1. The problem statement, all variables and given/known data Two identical wires R and S lie parallel in a horizontal plane, their axes being 0.10 m apart. A current of 10 A flows in R in the opposite direction to a current of 30 A in S. Neglecting the effect of the Earth's magnetic flux density calculate the magnitude and state the direction of the magnetic flux density at a point P in the plane of the wires if P is (a) midway between R and S, (b) 0.05 m from R and 0.15 m from S. Answers: (a) 1.6 * 10-4 T, (b) zero. 2. The attempt at a solution (a) 0.1 / 2 = 0.05 m. B = μ0 I / 2 π r = 4 π * 10-7 * 10 / 2 π * 0.05 + 4 π * 10-7 * 30 / 2 π * 0.05 = 1.6 * 10-4 T. (b) Because the distance between them is 0.1 m and the given distance (0.05 m and 0.15 m) is greater than the 0.1 m, therefore the magnetic flux density at a point P is zero? Not sure on this part. And how do we determine the direction of the magnetic flux density at P? 30 - 10 = 20 A, so current at S is stronger so we need to take the P line with our current finger pointing downwards and so the field will be on the left side of P into the paper and on the right side it will be out of paper?