(3)通电直螺线管轴线上: 2(cosB2-COSP1) B x无限长通电直线管内: 8888888888888888 B=Honl (4)通电螺绕环内: ⊙ee B≈40 tTR 88 通电细螺绕环内:B=μonl ∞888 通电细螺绕环外:B=0 ⊙68 (cos cos ) 2 2 1 0 − = nI B 无限长通电直线管内: B nI = 0 1 2 x p B (3)通电直螺线管轴线上: (4)通电螺绕环内: r NI B = 2 0 通电细螺绕环内: B nI = 0 通电细螺绕环外: B = 0 B