### Re: Is there a formula to calc. the force b/w repelling magnets using distance?

Date: Mon Mar 1 18:30:04 2004
Posted By: Dr. Fred Jeffers, Staff, Magnetic Recording Research, Iomega corp.
Area of science: Physics
ID: 1073337984.Ph
Message:
```
I can't imagine why this question was sent back to you.  I never saw
it.
If the magnets are free to rotate to be parallel to the local field,
the force between two magnets, say Magnet 1 and Magnet 2, varies as the
magnetic moment of Magnet 1 times the derivative of the field of Magnet
2.  If the magnets are not free to rotate the situation is quite
diffrerent and a lot more complicated.  Some vector calculus is needed.
At a distance large in comparason to the size of the magnets, the
field from Magnet 2 is an inverse cube.  Hence the derivative (rate of
change) of the field is an inverse fourth power.  This sort of drastic
distance dependance is outside ones usual experience and that is why
people get pinched when fooling with large NdFeB magnets.

```

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