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What makes a magnet, a magnet?

  1. Sep 5, 2009 #1

    Fuz

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    What makes a magnet, a magnet? Ok... I know about polarity and all that. I just dont get why certain elements and compounds aren't magnetic. For example, why isnt an apple magnetic? Thats a little extreme but I think you get the point :smile:
     
  2. jcsd
  3. Sep 5, 2009 #2
    In the apple, the contributions to the total magnetic field due to all the atoms are oriented in random directions, and on the average they cancel each other out. In a magnet the magnetic fields produced by individuals atoms are aligned so that they add up.
     
  4. Sep 5, 2009 #3

    Fuz

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    Ah, so technically everything is a (very weak) magnet, right? Well why would a normal magnet orient its atoms opposed to the apple?
     
  5. Oct 2, 2009 #4
    Not everything is a weak magnet, in fact, an apple is actually diamagnetic because it contains mostly water. I don't know too much about the physical properties of ferromagnetic materials so I can't answer your question.
     
  6. Oct 2, 2009 #5
    Not all atoms produce magnetic fields, only ones with unpaired electrons do. Actually, in a material, the most energetic electrons (usually called valence electrons) don't 'belong' to particular atoms, they actually move about the about the material quite a bit. They have kinetic energy from this, and the kinetic energy for a magnetic system is higher than for a non-magnetic system. From quantum mechanics, there is something called the exchange energy which is lowered if electrons have their spins lined up, so the exchange energy favors magnetism. Whether a material is magnetic or not comes from the competition of these two terms in the energy; if making a material magnetic causes the kinetic energy to be increased less than exchange energy is lowered, then the material will be magnetic.
     
  7. Nov 14, 2009 #6
    What makes a magnet a magnet is that Iron, Cobalt, and Nickel are attracted by it. Anything that attracts those 3 elements, pure or as alloys is considered a magnet. But your question realy is how do magnets work. My best answer is that nobody knows.

    Beware of complicated explainations which in the end only explain the observable effects. As for the electron spin explaination consider this. All other elements with 2 outer orbital electrons are not magnetic. How does a local affect of two electrons spinning in the same direction create attraction or repultion at a distance. We just don't know yet.
     
  8. Nov 15, 2009 #7

    Vanadium 50

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    Not all alloys of iron, nickel or colbalt (or gadolinium or dysoprosium, the two other ferromagnetic elements) are ferromagnetic. Many stainless steels are not, and even the Cu-Ni alloy in nickels is not.

    Second, there are whole books written about magnetic order in general and ferromagnetism in particular. In normal ferromagnets, it's quite well understood (there are more exotic ferromagnets that are an active area of research). Each atom acts as a tiny magnet, and the quantum mechanical exchange interaction causes them to spontaneously line up.
     
  9. Nov 16, 2009 #8
    An object that is surrounded by a magnetic field and that has the property, either natural or induced, of attracting iron or steel.
    An electromagnet.
    A person, a place, an object, or a situation that exerts attraction.


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    Last edited by a moderator: Nov 16, 2009
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