Question

A magnetic circuit has a 20 cm lenght core with a permeability of 0.005 Wb/(Atm). The coil has 250 turns, and draws 0.4 ampere. Determine the mmf of the coil

Answer 1

B = U N I

Answer 2

@Yahoo! , I think that that is actually \(B\), an approximation the strength of the magnetic field inside the solenoid.

Here's the magnetomotive force:
http://en.wikipedia.org/wiki/Magnetomotive_force
\(F=N\ I\) where \(N\) is number of turns and \(I\) is the current.