# Physical interpretation of Reluctance

1. Oct 3, 2004

### cosmonova

Hi,

I would like to know what is the physical interpretation of magnetic reluctance.
Also, I would like to know why should the magnetic flux in a magnetic circuit composed of different magnetic materials and subject to a magnetomotor force should be the same?

Thank you.

2. Oct 3, 2004

### Clausius2

First of all, If you post your doubt in the Electrical Engineering forum, surely you will have better answers (more accurate).

Secondly, If there is some electrical engineer somewhere and I say something wrong, excuse me.

Thirdly, I'm going to try to remember my days of Electric Machines studies:

$$R=\frac{L}{S\mu}$$

The Reluctance is the resistance showed by a Magnetic circuit to the pass of the magnetic flux.

L is the lenght of the magnetic path, the longer the path the greater the resistance. S is the cross section of the magnetic path, the wider the section the less the resistance. And $$\mu$$ is the magnetic permeability. Substances like Air of low permeability, makes greater the resistance (the gaps inside transformers and electric motors acts increasing the reluctance).

The physical interpretation is viewed better comparing the two similar laws:

$$F=Reluctance*\phi$$ where F=Electromotive Force; $$\phi$$=magnetic flux. This is the Hopkins Law.

$$V=Resistance*I$$ Ohm's Law.

Both are similar but one is employed with electrical circuits and the other with magnetic circuts. The rest is left to your imagination .