第十五章磁场的源 R2+2=R2cc2Bpa单 1=RcgB4≤ r P dl=-Rcsc dB 区88888888区888888 B=14B=~n/2 sin Bap BI nl(cos B2-cos Bu)第十五章 磁场的源  2 2 2 2 R +l = R csc A1 A2 R P 1  2 l dl r  dl R d 2 = − csc l = Rctg    = L B dB  = − 2 1 sin 2 0      nI d (cos cos ) 2 2 1 0    = nI −