1. The problem statement, all variables and given/known data A simple loop of 5 cm radius encompasses the middle turns of a long coil. The coil has 2500-turns, is of length 1 m and radius 1 cm, and carries a current of 10 Amps. What is the magnetic flux through the single loop? 2. Relevant equations B=μIN/L with L=1: B=μIN flux=∫B.dA 3. The attempt at a solution flux= μIN*A(loop)= 4π*10^-7*10*π*(5*10^-2)^2 This is not right apparently the actual answer uses the area of the solenoid. Why is that? FLux is the B field dotted with perpendicular area, so why is it the solenoid area? That means that flux is independent of the loop's size!