Suppose a piece of coaxial cable is made with a solid wire at the cylinder has a common center with the wire and its radius is 1 mm. A2A current flows up the center wire and a 1.5 A current flows down the cylinder.
A) Find the B-field at 4 mm from the center.
B)Find the B-field at 0.5 mm from the center.
B) What current should be in the cylinder to have no B-field outside of cylinder? ​