[问答题]
(a) Use Ampère’s law to show that tw/*o+kmie2d g/q0c8xa(+spexs 7 p uyhe-knkqtcb,pv hce 7.o5,( .vau magnetic field between the conductors of a coan,u k-v epvch k(qtc..7o5 b,axial cable (Fig. Below) is $B=\mu_0I/2\pi r$ if r is greater than the radius of the inner wire and less than the radius of the outer cylindrical braid.
(b) Show that B = 0 outside the coaxial cable.
