[TheForge]magnet Q.

[Steve Smith]

The temperature when magnetism goes to zero is the Curie temperature, 
and is sometimes used by some folks in hardening steel. The decrease in 
magnetism is continuous as the temp is approached, it doesn't happen all 
of a sudden. At some temperature below the Curie point, you magnet on 
the door won't be strong enough to hold itself up.

For a magnet to be magnetic, all (well, most of) the little microscopic 
magnetic regions (domains) need to be pointing in the same direction 
(north, south). As the temp increases, the domains wobble more and more, 
when they wobble enough, they flip and randomize, removing the 
magnetization (NSNSNS instead of NNNNN).

Hope this makes sense.
Steve Smith

Roger Olsen wrote:

> Hey Andy,
> 
> Ask your friend one other thing about magnets.  I wonder about heat, at what
> point does it drain a magnet of its magic affects?   I have never used them on
> fire doors but I know many have.  I have considered using them in the past and
> I am sure I will again in the future.
> 
> If I did I would use the 'Rare Earth Magnets' sold by Lee Valley and others as
> well.  They seem to be about 10 times stronger than the radio shack type
> magnets.
> 
> Roger Olsen
> __________________________________
> 
> Gladish Family wrote:
> 
> 
>>>1. I have a number of assorted magnets used for set-ups, mock ups and
>>>the like...should they be stored separately, carefully aligned
>>>north/south, to retain max  pull ( suck?) or is it not a problem just to
>>>toss them in a box with their friends?
>>
>>My understanding is that magnets are manufactured by applying overwhelming
>>magnetic fields (i.e. really really huge!) to a previously neutral chunk of
>>metal, and that heat or overwhelming magnetic force are the only ways that
>>magnets lose their pull, other than physical deterioration.
>>I have a friend who sells magnets for a living- I'll ask him.
>>Andy G.
>>
>>_______________________________________________
>>Manage membership or unsubscribe at:
>>http://mailman.qth.net/mailman/listinfo/theforge
>>theforge mail list group photo site is
>>http://www.photoaccess.com
>>Login:  blacksmithblacksmith at hotmail.com
>>password:  anvil
>>___________
> 
> 
> _______________________________________________
> Manage membership or unsubscribe at:
> http://mailman.qth.net/mailman/listinfo/theforge
> theforge mail list group photo site is
> http://www.photoaccess.com
> Login:  blacksmithblacksmith at hotmail.com
> password:  anvil
> ___________
> 
> 
>