Solution 2.9.6.3
R
i(t)
Switch closes at t = 0
e(t) C
v
C
(0)
Figure 1: Series RC circuit
For the circuit of Figure 1, weassume v
c
(0) = 0. Kircho's law yields
e(t)=
1
C
Z
t
0
i()d + v
c
(0)+ i(t)R:
Applying the Laplace transform weobtain
E(s) =
1
Cs
I(s)+
v
c
(0)
s
+ I(s)R
This can be rearranged as
I(s)=
1
R
sE(s);v
c
(0)
s +1=RC
For
e(t)=V;;
E(s)=V=s:
Then for v
c
(0)=0,wehave
I(s)=
1
R
V
s +1=RC
;;
and
i(t)=(1=R)e
;t=RC
1(t):
1