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Am I on the right track with Ampere's Law?

  1. Mar 29, 2009 #1
    1. The problem statement, all variables and given/known data
    A wire carries a current of 3 A in the downward direction. What is the magnetic field 2.0 cm away from the wire?

    2. Relevant equations
    ∫B·dl = µ0I

    3. The attempt at a solution
    So I pick a circle with radius 2.0 cm to go around the wire, and get

    B∫dl = µ0(3 A)

    ∫dl evaluates to 2pi(0.02 m).

    So B = [µ0(3 A) ] / 2*pi*0.02 m?
  2. jcsd
  3. Mar 30, 2009 #2
    That works, however the Biot-Savart law is easier to apply here and actually reduces to a formula identical to what you have written in the last line in the case of a long straight wire. B=µ0I/2(pi)r
  4. Mar 30, 2009 #3
    Thank you! I know the Biot-Savart law also works, I just wanted to make sure my concept of Ampere's Law was correct. =)
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