sci.physics.electromag

On Feb 29, 12:48=A0am, Benj wrote:
> On Feb 28, 6:13 pm, Mike D wrote:
>
> > The quickest way to get an answer to 1 is to use one of the online
> > calculators. =A0For example:http://www.dextermag.com/CalculationList.asp=
x
> > Neo45 will have a Br of approximately 1.37 Tesla (13,700 Gauss)
>
> > For 2: The field generally drops as a function of the square of the
> > distance
>
> > For 3: The same webpage above will give you a reasonable approximation
> > of the field between two magnets (although admittedly on a steel
> > yoke).
>
> Hey, Thanks! That online calculator sure is nifty! In playing with it
> I see that the main parameter is the Residual B of the magnetic
> material itself. =A0Like I suspected since the lifting force depends on
> area it sort of cancels out. Also in trying different size magnets I
> found that the field is always the same at the center of the surface
> for all magnets of proportional shape! =A0Like say 1 x1, .5 x .5 and .25
> x 25 etc. in cylinders. =A0This is exactly what I was looking for!
>
> Now I'm wondering what the calculation is they are doing? That the
> trouble with online calculators, you sometimes have trouble figuring
> out is being calculated. Wonder if the source in the html...?
>
> great site! Thanks.
>
> ...And now to build that perpetual motion free energy machine! =A0 (just
> kidding!)

The calculation just uses an analytical approximation that is accurate
enough for most applications. You can find the actual equations used
in the design manual (page 27) in :
http://www.dextermag.com/uploadedfiles/Reference_Design_Manual.pdf

Best regards,
Mike