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Magnetic field or photon

  1. Aug 6, 2008 #1
    So, I have been reading various sources, and I am getting a little confused as to what electrons, protons, and neutrons generate when moving. Do they generate photons, or a magnetic field?

    I guess what I am trying to understand is, do any of the particles listed above have a magnetic field when at rest, or just when in motion? I understand that they will emit EM at a certain velocity. I guess a second question would be, at what speed is it required in order for one electron to emit one photon.
  2. jcsd
  3. Aug 6, 2008 #2


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    You're talking about the motion of charged particles right? The motion of charged particles would create a magnetic field circling (perpendicular) the movement of the charges. At rest there won't be any magnetic field. And this applies only to charged particles, neutrons don't count. There's also no emission of photons when this happens.
  4. Aug 7, 2008 #3
    I gotcha.

    Here is what is confusing. a permanent magnet, is that moving? How can I related a moving charged particle with a magnetic field to a permanent magnet, like lodestone, or rusted iron?

    what is causing the magnetic field? Wouldn't these particles have to be moving?

    If that is the case, when these particles start to move alot, due to heat, doesn't the curee effect suggest that they lose their magnetism?

    Sorry for all the questions, I am just confused. I don't understand how you can have a superconductor that is approaching 0K start to have an increase in its magnetic field, and if that same matter starts to approach 1000K, it loses its magnetic field due to the curee effect. You would think that if the molecules were vibrating because of the heat, that they would produce an even stronger magnetic field, wouldn't you?
  5. Aug 8, 2008 #4


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    You are mixing A LOT of things in one pot, especially things that aren't related to each other at all.

    1. Moving charges create magnetic field - this can be described via classical E&M.

    2. Any charge emits "photons", but these are virtual photons, per quantum electrodynamics.

    3. Accelerating charges created EM radiation - this can also be described via classical E&M. EM radiation is "light", so these ARE photons, real ones, not virtual.

    4. "curie temperature" deals with ferromagnetic material, not just simple, non-interacting charges or magnetic moment. When you heat a ferromagnet, you are adding a lot of energy to all the individual magnetic moment in side the material. They have enough energy to vibrate, spin around and tilt the magnetic moment direction, and frankly, do the hokey pokey. So the heat energy causes more disorder in the pristine arrangement of the magnetic moment. This causes the bulk material, the ferromagnet, to lose its bulk magnetism.

    It would help if, whenever you want an explanation of some sources that you read, that you actually cite clearly the sources. This will tell us if you've read it correctly, misinterpret what was written, or simply read the wrong info.

  6. Aug 8, 2008 #5


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    For a magnet, the magnetic field arises from atomic dipole moments as well as electron spin. Though not really an accurate picture, you can visualise an electron revolving around a nucleus as a current along a circular path. This gives rise to a small magnetisation. In ferromagnets, a lot of these dipoles are aligned in the same direction which gives rise to a net magnetisation, so in a sense the charged particles correspond to the electron "orbiting" around the nucleus.

    When the magnetised object is heated above it's Curie temperature, the resulting thermal excitation causes the magnetic dipoles to orient in different directions, effectively canceling out its net magnetisation.
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