1. The problem statement, all variables and given/known data The magnetic field inside a cylindrical solenoid of area 4 cm^2 is 0.15 T along the axis of the solenoid. What is the magnetic flux through a disk of radius 3 cm placed perpendicular to the solenoid axis? 2. Relevant equations [tex]\phi = \zeta B * dA [/tex] 3. The attempt at a solution Well the area is 4 cm^2 and B is 0.15, so 6E-5 Wb is the answer, but I'm a little confused here. I thought flux for a closed surface was always 0 (gauss' law for magnetism)? What's going on here?