...||==|| .||.......|| ||... 0...|| ..||......|| ...||==|| This is a really bad picture, but it should kind of give the idea. How do I deal with a system where a current is running in a cylinder surrounded by a cylindrical shell? I know this sounds like a homework question, and it is related to a few of them, but it's the whole concept of the system I don't really understand. Basically I need to know how to find the magnetic field inside the cylinder, between the cylinder and the shell, in the shell, and outside the shell. Is it basically just a sum of the two independent fields? Also do the fields cancel outside of the shell if the currents are opposite?