Permeability

Many materials, which conduct magnetic flux, tend to be metal based, for example soft iron .

The flux density of a substance under a magnetic field is determined by its magnetic permeability.

Permeability

Indicates how easily magnetised any material is, for example.

Air has a permeability of 1.
Soft iron's permeability is far greater than that of air.

Reluctance

Is the resistance offered to the passage of magnetic lines of force through a substance. Fig 9 illustrates basic behavior when glass or iron is placed near a magnet. Fig 9

Fig 9 A illustrates the basic field surrounding a magnet
Fig 9B a piece of glass inserted into the path of the field has no effect

Fig 9a

lines of magnetic flux through glass

Fig 9b