i is 电压u2的叠加 R RR2 us 2= R+R2 us R+R2 (a) =u2+u2 =460 R2一ls (b) R+R, ”R1 + + 4=42s-0 RR2 R+R2 (c)+ " 2 ' 2 S 1 2 1 2 S 1 2 2 2 u u i R R R R u R R R u       S 1 2 2 0 2 ' 2 S u R R R u u i     S 1 2 1 2 0 2 " 2 S i R R R R u u u     电压u2的叠加