[问答题]
(a) Use Ampère’s law toz fbxt5in9e(- show that the magnetic field between the cond;yue7egzn: ;;vm9 hmaq zc;5x b0w+oxuctors of a coaxial cable (Fig. Below) i ;zqug;0a7:;y xhcnvx m e+ wemz9b;5os $B=\mu_0I/2\pi r$ 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.
