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Homework Help: Solving for magnetic field from a solonoid

  1. Jul 27, 2011 #1
    1. The problem statement, all variables and given/known data

    The figure below shows a Helmholtz coil used to generate uniform magnetic fields. Suppose the Helmholtz coil consists of two sets of coaxial wire loops with 17 turns of radius R = 76.6 cm, which are separated by R, and each coil carries a current of 0.131 A flowing in the same direction. Calculate the magnitude and the direction of magnetic field in the center between the coils.


    2. Relevant equations

    Isn't this a simple solonoid? So can't you just plug in the numbers and get the answers? Or does the multiple connections change the problem?

    B = u_0*i*n
    n = N/L

    3. The attempt at a solution

    B= (4*pi*10^-7)*0.131*n
    It says r is equal to the length. so, n = N/L = 17/0.766

    B= (4*pi*10^-7)*0.131*17/0.766
    B = 3.653*10^-6 T, but this is wrong. Can anyone point me in the right direction?
  2. jcsd
  3. Jul 28, 2011 #2
    For this problem yo are trying to calculate the field between the coils. The formula you are using for a solenoid is therfore not valid as it is only valid in the cenetre of a long solenoid. Try treating each coil as a loop of wire of N turns.
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