关联方向时,u= –Ldi/dt 。РР例1:图示电路,已知iL(0)=0, uL波形如图,求 iL(t)表达式及波形。Р-РL=1HР+РuLРiLРuL(t) (V)Р0РaР2aРtРaР1Р(分段)为什么?Р解:РРР1РaР2aРtР0РiL(t)Р1Р2РР§6-3 电容、电感的串、并联Р当电容、电感元件为串联或并联组合时,可用一个等效电容或等效电感来替代。Р一、电容的串并联Рu= u1+u2+…+u nР…Рu1= u1(0)+ 1/C1∫ idξРu2= u2(0)+ 1/C2∫ idξРun= un(0)+ 1/Cn∫ idξРu= u1(0)+ u2(0)+…+ u n (0)? +( 1/C1+ 1/C2+…+ 1/C n )∫ id ξР1、串联Рu1Рu2Рu nРC1РC2РC nР+Р+Р+Р+Р-Р-Р-Р-РuРiР由元件VCRР由KVLРРu1Рu2Рu nРC1РC2РC nР+Р+Р+Р+Р-Р-Р-Р-РuРiРiРCРuР+Р+Р-Р-РuР1/C =1/C1+ 1/C2+…+ 1/C nР2、并联Рi1Р+Р-РuРiРC1РC2РCnРi2РinРi1=C1du/dtРi2=C2du/dtРin=Cndu/dtР由元件VCRРРi= i1 + i2 +….+ in ? =C1du/dt+C2du/dt+…+C2du/dt? =Cdu/dtР由KCLРi1Р+Р-РuРiРC1РC2РCnРi2РinРC=C1+C2+…+CnРiРCРuР+Р+Р-Р-РuРР二、电感的串并联Р1、串联Р+Р-РuРLРu = u1+u2+…+u n? =L1di/dt+ L2di/dt+…+ Lndi/dt? =(L1+L2+…+Ln)di/dt? =Ldi/dtРL = L1+L2+…+LnР+Р-РuРL1РL2РLn