Question

Okay last physics question:
3. Explain briefly how moving electric charges at an atomic level produce magnetically polarized domains in a sample of iron, and how the domain structure differs for a magnetized iron bar and one that is not magnetized.

Answer 1

Ok, This gets back to my other point on saturation. The domains are small chunks of the sample whose magnetic field points in a given direction. In an unmagnetized sample the domains are randomly oriented, so in the macroscopic view there is no net field since the norths and souths cancel one another. In a magnetized sample the differently oriented domains are coerced by an external field to point in a similar direction. This magnifies the field and is how permanent magnets are made.
In your question I'm not sure if its asking how moving charges make fields at the atomic level, or how the atomic level of the sample will react to current moving through it. The latter was described above, a current makes a field, the domains respond. The former is a bit trickier but I'll try to make it make sense. The essence of that question is "how can an atom have a magnetic field?" I'll give you a classical (not quantum) answer. Electrons can be thought of as orbiting a nucleus. This is analogous to an electric current going around a loop of wire. Just like the loop of wire a current makes a magnetic field. This is done in the outer valence of the atom. If the arrangement of electrons is just right in an atom (like in iron) it will have an inherent, built-in field. Align all of these on way and you've got a magnet.