Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: that mad man on 03/06/2007 18:02:25

Title: magnetizing an iron nail
Post by: that mad man on 03/06/2007 18:02:25

I think most peoples know how to magnetize an iron nail using a magnet, obviously the nail becomes magnetised but what happens internally to the nail when I do that. 

What am I doing to the iron?
Is the magnet changing the structure of the iron and rearrangeing its atoms?
Does the magnets magnetism get weaker as the iron gets magnetised or is there no change in the magnet?
How come I create 2 poles on the iron and yet only used one to magnetise it?


Bee

Title: magnetizing an iron nail
Post by: DrDick on 03/06/2007 19:40:55

I'm not an expert on magnetism, but this is my understanding of it.

Each atom is a little magnetic.  As these atoms agglomerate, they form crystals in which the magnetic fields are lined up.  Then the crystals get together, but not necessarily aligned with respect to the magnetic field.  A normal piece of iron has a random distribution of magnetic fields, so is not magnetic.  Putting this piece of iron in a magnetic field will align some of the crystals.  At higher temperature, the alignment occurs to a greater extent.

You can't have a magnet with only one pole, just like you can't have a planet with only one pole.  Having one implies the presence of the other.  A magnet is just an item with a magnetic field that extends from one pole to the other.

Dick

Title: magnetizing an iron nail
Post by: DoctorBeaver on 03/06/2007 20:53:31

I'm sure I've heard certain Big Bang theories that involve the creation of magnetic monopoles  [???]

Title: magnetizing an iron nail
Post by: that mad man on 03/06/2007 21:30:25

Hi Dick.

For some strange reason (maybe schoolboy science) I thought heating a magnet destroyed its magnetism or made it weaker?.mmmm.

@ DoctorBeaver, hehe you're in front as that's just what this loose research is about.  [;)]

Bee

Title: magnetizing an iron nail
Post by: DrDick on 03/06/2007 22:24:38

Quote from: that mad man on 03/06/2007 21:30:25

Hi Dick.

For some strange reason (maybe schoolboy science) I thought heating a magnet destroyed its magnetism or made it weaker?.mmmm.

@ DoctorBeaver, hehe you're in front as that's just what this loose research is about.  [;)]

Bee

In the absence of an external magnetic field, it will.  The point is that higher temperature allows the material to change to what it wants to be.  In the presence of a powerful external field, the crystals will tend to align with that.  In the absence of that field, each crystal will have the tendency to align nearby crystals in the opposite direction, resulting in a canceling out of the net field.

Dick

Title: magnetizing an iron nail
Post by: that mad man on 04/06/2007 20:55:41

Thanks Dick.

I should have remembered, when molten rock cools it has an imprint of the magnetic field around. One of the ways you can tell if rocks are in their original position or not.

Bee