aR R 解 21+(R Rai +R3)i R R R 1=1,1十1→1,=1 R R RR3+(1-0)R1R R+R 2 +r 若Rn出现负值,则为发出功率的元件。解: S 2 2 3 1 u R i (R R )i S 1 2 u R i 1 S 1 2 1 2 R u i i i i i i i 1 2 3 S 1 3 1 2 in R R R R R (1 )R R i u R 若Rin出现负值,则为发出功率的元件