i is 电流i,的叠加 us i=R+R2 - + R1+R2 (a) R =,+ =wR +R2 S (b) + + -R2-is 式=FR+R (c)' " i i i R R R u R R i 1 1 S 1 2 2 S 1 2 1 1        + S 1 2 2 1 1 S 0 i R R R i i u "      1 S 1 2 1 1 S 0 u R R i i i '     电流i1的叠加