MadSci Network: Physics

Re: Can you incresed the power of a magnet by adding more to the system?

Date: Mon Mar 29 09:58:00 1999
Posted By: John Balbach, Post-doc/Fellow, Physics, National Institutes of Health
Area of science: Physics
ID: 922138820.Ph

     There are two issues that your question addresses.  Can the power of 
an individual magnet be changed, and do two (or more) separate magnets add 
their power together?
     I will assume that you are asking about permanent magnets, like bar 
magnets or refrigerator magnets.  Permanent magnets have internal domains, 
which are regions of aligned magnetic dipoles.  These dipoles are the atoms 
of the magnet.  When a permanent magnet is magnetized, what happens is that 
one of the domains grows larger than any of the other domains.  The power 
of the magnet depends on how much of the magnet is part of this largest 
domain, so there is an upper limit to the power of a single magnet, but it 
can be varied below that.
     Two separate magnets can combine their power to create a more powerful 
magnet, but as you have probably noticed, combining two magnets to add 
their power is not easy.  The magnets will (usually) want to combine so 
that the power is lower, but it is possible to hold them in some sort of 
framework, so that the powers add in the way that you want.
     I hope that this has answered your question.  If you want to read more  
about magnets, you should know that the word "power" has a very specific 
meaning in physics, and we have used it incorrectly here.  The quantity 
that is used to describe the strength of magnets is called the "magnetic 
moment" or sometimes "magnetic dipole".

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