180 R A 120 L luF luF 当电路达到新的稳定状态时,电容相当开路得 C 120V OC ×104 u()=U(1-e-)=1201-e)y(t≥0) da ×10t i(1)=C=C=100×120××10e3=04e3A(t>0
当电路达到新的稳定状态时，电容相当开路得 UC () = Uoc =120V 10 e 0.4e A ( 0) 3 1 10 120 d d ( ) ( ) (1 e ) 120(1 e )V ( 0) 4 4 4 1 0 3 1 1 0 3 1 C 6 4 C 1 0 3 1 τ C o c = = = = − = − − − − − − t t u i t C u t U t t t t t
1809 104 lA HIs 1200=val()=120 )V(t≥0) (t)= A(t>0) 根据图(a)所示电路,用KCL方程得到 ×104t (1)=ls-ic(t)=(1-0.4e3)A (t>0) uc(v) IC(A) 0.4 t(s t ( s O τ2τ3τ4τ T2τ3τ4τ
根据图（a）所示电路，用KCL方程得到 ( ) ( ) (1 0.4e )A ( 0) 4 1 0 3 1 1 = S − C = − − i t I i t t t t(s) iC (A) O τ 2τ 3τ 4τ 0.4 t(s) uC(V) 120 O τ 2τ 3τ 4τ 4 4 1 10 3 C 1 10 3 C ( ) 120(1 e )V ( 0) ( ) 0.4e A ( 0) t t u t t i t t − − = − =