I'm having some trouble withe the following problem.

For the above circuit I need to

a) Draw the magnetic equivalent circuit.

b) Compute the flux density in the working air gap for x=10 mm.

c) Compute the value of the energy stored in Wfld (for x=10 mm).

d) Compute the value of the inductance L (for x=10 mm).

e) For a force ffld of 1000 N determine for x=10 mm the current I=I0 required.

given

grad = 1 mm, R=20 mm, and d=10 mm. The exciting coil has N=1000 turns and carries a constant current of I=10A.

My main problem at this point is actually part 'a'. This circuit is quite different to ones analysed in my lecturers and my text book hasn't got anything on it either. Is this a common configuration?

I can't really see how the windings work in this case. Could someone explain what is going on with that? If its not to much trouble, a diagram would be much appreciated.

thanks a lot guys