magnetite powder tip - magnetic force?

[kinny]

Hi

I am designing a solenoid to interact with a magnetite-powder tip. I can't find specifications about the magnetite I am using, and properties seem to depend on factors I don't know. Could you give me a rough estimate (just order of magnitude is fine) of the force given a certain magnetic field B of the solenoid and a tip of area pi*(0.2mm)^2 covered in magnetite powder?

Thank you
Cristina

 

[MagBen]

since the permeability of magnetite is hundreds (if not thousands) of times higher than air, you can treat it as steel. in this case, the pulling force F = .577 x B^2 x S
B- the flux density at the magnetite tip (not the B inside the solnoid which should be larger than B at a distance to the tip), unit: KG
S-area of tip in square inch
F - force in lb
Assuming B = 5kG, F = .577 x 5x5 x 3.14 (.2/25.4)^2 = .0028 lb
assuming B = 10 KG, F=.011 lb.

You can see the challenge is to get the B which is closely related to the gap between the tip and solenoid.