Quote:
Originally Posted by adman
Alex - most of these arguments go way over my head - but this one doesn't seem to make sense - can you expand on this for me...?
Adam
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What he's trying to say, erroneously, is that it that the movement of the electrons about the nucleus of the atom is creating an electric current which forms the field.
Problem is, the atoms in most materials are actually electrically neutral, as the balance of charge between the electron cloud around the atoms and the nucleus is about equal. The electrons of an atom usually come in pairs whose spin is up and down (can't have two of the same spin in the same orbital...(Pauli Exclusion Principle)). If the orbitals are filled with up/down pairs, the dipole moment of the atoms is effectively zero. An atom will only show a magnetic moment if the orbitals are partially filled...i.e. some of the orbitals have only one of the electrons in a pair, either up or down. What happens with ferromagnetic materials is that the electrons in the atoms become predominately up or down in those partially filled shells...and that, along with the charge carried by the electron creates the field. They usually align themselves to the prevailing magnetic field they find themselves in, or are forced into that alignment via physical processes. They form what are called magnetic domains within the material...small magnets, if you will.
An electric current implies a flow of electrons. Try measuring the current in a ferromagnetic material. You won't find one.