Total charge through point on wire due to changing current on other wire

  1. 1. The problem statement, all variables and given/known data
    A square loop, side a, resistance R, lies a distance s from an infinite straight wire that carries current I. Now someone cuts the wire, so that I drops to zero. In what direction does the induced current in the square loop flow, and what total charge passes a given point in the loop during the time the current flows.

    2. Relevant equations
    Integral{B dot dl} = mu_0 * I => B=mu_0*I/(2*pi*r)

    emf=-d(Integral{B dot dA})/dt
    emf=I_induced*R

    3. The attempt at a solution

    I say that the flux is mu_0*I*a/(2pi)*Integral(dr/r) where r goes from s to s+a. The solution key agrees with me except for on the limits, which it says are a to 2a. I'm hoping that I am right for the problem as written and that the problem statement should have the square be a distance a (not s) from the wire... Does this sound right, or am I altogether wrong?
    Thanks!
     
  2. jcsd
  3. Is the solution key wrong? (Should I be integrating from s to s+a?)
     
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