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Homework Help: Solenoids (Magnetism)

  1. Sep 7, 2009 #1
    1. The problem statement, all variables and given/known data

    A toroidal solenoid has a 60cm inner diameter and a 65cm outer diameter. The toroidal solenoid has 200 turns and carries a current of 30 Ampere. Determine the range of values for B inside the toroid.

    2. Relevant equations

    Ampere's law for toroid:
    B = Uo*N*I/2*pi*r
    where Uo = 4.7pi*10^-7

    3. The attempt at a solution

    as we are given inner diameter = 60cm and outer diameter = 65cm and since the law requires it in radius.. and as r = d/2 therefore inner radius = 30cm = 0.3m and outer radius = 32.5cm = 0.325m

    and we are given N as 200 turns and Current(I) as 30 Ampere's
    as we have to calculate the value inside B

    subbing all given values into the Ampere's law for toroid
    gives us (4PI*10^ - 7)(200)(30)/2PI(0.3) = 0.004T

    I'm not sure if this is correct? can someone help me out???

    thanks for the help :)

    Last edited: Sep 7, 2009
  2. jcsd
  3. Sep 7, 2009 #2


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    Looks OK, except I would use the average radius 0.3125 m.
  4. Sep 7, 2009 #3
    Thanks :) But is there any specific reason why you would use the average radius?
  5. Sep 7, 2009 #4


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    Now that I reread the problem, I see that you are asked to find the range of values, not some kind of average which is what I was proposing. :redface: You need to calculate two values, one for the inner radius and one for the outer radius. That should give you the range of values. :wink:
  6. Sep 7, 2009 #5
    ah awesome... Thank you :)
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