(Solved): 5. A coaxial cable consists of a solid inner conductor of radius a surrounded by a concentric cyli ...

5. A coaxial cable consists of a solid inner conductor of radius $$a$$ surrounded by a concentric cylindrical tube of inner radius $$b$$ and outer radius c. The conductors carry current $$I$$ of equal magnitude flowing in opposite directions. The current density is uniform for each conductor (so $$J$$ does not depend on $$r$$ ). Find an expression for the B-field, in terms of $$I$$, for 4 different distances from the central axis: $$r<a;a<r<b;b<r<c$$; and $$r>c$$