MadSci Network: Physics

Re: how can i calculate the force two electromagnets pull each other?

Date: Fri Feb 2 15:11:15 2001
Posted By: Dr. Fred Jeffers, Staff, Magnetic Recording Research, Iomega corp.
Area of science: Physics
ID: 979233049.Ph

  Calculating the force between two magnets is very difficult in detail.  If
the magnets are free to rotate, the force is given by the magnetic moment of
magnet #1 times the rate of change of the field of magnet #2.  Reversing the
labels on the magnets has no effect on the force.  At distances larger than 
or 3 times the size of the magnet, the field varies as the inverse cube of 
distance.  Hence the force varies as the inverse fourth power.  This is why
magnets do not exert much force until they are close together.  A factor of 
increase in the separtation lowers the force by a factor of 16!
     Calculating the force when the magnets are close together or when they 
not free to rotate requires a very comlicated computer program.

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