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Homework Help: Two long wires carrying current

  1. Dec 19, 2014 #1
    1. The problem statement, all variables and given/known data
    Two long wires carrying current I1 and I2 in opposite directions pass through a closed path S as shown in the picture.
    What are the values of ∫B⋅ds and ∫E⋅ds if:
    i) I1=I2=1A
    ii) I1=1A and I2=0A?


    2. Relevant equations
    Ampere's Law: ∫B⋅ds=μ0I
    Faraday's Law: ∫E⋅ds=-dΦB/dt

    3. The attempt at a solution
    For i, ∫B⋅ds=μ0(I1-I2)=μ0(0)=0
    For ii, ∫B⋅ds=μ0(I1)=μ0(1)=μ0

    Is these correct? But I have no idea of finding ∫E⋅ds

    Please help.
  2. jcsd
  3. Dec 19, 2014 #2


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    2017 Award

    What about the righthand side if you knw the currents are constant ?
  4. Dec 20, 2014 #3

    rude man

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    What is Φ for your situation? Hint: it doesn't matter whether the currents are constant or time-varying.
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