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Just thinking aloud ... It is possible for a star to grow so large it collapses under it's own gravity. Along a parallel path (so to speak) when a conductor carries a current too large for it to sustain, it burns out.

Can a ferromagnetic object be imparted a field too strong for it? What happens then?

I would begin to guess the dipoles within the magnet can only be magnetized so far; a stronger field wouldn't have an effect. But surely the same argument could have applied to a wire conductor?

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In a ferromagnet the field is the result of the aligned elecron spins. Once the spins are all aligned the field cannot be made any stronger. You could put a piece of iron in an external field more powerful than the iron could generate on it's own, but it would no especially surprising effect, and when you withdrew the iron from the field you'd just be left with magnetised iron.

There isn't an analogy with conduction in a wire. The heat generation in a conducting wire is the result of conduction electrons scattering off phonons and defects in the crystal structure of the wire and transferring energy to it. By making the wie a perfect crystal and lowering the temperature to absolute zero you can make the wire conduct arbitrarily large currents. Actually I'm not sure the resistance falls to zero at absolute zero (NB I'm ignoring superconductivity here) but it gets very small.

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In other words, the only resistance equivalent faced by magnetism is the opposing electron spin - which eventually is overcome. Is this in order? – Everyone Nov 7 '12 at 18:44
I'm not 100% sure I get what you mean. The fully magnetised state of iron is actually the lowest energy state. It's just that there are kinetic barriers to iron settling into that state. – John Rennie Nov 7 '12 at 18:51
I'm not totally clear on it myself ... just a sense of dissatisfication. – Everyone Nov 11 '12 at 20:15

The magnetic interaction of iron with an external magnetic field is an interaction of dipoles.

The equivalent for the electric field would be a very good insulator set in a strong electric field. An insulator does not have free electrons floating on a fermi level, but all its atoms can display dipole and quadrupole and higher pole distortions. And that will be it. At some level though of electric field strength, electrons can be broken off their atoms and then the insulator starts conducting and may even burn up.

There exist no magnetic monopoles to get the equivalent effect in a bar of magnet.

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