2.2换路定则（开闭定则） A电容的电荷和电压 十 9c()=i(5)d5 k.)=3 uc 宁C-55+ga5「5+2〔ea dq dt =9c(0.)+i(5)d5 F40)+255 4c=Cuc qc(0.)=9c0.)+0i(5)d5 当t=0时， 0,)=40)+25a 当)为有限值时， 05d5=0 9c(0+)=9c(0) Lc(0+)=uc(0)2.2 换路定则 (开闭定则) 当t = 0+时, ()d 1 (0 ) (0 ) 0 0       i C u u C C C i uC + –         (0 ) ( )d ( )d ( )d ( ) ( )d 0 0 0                t C t t C q i i i q t i         ( )d 1 (0 ) ( )d 1 ( )d 1 ( )d 1 ( ) 0 0 0                t C t t C i C u i C i C i C u t (0 ) (0 ) ()d 0 0   q   q   i C C ( )d 0 0 0     i   qC (0+ ) = qC (0 ) uC (0+ ) = uC (0 ) 当i(t)为有限值时, t q i d d  qC =CuC A 电容的电荷和电压