例2 求uc、ic的冲激响应: i(t),u()sC= δ 00− =
+
+ I (s) Ic(s)
i ic s
s U (s)
u R c
c 1/sC
R C −
− I s (s) = 1
1
R ×
R
U (s) = sC I (s) =
C 1 S
R + RC(s + 1/ RC)
sC
RsC 1
I (s) = U (s)sC = = 1−
C C RsC + 1 RsC + 1
1 −t/RC 1
u(t)= e ε −tRC/
c itc =−δ ()e ε () t
C RC 1
ic
uc (V)
1 δ (t)
C t
0 t − 1
RC
例3
R1 L L
1 2 t = 0时打开开关k ,
i 求电流 i1, i2。
+ 2Ω 1 i2
10V 3Ω i(05− )= A
k R2 1
Us i(00 )=
- 2 −
2
1
I (s)
1 10
+ 10 +
2 3 I (s) = s =
1 5 + (5 + )s
25 +
10/s =
(s + )s
2
− 5 = +
= 2175+>e t 0 s s +
i 显然:
5
ii11(0+− )≠ (0 )
ii(0+− )≠ (0 )
2 22
0 t
3
I 1(s) 1
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