Question

What is the relation between the specific permeance of a differential path and the length?

(a) specific permeance of a differential path is directly proportional to the length

(b) specific permeance of a differential path is indirectly proportional to the length

(c) specific permeance of a differential path is directly proportional to the square of the length

(d) specific permeance of a differential path is indirectly proportional to the square of the length

I had been asked this question during an online interview.

Asked question is from Specific Permeance & Calculation of Magnetizing Current in chapter Principles of Magnetic Circuit Design of Design of Electrical Machines

Answer 1

Right choice is (b) specific permeance of a differential path is indirectly proportional to the length

For explanation I would say: The specific permeance is defined as the permeance per unit length. It is indirectly proportional to the length.