Magnetic Polarization (Magnetization) versus Electrical Polarization (Polarization)

Discussion in 'General Electronics Chat' started by idontknoweverythingyet, Aug 7, 2013.

  1. idontknoweverythingyet

    Thread Starter New Member

    Aug 7, 2013
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    When a permanent magnet (or an electromagnet) comes across a magnetizable material (for now ignore diamagnetic materials and anti-ferromagnetic materials -- paramagnetic, ferromagnetic, and ferrimagnetic materials are abundantly used), it coerces the magnetizable material's magnetic dipoles to align with the externally applied magnetic field. In electrostatics, by contrast, an externally applied electric field will make the electric dipoles in a dielectric align against the externally applied electric field. In the extreme case of an ideal conductor, the plus (+) and minus (-) charges separate so as to completely screen out the externally applied electric field.

    So why is it that magnetic flux lines cause magnet dipoles to align with the externally applied magnetic field while electric flux lines cause electric dipoles to align against the externally applied magnetic field?
     
  2. LDC3

    Active Member

    Apr 27, 2013
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    In one word, semantics.
    If you examine closely, you will see that the opposite poles (or charges) are attracted together. With magnetism, both ends are in the same item so the field is curved. With electric field, the ends can be separated and the field is as short as possible.
     
  3. idontknoweverythingyet

    Thread Starter New Member

    Aug 7, 2013
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    I understand that the nature of electric field lines in electrostatics and magnetic field lines in magnetostatics are very different basically owing to the observation of two different and separable electric charges versus the observation of two different, yet seemingly inseparable magnetic charges.

    However, there is a convention that the magnetic dipole is considered to follow the right-hand rule. That is, if the bound current of a positive charge is oriented counterclockwise around a circular orbit, the magnetic field lines are said to "begin" in the direction parallel to the circular orbit's surface normal.

    That's a lot of words, so consider a picture for clarification.
    http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/imgmag/magfi.gif

    See the hand? The thumb points in the direction of the surface normal while the arrows indicate the direction the positive charge is moving (in the counterclockwise direction).

    While typing this, I realized that electrons that are responsible for magnetic dipoles in matter are negatively charged and therefore the convention will be reversed for them. This would mean that the application of an externally applied magnetic field will cause the magnetic dipoles to orient exactly opposite to the externally applied magnetic field.

    But this contradicts what I've read in books about magnetic dipoles. I think I'm more confused now.
     
  4. LDC3

    Active Member

    Apr 27, 2013
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    And I'm too tired to try to understand tonight. I'll try tomorrow.
     
  5. idontknoweverythingyet

    Thread Starter New Member

    Aug 7, 2013
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    I forgot I had asked this question. Any further thoughts to add to the question LDC3?
     
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