[modeleng] Re: RE Magnetic Chucks going OT - sorry guys!
- From: peter.chadwick@xxxxxxxxxxx
- To: modeleng@xxxxxxxxxxxxx
- Date: Wed, 22 Feb 2006 14:34:27 -0800
John Paget said:
>When you remove the keeper the effect is to push you down the B-H curve.<
First question is why? I suppose if you think of it in electrical analogy
terms (which is how I managed to understand magnetics enough to pass ONC -
dear me, that WAS a long time ago!) you can imagine the keeper as a low
reluctance (low resistance) which maintains the flux density
(webers/sq.metre in MKS) for a given AT/m (voltage in electrical terms).
What I don't see is what causes the loss in AT/m when you remove the
keeper, since I imagine the magnet itself consisting of the aligned
magnetic domains, which I thought required some energy to disturb them -
such as hammering, heating etc.
I presume that a material with a very square B-H curve could show very
little effect, but I'm still puzzled as to why the domains 'disalign'
themselves. I can see why the hysterisis is a problem - incidentally, I
was taught that the hysterisis occurs because of the reluctance of the
domains to move readily.
Peter Chadwick (still puzzled in San Diego!)
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