If you consider this then there is no way to calculate F from B without including in your equations
atomic currents or electric charge...
Edit:
What about replacing permanent magnet with electromagnet with no core that produces equivalent B?
Equivalent electromagnet, but if we don't know N or I what is the overall description?
Something that measures in C*m/s .
A*m?
I"ve wondered the same thing myself. I wanted to calculate the force on a relay plunger, for instance, but I could never find an equation. And that despite I studied electro magnitism in college.
If in doubt, measure. Something like a relay plunger will depend a lot on the exact mechanical contruction so I don't think any calc will be worth doing.
Yes but he said "calculate the force on a relay plunger". Every relay I've seen had some type of iron frame on the coil, and the armature completes some magnetic path within the iron frame so you can't do a force calc based on the coil characteristics (ie; current, number or turns). You need to know all the characteristics of the mechanical construction including the iron frame and/or armature. Empirical measurement of the force is a much better option.