hi everybody. the question is simple: what's the formula to calculate attraction force of an electromagnet (in newtons) ? other question: has repulsion force between two magnets, the same value that attraction force between those same magnets?
The answer to the second question is yes, provided the N and S poles of a given magnet are shaped the same way.
The answer to the first question is not as simple as you would hope. It depends one whether the magnet is a horseshoe magnet, a bar magnet, a solenoid, a toroid, whether there's a ferric core,...
PD
As a personally interesting anecdote, I was once responsible for the design, construction, and operation of a 250,000 lb iron-core toroidal magnet. I chose to instrument it with a Hall probe, embedded in a thin slot in one side. But the slot itself would disturb the field, which I had to account for. I proposed a linear model to calculate that, superimposing a piece of "negative iron" where the slot was, and calculating the total field of the magnet, against which I could compare the Hall probe measurement. This approach was deemed clever by my professors until a young post-doc pointed out to me, in a fatherly conversation in the hallway, that iron core magnets are nonlinear beasts and superposition doesn't work, a revelation that left me sick to my stomach. Sure enough, the Hall probe read values that were inconsistent with calculations and with the backup instrumentation. I ended up doing a very complicated lattice-relaxation calculation on a mainframe computer to compute the field.
PD
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