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Can anyone tell me the properties of monopoles?

  1. Dec 20, 2006 #1
    can anyone tell me the properties of monopoles?
     
  2. jcsd
  3. Dec 20, 2006 #2
    I didnt know monopoles existed, have they made one yet? I guess you're talking about a magnet with only one pole right?
     
  4. Dec 20, 2006 #3

    FredGarvin

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    He could be refering to acoustic monopoles. It's tough to say though since the OP is very vague in what he is looking for.
     
  5. Dec 21, 2006 #4
  6. Dec 21, 2006 #5
    I suggest you to read a paper written by P.A.M. Dirac, i think during the forties.
    For sure youn know Maxwell equations. you can check their asymmetric form between the electric and the Magnetic field right? let's say just divE=rho, divB=0 right?

    Dirac postulated divB=i rhom!!!! a pure immaginary density of magnetic charge.
    And the same for the vector J(electric)----> iJm(magnetic).

    After this assumptions you can check by your own that you can write the maxwell equations in a really nice form representing the electric and the magnetic field with a point on a complex plane. W=E+iB. now you can check that the equations are invariant under a "duality" trasformation, a rotation on th complex plane made under U(1)=SO(2). This is the aim of the theory put more symmetry on it. Unfortunately we've never see a magnetic monopole even if we cut lots of time a magnet :-).
    Doing this the Multipoles Series of the two fileds become very similar also... see the article.... Physical review volume 74 number 7 first october '48 "The theory of Magnetic monopoles" you'll see that it implies the elctricity quantization===> eg=1/2 n (hbar)c !!!! e elactron charge g fundamental magnetic charge n an integer and the rest you know for sure....

    bye
    marco
     
  7. Dec 21, 2006 #6
    yes, magnetic monopoles, I was wondering if superconductors might be a type of monopole because of its magnetic properties
     
  8. Dec 21, 2006 #7

    ZapperZ

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    No, they are not. A superconductor exhibits a perfect diamagnet property. That certainly isn't a "monopole".

    Zz.
     
  9. Dec 21, 2006 #8
    No magnetic field can penetrate a superconductor, this fact is manipulated by SQUID magnetometers which as far as I am aware are the most sensitive magnetometers we have, capable of sensing variations in field intensity of the order of a few femto Teslas.
     
  10. Dec 21, 2006 #9
    Raymond,

    Adding to what ZapperZ has said, let me tell you that magnetic monopoles (as described by Dirac) are a theoretical concept of which there is not yet any experimental evidence (although their existence is highly anticipated). Such monopoles were construced to make the quantum EM theory fully symmetric : ie complete duality between electrical and magnetic fenomena, so for each electric charge there is a corresponding dual magnetic charge. Look at the website that i provided in the link. Such monopoles are used in QCD as well to describe quarkconfinement in terms of perturbation theory after transforming the big (ie very strong interaction) electrical coupling constant to a low magnetic coupling constant (so that pertubartion theory can be applied).

    marlon
     
  11. Dec 21, 2006 #10

    disregardthat

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    If you cut a normal magnet with + in one end and - in the other in half, would you get a monopole?
     
  12. Dec 21, 2006 #11

    ZapperZ

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    If you could, we would never have Maxwell equations in its current form.

    Zz.
     
  13. Dec 21, 2006 #12

    disregardthat

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    What makes the magnet a magnet, and not just a normal object. what powers can this magnet object contain to affect other obejcts far away from it?
     
  14. Dec 21, 2006 #13
    Like a starfish, if you break a magnet you get two smaller magnets. And like.. a water molecule with its electric dipole moment, it will affect (attract and reorient) other nearby objects but you wouldn't ascribe "powers" to it. And.. like an electromagnet-coil, a magnet is magnetic because it contains domains of spinning electrons.
     
  15. Dec 21, 2006 #14
    Didn't you play with magnets in primary school? Basically, like poles repel and unlike poles attract, negative sticks to positive. Also, a charged particle will follow the magnetic field lines.

    The magnetic field arises in the first place because of moving charges, basically a charged object will become a magnetic object if it is moving. Sometimes this effect occurs at a sub-atomic scale, small charged particles called electrons whizzing about in an ordered manner cause a magnetic field.
     
  16. Dec 23, 2006 #15
    Huh ? Lorentz force anybody ?

    Sorry, i don't get this ? Are you saying that an electric point particle moving in a magnetic field, becomes a magnetic point particle ?

    When ?

    marlon
     
  17. Dec 23, 2006 #16
    I think what bill's saying is true, but loose. Charged particles do tend to spiral around strong field lines, and indeed (classically) magnetic fields result from charged particles being viewed in a frame that isn't comoving. A "spinning" electron could perhaps even be described as a magnetic point particle, but it is still a dipole rather than a monopole.
     
  18. Dec 24, 2006 #17
    No, it cannot. This is exactly what i was objecting against. The concept of magnetic point particle does not exist in both classical physics and special relativity.


    regards
    marlon
     
  19. Dec 24, 2006 #18
    Badly phrased I'll admit, but I wasn't talking small scale here.



    How about ferromagnetism.
     
  20. Dec 24, 2006 #19
    Ok, but still i don't get the point

    Ohh ok, got it now.

    But the "spinning electrons" (they are NOT actually spinning, remember that) are certainly NOT magnetic monopoles. Besides, such magnetic properties arise due to a collective behaviour of many magnetic dipoles (ie the spins you talk about) all interacting together with each other is some way. It is the "way of interacting" which determines whether a material is ferro/anti ferro or ferri magnetic.

    marlon
     
  21. Dec 27, 2006 #20
    Sorry billiards, but Marlon is right.

    Do you know Lorentz force?
    The total force (F) acting on a charged particle (q) passing trough a magnetic field with velocity v is: F=q(VxB). Where "x" it's the vector product, so the particle will move perpendicular to the magnetic filed. WON'T follow the magnetic lines.

    For Jarle.
    I think that billiards was trying to tell you this:
    In nature we observe that a little closed wire wich has moving electrons in it is equivalent to a magnetic dipole. This is Ampere theorem statement.
    At an elementary level we can approximate atoms with Bohr interpretation (Planetary). So electrons in their orbits seems like charged wires (Amperian currents). putting differents object in a solenoid we can check that they react in different way to the applied magnetic field. Basically we have:diamagnetic, paramagnetic and ferromagnetic materials. It works like the compass there is a magnetic torque that alligne the magn dipole with the lines. This is just a model that rapresent objects with an Avogadro's number of little tiny magnetic dipoles. If you buy a matter physics book you can learn a lot more. You can check also the relativistic interpretation of electromagnetism wich explain by itself ampere theorem, and you can find a lot more (SPIN-orbit interaction...). I suggest YOU "Physics of atoms and molecules" Bransden and Joachain.
    bye
    Marco
     
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