# The force and torque between two permanent magnets?

Hi all =)

I am interested to find the forces and torques between two (diametrically magnetized) cylindrical permanent magnets (PMs) placed within a vicinity, as shown below:

The NdFeB PMs placed beside one another with a distance, d. Both are rotated by independent external sources (I have solenoids to independently drive the PMs). This will affect each PM in terms of the torque and force.

So I am just wondering if I could use the same force/torque equations (e.g. for the force as shown below) between two axially magnetized PMs for the diametrically magnetized ones as well:

I do not have a software for this, thus I would need to model it mathematically.. (i have spent weeks trying to find a way to do it but I ran out of idea)

I see that most cases are calculated for axially magnetized PMs so I am not sure if the generally available equations for the axially magnetized PMs can be used in my case. I got pretty confused as to how I should compute the dynamics (force and torque of one PM (primary) when another is closely present).. as well as how far should the PMs be apart so I could ignore the effect of the other PM onto the primary PM.

Looking forward to hearing from anyone with ideas and advice =) Thank you very much!

Dr. Courtney
Gold Member
2020 Award
Thanks, Dr Courtney. Seems like FEM is the best way to approach problems like this?

Dr. Courtney
Gold Member
2020 Award
Experiment is the best way. FEM can be tricky, and results must be validated to be reliable.

I have some hall effect sensors which could help get the magnetic field at a certain location..I could use that for force or torque verification through my equations. Do you have any suggestions on what sensors or equipment I could use in experiments as such? Thanks again~! =)

Dr. Courtney