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# Physics/Magnetism

Question
QUESTION: Sir,
Now I'll ask you a question that is a simple curiosity of my mind. As far as my remembrance goes, we were introduced to the basic concepts of magnetism in the sixth grade and since then I have this doubt in mind. It is this: Why does a magnet attract any object say an iron nail? At some website I have found that a pole of the magnet induces an opposite polarity on one side of the iron nail. But I am not satisfied. This is because I ask why not any other object induce the polarity. Please help me out.

ANSWER: Many types of atoms have magnetic moments (meaning that they are, themselves, very tiny magnets).  Sometimes these magnets tend to line up against one another (as larger magnetic materials do, north ends attract south ends and they line up N-S, S-N.  Some of these atoms can have the directions of their magnetic fields altered by applying a very strong external magnetic field, like iron.  In those materials with very strong internal magnetization (a complex subject beyond the scope of this forum), the polarization of the internal magnetization can exist in random directions called domains.  Those directions can be changed with the external field so that the material forms a net north and south pole.  The north pole will be closer to whatever made the externally applied field that corresponds to its south pole.  These will attract.  So if you bring the south pole of a magnet near some iron, it will form a north pole on the end closes to it, and the north pole will be further away.  Because of the dependence of attraction on distance, there will be a net attraction.  The same (opposite polarities) happens when you bring the north pole near a piece of iron, again resulting in a net attraction.  There are many different magnetic behaviors of different atoms and molecules.  Some have nearly no net internal magnetic moment, so are pretty non-magnetic.  Some align with themselves locally very strongly and are not really affected by externally applied fields.  Some have electronic structures that cancel out the effect.  Other weird ones actually repel a magnetic field weakly, but those are rare and there are complex quantum effects to consider.

---------- FOLLOW-UP ----------

QUESTION: Sir ,
Could you please explain me how come  atoms have magnetic moments? As for your answer it made me feel the satisfaction of ages.

This is a complex subject that gets into quantum mechanics, but I'll give you a basic idea.  Every electron that fills up an orbital has both a spin and an angular momentum.  When a charged particle has spin and/or angular momentum it is like a current flowing around in a wire, which creates a magnet.  That gives it a magnetic value based on its angular momentum and charge...we call that its magnetic moment.

Physics

Volunteer

#### Dr. Stephen O. Nelson

##### Expertise

I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

##### Experience

I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Education/Credentials
Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.