由i=C au c(0)c(0) R (0) c千C (0) S i1(0)=2A R R dc(0)(0) 2(/S) 同理,由l2=L dl2(0 Z2(0 L R l12(0)=(0)-Rl2(0)=0 R dl2(0 0 L
R R i L uC C L i C u Us L R R i C i L (0 ) uc (0 ) uL Us (0 ) (0 ) C C du dt C i + + 由 = C C d C dt u i = (0 ) (0 ) (0 ) 2 S C C L U u A R i i − + − = − − = (0 ) (0 ) 2 ( / ) C C d V u t C S d i + + = = 同理,由 L L di L dt u = (0 ) (0 ) L L d u dt L i + + = (0 ) (0 ) (0 ) 0 L C L u u Ri + − − = − = (0 ) (0 ) 0 L L d u dt L i + + = =
例4图示电路,I=4A,R=R2=292,开关闭合已久, 求开关打开瞬间电阻R1上的电流i,(0)。 解:开关闭合时有 C1 R2 RI (0)=/s=2A, L RI C2 U2(0)=0,Uc1(0)=/sR2=4 开关打开后等效电路如图 R R OV 电阻R,电流 2A RI i1(0+)=1A
1 2 4 , 2 S I A R R = = = 1 (0 ) R i + 例4 图示电路， ，开关闭合已久， 求开关打开瞬间电阻R1上的电流 。 K i R 1 R1 IS C1 C2 L R2 2 1 2 1 (0 ) 0, (0 ) 4 2 U U I R V c C S − − = = = 解：开关闭合时有 1 (0 ) 2 , 2 L S i I A − = = R1 1 (0 ) 1 R i A + = 电阻 电流 i R 1 R1 IS R2 4 V 2 A 0 V 开关打开后等效电路如图