a o (a)求开路电压U 69 69 oc IA 12v 202 a a 4g2 + 4Q2 69 6 6 692U3 U 凵IA oc 69 6Q2 T12V b b 202 Uoe=U1=8V,Uoe′=U2+U/3=-4-2=6V,U0c=8-6=2VUoc ' =U1=8V, Uoc ''=U2+U3= -4-2=-6V, Uoc =8-6=2V a b 2 4 6 6 6 1A 12V + –Uoc 2 4 6 6 6 12V b a + Uoc ' – + U1 – 1A 2 4 6 6 6 b a + Uoc '' – + U2 – + U3 – (a) 求开路电压Uoc