Re: How does the permeability of the armature affect the speed of rotation of a motor
Permeability is dependent on the formation of a magnetic field in the material.
Think about it like this. The more permeable the material is, the more ability it has to form a magnetic field.
So how do motors work? Well you should know the motor effect already as I'm assuming that you are looking at the speed of rotation of a motor. I think you can understand now why the permeability of the armature makes a difference. The more permeable the material is, the more efficient it is as a motor. This can have certain downfalls though but that isn't in the scope of the syllabus so I'll leave it there (actually permeability is NOT in the syllabus so you don't even need any of this info about it in itself).
In saying that, you could use permeability as a means to understand why having a wooden armature would not work and a wiring armature would do much better instead.