I say in this situation the center electron will not go to surface (because there is no force)and it is against law that charge in conductor will be always in surface

thanks that M make it clear , the book I was reading did not mention that and I was confused what the ... is just happened there

put a winding (with no core) in vacuum ,i have I , N , L so H is known , B is known so μ = B/H. it is measured without my choice so there is something there

I understand this but when we wants to describe μ in a ferromagnetism (why and how μ work) we use the its molecule arrangement . I did not understand how in vacuum we could describe why and how μ0 work?

but refraction index is a compare between two thing not a real thing , electromagnetism Permeability is a property of something. we give refraction index = 1 to vacuum but Vacuum permeability = 4p * 10^-7 . it is something that measure independently .