1. The problem statement, all variables and given/known data Three long straight parallell wires that conduct electricity called L1, L2 and L3. The angle at L2 is 90 degrees and the distance between L2 and L1, L3 is 0,50 meters. The current through the wires L1 and L3 is 300 A while the current in L2 is 600 A. Decide the resulting power force (F) per meter at L2. PICTURE: O. the current goes towards you (out from the book for example) Ox the current goes from you (into the book for example) L3 O. ---< | | 0,50m | L1 L2 | O. 0,50m ⊗ ----< |<----------------->| 2. Relevant equations F = I * l * B = [A] * [m] * [T] B = k * (I/a) 3. The attempt at a solution First I thought that I was supposed to use pythagoras theorem to calculate the distance between L1 and L3: l = √(0,50^2+0,50^2) = 0,71 m Using this information I thought I could calculate the power for L1 and L3 and somehow calculate the power for L2 also. I knew I (A) and l (m) but I didn't know B? How am I supposed to be able to calculate B when I don't know what F is? The answer according to my physics book is F = 0,10 N at southeast.