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Magnetism help for an amatuer

  1. Nov 4, 2005 #1
    So these earth's magnetism is supposedly produced inside these generator-like chambers inside of which various chemicals are mixing to form some sort of giant electromagnet, in theory, right?

    But whether this is or isn't true, where does magnetism come from at its root? Do photons have magnetism?
     
  2. jcsd
  3. Nov 4, 2005 #2

    Mk

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    I think it is unknown to the cause of the Earth's magnetic field. Is it the Peltier-Seebeck effect? http://en.wikipedia.org/Peltier-Seebeck_effect

    Where does magnetism arise from? Electrons.

    There are different types of magnetism, lucky for you, the three main being: Diamagnetism, Paramagnets, and Ferromagnetism. We'll go backwards.

    Ferromagnetism is the kind you normally observe. Refrigerator magnets, speaker magnets, wallet magnets, permanent magnets.

    Ferromagnetism is due to the direct influence of two quantum effects: quantum spin, and the Pauli exclusion principle.
    The spin of an electron, (something you can't visualize correctly) combined with its orbital angular momentum, results in a magnetic dipole moment and creates a magnetic field. (if you need to, you can imagine the electrons spinning around). The dipoles tend to align spontaneously, without any applied field.

    Ferromagnetism manifests itself in the fact that a small externally imposed magnetic field, say from a solenoid, can cause the magnetic domains to line up with each other and the material is said to be magnetized. The driving magnetic field will then be increased by a large factor which is usually expressed as a relative permeability for the material. Ferromagnets will stay magnetized after having been aligned to this exterior magnetic field. Called hysteresis. The fraction of the saturation magnetization which is retained when the driving field is removed is called the remanence of the material.

    All ferromagnets have a maximum temperature where the ferromagnetic property disappears as a result of thermal agitation -- the Curie temperature. You know that heat is actually just the atoms shaking around, after the atoms shake around enough they aren't all aligned the same way!

    So really, all the electrons are "spinning" the same way, and that creates the field.
    http://hyperphysics.phy-astr.gsu.edu...sol/domain.gif

    Diamagnetism is a very weak form of magnetism, that needs another magnetic field to work. It is the result of changes in the orbital motion of electrons. Diamagnetism is repelling. Diamagnetism is found in all materials; however, because it is so weak it can only be observed in materials that do not exhibit other forms of magnetism. Some diamagnetic materials that should be recognized are water, pyrolitic graphite, and superconductors.
    http://www.exploratorium.edu/snacks/diamagnetism_www/

    Paramagnetism is closely related to diamagnetism, and also needs an external magnetic field. It occurs temporarily, when its magnetic dipoles align with the external field. Some paramagnetic materials that should be known are oxygen, aluminum, and sodium.

    Photons are not magnetic.
     
  4. Nov 4, 2005 #3
    Thanks for answering! One last question.

    Does a positron have magnetic properties?
     
  5. Nov 4, 2005 #4

    Mk

    User Avatar

    Yes, positrons have an electric charge of +1. Do you understand that "electricity and magnetism are two sides of the same coin?"
     
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