The Naked Scientists

The Naked Scientists Forum

Author Topic: Do Magnets Run Out ?  (Read 12408 times)

Offline neilep

  • Withdrawnmist
  • Naked Science Forum GOD!
  • *******
  • Posts: 20602
  • Thanked: 8 times
    • View Profile
Do Magnets Run Out ?
« on: 29/01/2006 05:04:26 »
Greetings ,


   (1)......Do magnets (NOT electro magnets) lose their magnetivity ? (is that a word ?.hmmm..I suppose I mean magnetism, but I like my word too !)

..anyway...do they ?...does the magnetivity decrease at all ?

   (2)......Is a magnet with charisma a very sexy piece of metal ?

No need to answer No 2 :)

Thanks

Neil
Magnet Enquirer

Men are the same as women.... just inside out !!


 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
Re: Do Magnets Run Out ?
« Reply #1 on: 29/01/2006 10:43:33 »
I'm sure that, as a kid, I had a magnet that lost its magnetism so I would say yes.
If I remember rightly (it was a LONG time ago) I'd just found out that you could magnetise needles by rubbing a magnet against them. Little boy, magnet, mum's sewing basket - a recipe for mischief! But I'm sure that after I'd got all mum's needles & pins stuck together, my magnet died.
 

Offline Soul Surfer

  • Neilep Level Member
  • ******
  • Posts: 3345
  • keep banging the rocks together
    • View Profile
    • ian kimber's web workspace
Re: Do Magnets Run Out ?
« Reply #2 on: 29/01/2006 12:12:18 »
Ferromagnetic materials are such that the molecules natural magnetism is enough to cause them to align locally and form magnetic domains.  this ogccurs as long as the material is coo enough (below the curie temperature when natural atomic agitation prevents this

ferromagnets are formed wnen the naturally occurring magnetic domains in the material (usually crystal boundaries) are algined using an external magnetic field.

When this field is removed some of the magnitism reverts but there is a residual magnretism left.  "Hard" ferromsgnets have a large residual field.

Any disturbance vibration, stessing or heating of the material is likely to cause more domaind revert to random positions and the magnetic strength to fall.

Learn, create, test and tell
evolution rules in all things
God says so!
 

Offline daveshorts

  • Moderator
  • Neilep Level Member
  • *****
  • Posts: 2583
  • Physics, Experiments
    • View Profile
    • http://www.chaosscience.org.uk
Re: Do Magnets Run Out ?
« Reply #3 on: 29/01/2006 21:00:47 »
Yeah the molecules align, due to slightly mysterious quatum reasons rather than their natural magnetism. This is a local effect, so at a short range 2 atoms will be aligned, however working against this is that if you take a big magnet and bend it round in a circle you release a whole lot of energy (the N-pole at one end is attracted to the S at the oter), so if you look at a normal piece of steel the domains are arranged in lots of circles.
 If you apply an external field to a ferromagnet, the domains will tend to align with it, and in the right material they will stick there. However it can allways release energy by forming the little circles and loose it's overall magnetism.
 

Offline ukmicky

  • Moderator
  • Neilep Level Member
  • *****
  • Posts: 3011
    • View Profile
    • http://www.space-talk.com/
Re: Do Magnets Run Out ?
« Reply #4 on: 29/01/2006 21:36:47 »
quote:
Is a magnet with charisma a very sexy piece of metal ?


You must be talking about a babe magnet, and yes we/i do exist:D

Ps my wife just read what i wrote and walked away laughing at me, i didnt know magnets were funny:D

Michael                 HAPPY NEW YEAR                    
« Last Edit: 29/01/2006 21:58:25 by ukmicky »
 

Offline neilep

  • Withdrawnmist
  • Naked Science Forum GOD!
  • *******
  • Posts: 20602
  • Thanked: 8 times
    • View Profile
Re: Do Magnets Run Out ?
« Reply #5 on: 29/01/2006 21:41:05 »
quote:
Originally posted by ukmicky

quote:
Is a magnet with charisma a very sexy piece of metal ?


You must be talking about a babe magnet, and yes we/i do exist:D

Ps my wife just read what i wrote and walked away laughing, i didnt know magnets were funny:D

Michael                 HAPPY NEW YEAR                    



Wifey clearly does not find you attractive anymore !!:D

Strewth !!..I really said that didn't I ?...........sorry !![xx(]

Men are the same as women.... just inside out !!
« Last Edit: 29/01/2006 21:49:17 by neilep »
 

Offline ukmicky

  • Moderator
  • Neilep Level Member
  • *****
  • Posts: 3011
    • View Profile
    • http://www.space-talk.com/
Re: Do Magnets Run Out ?
« Reply #6 on: 29/01/2006 21:49:41 »
quote:
Wifeys clearly does not find you attractive anymore !!


Neil you are soooooo cruel, are you trying to say my wife has bad eyesight.:)

Michael                 HAPPY NEW YEAR                    
 

Offline neilep

  • Withdrawnmist
  • Naked Science Forum GOD!
  • *******
  • Posts: 20602
  • Thanked: 8 times
    • View Profile
Re: Do Magnets Run Out ?
« Reply #7 on: 30/01/2006 00:21:52 »
Well , you did say wifey read what you wrote (so she can plainly see very well)...looked at you. laughed and walked away... seems to me her eyesight is perfect !!:D:D

...anyway Michael...we all know you're a hunk !;)..espesh if you;ve got a 6 pack !!

Men are the same as women.... just inside out !!
 

Offline gsmollin

  • Hero Member
  • *****
  • Posts: 749
    • View Profile
Re: Do Magnets Run Out ?
« Reply #8 on: 30/01/2006 02:28:40 »
The permanent magnetism is usually stable, unless disturbed. The disturbance can be through heating above the Curie temperature, mechanical shock, or becoming de-magnetized by application of an external magnetic field.

"F = ma, E = mc^2, and you can't push a string."
 

sharkeyandgeorge

  • Guest
Re: Do Magnets Run Out ?
« Reply #9 on: 30/01/2006 10:53:48 »
a little off topic but can anyone explain why the magnetic poles are supposed to flip are they wearing out?

"Defender of the Sea"
 

Offline wim

  • Full Member
  • ***
  • Posts: 66
    • View Profile
Re: Do Magnets Run Out ?
« Reply #10 on: 13/02/2006 00:32:04 »
no it doesn't mean there running out (lucky us) it just happens every once in a while, it seems there also constantly "moving" those poles...

http://www.firstscience.com/SITE/ARTICLES/magnet.asp
 

Offline Atomic-S

  • Hero Member
  • *****
  • Posts: 928
  • Thanked: 18 times
    • View Profile
Re: Do Magnets Run Out ?
« Reply #11 on: 13/02/2006 05:57:20 »
In principle, ferromagnetism should remain indefinitely as long as there is not distrubing effects to disrupt it. Of course, it can be argued that disturbing effects are always present, in the form of thermal agitation, so that ferromagnetism will be lost eventually. But how fast?  Technically, diamonds also are continually reverting to graphite, and glass in window panes is continually flowing down onto the ground, both due to thermal effects; however in both cases the processes take so many millions of years that they cannot be observed on a human time scale. So, the question of whether ferromagnetism can be permanent can be asked either as a question in abstract theory (in which case the answer may be that neither it nor virtually anything else is permanent), or in practical terms, whether the process will proceed at a humanly observable rate. To the latter, we would have to say, "it depends."
 

The Naked Scientists Forum

Re: Do Magnets Run Out ?
« Reply #11 on: 13/02/2006 05:57:20 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums