1. The problem statement, all variables and given/known data Use the Biot-Savart Law to find the magnetic field strength at the center of the semicircle in fig 35.53 2. Relevant equations Bcurrent=(μ/4π)*(IΔsXr^)/r2 Bwire=μI/2πd 3. The attempt at a solution The solution from the back of the book is B=μI/4πd It looks like they just added the two wires together and the the B-field of the loop in the middle is zero. I don't understand what the cross product would give you zero though. The example that derived the B-field of a wire put a point on the y-axis and used that to find R and determine the cross-product. Why would that lead to a cross product of zero for the arc?