Which of the following statements with respect to reluctance are true?

(i) Reluctance is directly proportional to the length of magnetic circuit.

(ii) Reluctance is directly proportional to the area of cross-section.

(iii) Reluctance is inversely proportional to the absolute permeability of magnetic circuit.

The correct answer is option 2):

Concept:

• Reluctance is the property of a magnetic circuit of opposing the passage of magnetic flux lines, equal to the ratio of the magnetomotive force to the magnetic flux.
• The reluctance of the magnetic circuit depends on Length Area Nature of material
• The reluctance of a magnetic circuit is directly proportional to its length and inversely proportional to its cross-sectional area and its permeability.
• The reluctance is inversely proportional to the magnetic permeability of the material forming the closed path, directly proportional to the length of the path, and inversely proportional to the cross section of the path  Reluctance is inversely proportional to the absolute permeability of magnetic circuit.
• \(\Re = \frac{l}{{\mu A}} = \frac{l}{{{\mu _0}{\mu _r}}A}\)
• It is measured in A/weber so option (i) and (iii) is correct.