R 电压42的叠加 R2 us 2 4 RiR2-is R+R R1+R2 (a) =42+2 R 2 R2一s (b) 4== R+R2 R1 h4=2 RR s R+R (c)+ ' " u u i R R R R u R R R u 2 2 S 1 2 1 2 S 1 2 2 2 = + + + + = S 1 2 2 2 2 0 S u R R R u u i ' + = = = S 1 2 1 2 2 2 0 S i R R R R u u u " + = = = 电压u2的叠加