Hello,

I need to calculate/estimate the force between a solenoid electromagnet and a piece of iron on a certain distance from the magnets airgap, preferable in a simple way under ideal conditions rather than a very exact calculation.

I have found the following formula at a couple of places (for example at:

http://www.ehow.com/how_5969962_calc...omagnet.html):
Force = ((N x I)^2 x k x A) / (2 x g^2)

N = the number of turns in the solenoid

I = the current, in amperes (A), running through the solenoid

A = the cross-sectional area, in meters-squared, of the solenoidal magnet

g = the distance, in meters, between the magnet and the piece of metal

k = 4 x pi x 10^-7 (a constant)

However I am a bit confused, as the formula do not contain any variable defining the metal object size or mass, surely the mass of the metal object as well as the material must have an impact on the force between the object and the magnet? Or what "force" is actually calculated in this formula?

Any ideas?