Magnetic equivalent circuit question

[theone]

Homework Statement

The question is to draw a magnetic equivalent circuit for this
http://postimg.org/image/kek5fgr9z/

Homework Equations

The reluctance is given by
$R=\frac{l}{μ_oμ_rA_c}$

The Attempt at a Solution

I am confused about the dimensions of the circuit, and also about what dimensions to use for the cross section $A_c$

For example, is the reluctance R1 given by

$R_1=\frac{\frac{60}{1000}}{μ_0 1500 (\frac{20}{1000} \frac{20}{1000})}$

 

[Hesch]

The question is to draw a magnetic equivalent circuit for this

Draw an electric equivalent, substituting the (magnetic) bars by (7) resistances. N1 can be substituted by a current source, N2 by an amp-meter.

 

[theone]

Draw an electric equivalent, substituting the (magnetic) bars by (7) resistances. N1 can be substituted by a current source, N2 by an amp-meter.

but I did that in the attachment. I wanted to check if the dimensions I'm using for $A_c$ is correct

 

[Hesch]

Sorry, I didn't see the attached.

Yes, A_c = 20 * 20 mm².

What are these ±O symbols meant to be? And why are there two? Are two currents induced in the "transformer" at the same time?

 

[theone]

What are these ±O symbols meant to be? And why are there two? Are two currents induced in the "transformer" at the same time?

the mmf from the wounded coil. I'm not sure what the correct symbol is
Shouldn't there be two? $N_1i_1$ on the left and $N_2i_2$ on the right

 

[Hesch]

the mmf from the wounded coil. I'm not sure what the correct symbol is
Shouldn't there be two? N1i1N_1i_1 on the left and N2i2N_2i_2 on the right

I don't know anything about american symbols ( I'm from Denmark ), but you must have different symbols for a current source/a voltage source. As suggested in #2, I'd use a current source because of the analogy between electrical current and magnetic flux.

I don't know if there must be one or two current sources, for example: Is N2 loaded/current supplied? I just know:

The question is to draw a magnetic equivalent circuit for this

 

[theone]

I don't know anything about american symbols ( I'm from Denmark ), but you must have different symbols for a current source/a voltage source. As suggested in #2, I'd use a current source because of the analogy between electrical current and magnetic flux.

I don't know if there must be one or two current sources, for example: Is N2 loaded/current supplied? I just know:

I forgot to mention that in addition to drawing a magnetic equivalent, the question also asked to find all the reluctance's.

On my diagram there are 4 reluctance's. But the solution only lists three reluctance's : 0.212, 0.292, 0.159 MA/m.

The 0.159 MA/m I can get as $R_4$,

$R_4=\frac{\frac{60}{1000}}{μ_0 1500 (\frac{10}{1000} \frac{20}{1000})} = 0.159 MA/m$

But I don't know how they got the other two.

 

[Hesch]

I guess that they have reduced the circuit into 3 reluctances:

a) R1+R2+R2 ( in series)
b) R1+R3+R3
c) R4

 

[theone]

I guess that they have reduced the circuit into 3 reluctances:

a) R1+R2+R2 ( in series)
b) R1+R3+R3
c) R4

thanks, I got it now