Question about magnetizing field and recoil permeability

1. Jul 6, 2009

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:
μrec = 1.22
relative permeability, Κm = μrec0
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(Ipen + dΦ/dt) [recall: dΦ/dt = -ε0LI][Ipen = (N / l) I]
3, 501, 409 = (μ0)(μrec0){(N/l)I - Aε0(N2/l)I}
3, 501, 409 = μrecI {(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 A

EDIT: I just realised i forgot to multiply the inductance by ε0!! This current seems more correct, could someone please verify though?

Last edited: Jul 7, 2009
2. Jul 7, 2009

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?

3. Jul 7, 2009

rl.bhat

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