments where each "appears" as a separate force that yes. In fact, this is how you study them in elementary physics so you can look there for the setups. But the electric force and magnetic force are two different aspects of the same thing as the movement of an electric charge generates a magnetic field. If you understand differential equations see Maxwell's equations...it is a set of 4 equations that describe how electricity can cause magnetism and vice versa (and I must say, they are perhaps the most beautiful equations in all of classical physics as they compress all of the knowledge about electricity and magnetism into a few short statements).
     
  9. Dec 23, 2008 #8

    jambaugh

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    Re: Magnetism

    Yes. I beg your pardon. I was being a bit obtuse on purpose. I don't however know where to begin as I don't know where your level of understanding starts.
     
  10. Dec 24, 2008 #9
    Re: Magnetism

    At least you gave me an insight of where we are.

    Electricity and Magnetism are 2 aspects of the same phenomenon...so doesn't that imply that we could fuse electricity and magnetism and getting something else...sort of like what was once a more original force that now exists in stability as electromagnetism.
     
  11. Dec 24, 2008 #10

    jambaugh

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    Re: Magnetism

    Not by "fusing electricity and magnetism" per se. They already are "fused" aka unified.

    What we mean by "electricity and magnetism being 2 aspects of the same phenomenon" has to do with unifying space and time in special relativity. If you have a bar magnet which is generating a magnetic field then if I'm moving past you I don't see pure magnetism I see a combination of magnetic and electric fields. Similarly if you have a statically charged ball I'll see a moving charge i.e. a current and thus a magnetic field along with the electric.

    Now there are attempts to unify electro-magnetism with other forces. Electro-weak unification works quite well although there are some peculiarities begging explanation.

    Attempts at unifying these with the strong force usually lead to mechanisms by which protons can decay and several experiments have failed to observe this even at very very low levels of probability. Research has stalled a bit and I suspect a major change of paradigm will be needed to move beyond what we have now which is the Standard Model.
     
  12. Dec 24, 2008 #11
    Re: Magnetism

    I see, thanks...and one further question: it should be possible to separate electricity and magnetism much how electricity and the weak force are separate, right?
     
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