Formulas for designing an electromagnet with a specific repulsive force at 25mm

[amdam]

I want to design electromagnet for my project. I want to know which formulas are used while designing electromagnets and methodology if we know repulsive force we require at a distance of 25mm from one end of electromagnet.

 

[CWatters]

Look up Maxwell's Force Formula and perhaps see the links below under "Similar discussions..."