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What's the magnetic field?

  1. Jul 9, 2009 #1
    1. The problem statement, all variables and given/known data
    A straight wire carrying a current of 42 A lies along the axis of a 6.6 cm-diameter solenoid. The solenoid is 70 cm long and has 250 turns carrying a current of 6.0 A.
    Estimate the magnitude of the magnetic field 4.2 cm from the wire.


    2. Relevant equations
    magnetic field due to a straight current I
    B = mu_0*I/(2*pi*r)


    3. The attempt at a solution
    Note 4.2 cm > radius 3.3 cm, so the point is outside the solenoid, the magnetic field is only due to the straight current
    use I = 42 A, r = 4.2 cm, get B = 0.20 mT
    Anything wrong?
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Jul 9, 2009 #2

    rock.freak667

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    Homework Helper


    The solenoid carries a current, so it has a magnetic field. For a solenoid

    [tex]B=\mu_0nI \ where \ n=\frac{No. \ of \ turns}{Length \ of \ solenoid}[/tex]


    So you'd need to find the resultant mag. field of the solenoid and the straight conductor.
     
  4. Jul 9, 2009 #3
    B = μo(N/l) * I = μonI
    is only valid for magnetic field INSIDE the solenoid.
    The field OUTSIDE the solenoid is zero.
    So the field is only due to the straight current
     
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