2.R<r<R,且d=2mH= .H= →B=44I 20 2π 3.R2 Hdl=2mH =1-I=0 :.H=0→B=0 磁场分布与圆柱导体中的电流满足 右手螺旋定则 2.R1< r <R2 : = L H dl 2rH = I r I H 2 = r I B r 2 0 = r I I R1 R2 L r 3. r>R2 = L H dl 2rH = 0 H = 0 = I − I B = 0 磁场分布与圆柱导体中的电流满足 右手螺旋定则 L