Basic question about magnetic fields/permanent magnets

Discussion in 'Physics' started by norstudent, Feb 27, 2014.

  1. norstudent

    Thread Starter New Member

    Feb 26, 2014
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    Hi

    I'm reviewing magnetism on a very fundamental level, I have a brief question:

    My understand so far:
    - Magnetic fields, unlike electric fields are only produces by charged particles in motion

    - In non-magnetic materials, the electrons all produce individual magnetic fields, but due to their random orientations they sorta cancel eachother out

    - Where as in magnetized materials, such as permanent magnets, these fields are sorta aligned so that they DONT cancel eachother out

    My question:
    In magnetized materials/permanent magnets, do all these individual feels add up to eachother and strengthen?
     
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
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    sorta sorta


     
  3. norstudent

    Thread Starter New Member

    Feb 26, 2014
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    I realize my "sorta" statement was a bit vague, but I was actually quoting my instructional dvd, thus I wasn't sure myself either

    I guess what im asking:
    Does superposition apply when you have several magnetic fields in one area?
     
  4. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Yes they can either reinforce or cancel.

    Electrons carry an electric charge.

    Any moving electric charge generates a magnetic field, and the electrons are always in motion.

    The electric current in a copper wire is due to electrons in motion and this also generates a magnetic field due to this, however not all material objects carry electric current and yet respond to magnetic fields and some actually produce their own field.

    Except for ferromagnetic materials (Iron, nickel and a few other substances) no substance exhibits magnetic effects unless it is situated in an externally generated field.

    The response of materials to an external field is to align the material either parallel to the field (paramagnetic) or across (perpendicular to) the field (diamagnetic).

    Ferromagnetism is a strong form of paramagnetism.

    Ferromagnetic materials can form what are known as permanent magnets. That is they remain 'magnetised' when there is no external magnetic field. So they can generate a magnetic field in their own right. Copper is not a ferromagnetic material and cannot do this.

    The magnetic effect in copper wires is due to electrons that are 'free'. That is they are not part of any particular atom and move along the wire, whilst (obviously) the copper atoms stay in place.

    Electrons belonging to particular atoms are very important since not only do they determine the chemical properties of that atom, they also determine its magnetic properties.

    The electrons in an atom are circling round the nucleus of the atom in quite specific manner. Because they are travelling in orbit around the nucleus they generate a (small) magnetic field.

    In the atoms of many substances there are as many electrons going one way as there are going the other so the effects cancel out and there is no net magnetic field.

    However in iron atoms there are four electrons more going one way than there are going the other around the iron nucleus so these four electrons generate quite a powerful net magnetic field.

    Finally some atoms have one or two unbalanced electrons orbiting, but the atoms are arranged randomly so that the fields of one atom cancel the fields of nearby atoms with a net zero result.
     
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  5. norstudent

    Thread Starter New Member

    Feb 26, 2014
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    I see, that clears it up, thanks!
     
  6. amilton542

    Active Member

    Nov 13, 2010
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    Studiot, nicely done. Is this area of physics your main focal point of applied math?
     
  7. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Thanks, but remember this is a basic summary with several simplifications designed to keep the flow going.
     
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