# Magnetism Problem

1. Apr 16, 2005

### confusion321

Which is the correct equation for Magnetic Reluctance ?

$$R$$ = Reluctance
$$l$$ = Length
$$A$$ = Area
$$\mu$$ = Magnetic Permeability of the material
$$\mu_0$$ = Magnetic Permeability of free space ($$4\pi \times 10^- ^7$$ tesla/ampere turn)

$$R = \frac {l} {\mu A}$$ as stated on Wikipedia or $$R = \frac {l} {\mu_0 \mu A}$$ as stated in my text book.

2. Apr 16, 2005

### Staff: Mentor

The Wikipedia formula looks correct. Are you sure your book isn't using $\mu$ to mean relative permeability (which is just a ratio)? (If not, the units would make no sense in your book's formula.)

3. Apr 16, 2005

### confusion321

Thanks very much that would be it. "Relative Permeability"