A very long coaxial cable consists of a solid cylindrical inner conductor of radius 3.6 mm, surrounded by an outer cylindrical conductor with inner radius 7 mm, and outer radius 9.7 mm. The region between the two conductors is filled with a waxlike insulating material to keep the conductors from touching each other. The inner conductor carries a current 3.1 A, into the page, while the outer conductor carries a current 2.4 A, out of the page.
a) Use Ampère's law to derive an expression for the magnetic field as a function of r (the distance from the central axis) at points inside the outer conductor (R_2i
b) Use Ampère's law to derive an expression for the magnetic field as a function of r (the distance from the central axis) at points outside the outer conductor (r > R_2o). Use this expression to find the magnetic field at 13.05 mm.