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Why do dipoles attract/repel?

  1. Jun 11, 2013 #1
    What is the key reason?
    I mean if you think about it, poles are just something we create to distinct the magnetic field.
    But they don't exist. Why do magnets attract/repel?
    Is it because of the dipoles?

    They want to aline themselves?

    Btw, are the dipoles in ceramic magnets equally the same dipoles in Neodymium and equally the same with the flow of current in a solenoid?
     
  2. jcsd
  3. Jun 11, 2013 #2
    There are several different kinds of dipole: electric dipole, magnetic dipole, and mesons are a dipole for the color charge. One basic way to think of a dipole is that it is basically a positive charge held a little distance away (by a rigid rod, perhaps) from a negative charge. Thus one side likes attracting to negative charges, while the other side likes going to positive charges.

    Two dipoles can attract or repel based on their orientations. If the plus charge of one is right next to the positive of the other, they will repel. But if you turned one of them 180 degrees, they would attract, since now the positive of one dipole is very close to the negative of the other. In this way, they do tend to align with one another.

    Things are a little more complicated for a magnet since in reality there is no magnetic charge--every "positive" pole comes paired with a "negative" pole. But it still is legitimate most of the time to think of the dipole in that way. To see how the analogy holds, you have to study how electric charge in motion creates a magnetic field--just like the solenoid you mention.

    But on an atomic level, for most magnetic materials, the reason for the magnetic dipole moment of the material is that each of the the individual atoms/molecules is working like a little solenoid (the electrons are circling around thus creating a magnetic field).
     
  4. Jun 12, 2013 #3
    But what is the simplest definition to a magnetic moment?
    What determines the strength of the magnet? We can't really say that a magnet can apply a force of such, because in reality it takes two dipoles to attract/repel and apply a force.
    But from a dipole, can we predict the force, or assume how much force is possibile or something?
     
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