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The length of the coaxial transmission line is l with inner and outer conductors of radii a and b respectively. The radial distance from the axis of the coaxial line is r. The directions of the currents in the inner and the outer conductors are opposite to each other. The region of circles with dots between the inner and the outer conductors represents the outward direction of the magnetic field. The region of circles with crosses at center between the inner and the outer conductors represents the inward direction of the magnetic field. A rectangle is sketched around the inward magnetic field that is labeled, S.