So i was doing a question from Irodov(Q 3.238) & got stuck for hours (as expected) The question goes - A thin conducting strip of width h is tightly wound in the shape of a very long coil with cross-section radius R to make a single layer straight solenoid. A direct current I flows through the strip. Find the magnetic induction inside and outside the solenoid as a function of the distance r from its axis. After looking at the solution, it said that current will flow obliquely in the strip i.e. current density will have two perpendicular components. I don't understand this. Why is it necessary that current will flow obliquely & not along the length? And if this is the case, then current should flow obliquely in all 2-D objects. Also, I would like to know how do we determine this kind of current distribution(like in 3-D & other 2-D objects).