A=a cos 0 s 0e (7.9a 4r Ao=-4 i Hosin - jk (7.9b) 4丌r A=0 场点尸的磁场强度为 r-sing rsin e V×A Op A raina 将式(7.9)代入上式,得场点P的磁场强度为 2 0 0 sin sin 1 1 sin r r r r r = r A rA r A                =    a a a H A 将式（7.9）代入上式，得 0 j 0 j cos cos (7.9a) 4 sin sin (7.9b) 4 (7.9c) kr r z kr z Il A A e r Il A A e r A           − − = = = − = − = 