MadSci Network: Physics

Re: does magnetism become less when magnets are used?

Date: Thu Nov 18 13:29:28 2004
Posted By: Dan Patel, Graduate Student, Chemistry
Area of science: Physics
ID: 1099194246.Ph

When two magnets are forced together, their magnetization may diminish 
over time, or it may stay the same.  This depends greatly on how strong 
the magnets are.  If you take a strong magnet (what is termed a “hard 
magnet”) and place its north pole next to the north pole of a weaker 
magnet (termed a “soft magnet”) the soft magnet’s magnetization will then 
decrease and eventually change to match the magnetization of the hard 
magnet.  The amount of time that is required for this change depends on 
how well the domains in the soft magnet are aligned.  The reversal occurs 
because the direction of magnetization of the individual domains in the 
soft manget begins to change in order to match the net magnetic moment of 
the hard magnet.  Of course, this is a simplified explanation.

To learn more about these processes, I would recommend consulting “The 
Physical Principles of Magnetism” by Allan H. Morrish or the following PDF 
document available online to learn more about the basic principles of 
magnetism (

I don’t know much about the two devices you spoke of (the Minato Wheel and 
Perendev device).  From what I was able to learn, it 
appears as though simple magnetic forces are used to drive a motor 
id=EplkEulpVAzZVHajZo and
)for both devices.  If the magnets used are permanent 
magnets (that is, hard magnets) and the magnetic forces they are subjected 
to are not extreme, then in theory the strength of these magnets maintain 
their magnetization over time.  In practice, though, heating causes 
magnets to weaken over time, and I would guess that the same would happen 
in these motors and so the devices would have some useable lifetime after 
which the magnets would need to be replaced.

Current Queue | Current Queue for Physics | Physics archives

Try the links in the MadSci Library for more information on Physics.

MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci

MadSci Network,
© 1995-2003. All rights reserved.