Hi, I'm having a problem with the exercise attached.

I can't understand how the lengths given in the table were calculated. I know that length Rg is 2mm, my reasoning for Rc2 is that it has to be in the middle of 2cm so that's why it equals 1, and since Rc1 is in the bottom its length will be 8-1=7 cm. Is that reasoning correct?

However I have no idea why length Rb is 5cm. To be honest I don't even understand what is reluctance Rb in this circuit and where does it come from?

Also what are these surfaces S given in the table and how were they calculated?

Thank you for any help

 

Hi,

Did you try using 1/2 of the width of each area to try to come up with the mean path?
First you have to find the mean path.