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

• dhqpwoe

## Homework Statement

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.

## Homework 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

## 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!

Is the solution key wrong? (Should I be integrating from s to s+a?)