Permanent Magnet and Electromagnet

I have been told that the magnetic field from an electromagnet, is basically incompatible with that of a permanent magnet of equal strength. Is this true? BILL.
- WILLIAM NEIL (age 70)
ENGLAND (UK)

I'm not sure quite what that "incompatible" means. Probably it means this. If you put a "permanent" ferromagnet in an electromagnet's field in the direction for which the interaction increases the energy, then the magnet's domains will mostly flip their orientations and point the other way, if the electromagnet's field exceeds what's called the "coercive field" of the ferromagnet. Usually the coercive field is weaker than the internal field of the magnet.

I can't think of any fundamental reason why that has to be true, and glancing at the data for some permanent magnets, it seems that it isn't always:  . So for some magnets you can put the magnet in a field equal to its own, pointing the wrong way, and still keep some of the magnetization.

Mike W.

(published on 01/17/2014)