Question about magnetizing field and recoil permeability

[trini]

Hey everyone, I'm trying to work out the current I would require to produce a 44kOe magnetizing field in a radial solenoid. From my understanding, in order to do this I need the relative permeability of my material, the inductance of my coil, as well as the number of turns in the coil and it's length.(I'm not sure if i am supposed to use the recoil permeability here but it seems to me to be the correct option)

Now:
μ_rec = 1.22
relative permeability, Κ_m = μ_rec/μ₀
length of solenoid,l = 0.166116 m
turns, N = 600
Average loop area, A = 0.03246941 m²
H = 44000 G = 3, 501, 409 Am^-1

integral H.dl = μ0.Κ(I_pen + dΦ/dt) [recall: dΦ/dt = -ε₀LI][I_pen = (N / l) I]
3, 501, 409 = (μ₀)(μ_rec/μ₀){(N/l)I - Aε₀(N²/l)I}
3, 501, 409 = μ_recI {(N/l) - Aε₀(N²/l)}
3, 501, 409 = (1.22) I {(600/0.166116) - (0.03246941)(8.85418782 × 10^-12)(600²/0.166116)}
3, 501, 409 = 4406.559271 I
I = 794.5902 AEDIT: I just realized i forgot to multiply the inductance by ε₀! This current seems more correct, could someone please verify though?

 

[trini]

I didn't want to start a new topic, but i also have another question for you guys, is there any hollow permanent magnet(not necessarily closed, more like a hollow pipe) which exists such that the inner surface is one pole and the outer surface is the opposite pole?

 

[rl.bhat]

I didn't want to start a new topic, but i also have another question for you guys, is there any hollow permanent magnet(not necessarily closed, more like a hollow pipe) which exists such that the inner surface is one pole and the outer surface is the opposite pole?

Yes. Inside the DC motor of tape recorder, armature is housed in the hollow permanent magnet.