Deriving the circuit approximation of a magnetic circuit

[squelch]

Homework Statement

For the magnetic circuit:
Derive the circuit approximation.
Compute all magnetic fluxes if the total solenoid current is I.

Homework Equations

R_m = L / μS

The Attempt at a Solution

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Mostly, right now, I'm just trying to determine the magnetic circuit equivalent. From there it seems like simple circuit analysis. (Note that in my recreation of the diagram, I failed to add in the small L5 annotated at the top right of the larger subcircuit).

Is my intuition correct in treating the different media as a parallel of three resistances? This one is a bit strange, I can't find any solid worked examples of this type with differing media.

edit: The two resistances Rg1 and Rg2 represent the air-gap.

 

[nilesh_pat]

For the circuit approximation, it can be treated as a parallel of three resistances Rm, Rg1 and Rg2.The total magnetic flux can be computed using Ohm's law: Φ = I * (Rm + Rg1 + Rg2).