几种典型电流体系的磁场 (1) (4) RBx B 4-4兀d 2R (2) Bs× 4R (5) R R (3) B 8R|B=401_0l/ 4R4R,4兀RA d (4) * I o I R1 R2 (5) * o (2) R I R (3) o I I R o (1) R I B 2 0 0 = R I B 4 0 0 = R I B 8 0 0 = 1 0 1 0 2 0 0 4 4 4π R I R I R I B = − − d I BA 4π 0 = x B0 几种典型电流体系的磁场