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Question about magnetizing field and recoil permeability

  1. Jul 6, 2009 #1
    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)

    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. jcsd
  3. Jul 7, 2009 #2
    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?
  4. Jul 7, 2009 #3


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    Homework Helper

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