AEE1141 / MEC1131- Fundamentals of Electronics and Circuits
Dr Hong Fan, University of Glasgow, 2022
Tutorial – Topic 7: Filters
[Source-Free RC and RL Circuits]
7.1 The switch in Figure 7.1 has been closed for a long time, and it opens at t = 0. Find v(t) for t ≥ 0.
When switch is closed , t < 0
Figure 7.1 2
V10) = 1 24 )
/0 + 2
= LIV
when switch is opened ,
t ≥0
RC Circuit is source - free
¥
i. T = RC
= I2 ✗ 103 ) ( 40×10-6 )
↳ ◦µ,=
= 0.085
Vlt ) = V10) e-
¥
= 8e- 12 -5T U
#
7.2 For the circuit in Figure 7.2, find io for t > 0.
t< 0 , switch is closed
Reg = (81/4) + 3
814 )
= + 3
8+4
= ¥ r
Vs
IT =
Req
24
=
17 Figure 7.2
3
≈ 4 235
ni.io
.
4
( O) = (4-235)
4+8
≈ 1 . 412 A
t≥ 0 ,
switch is opened ,
RL circuit is source free -
L
:-c =
R
of
5É
"
=
4+8
I
Sio
=
3
=
io 101 e- ¥ 1
3£
= 1. 412 e- A
#
Dr Hong Fan, University of Glasgow, 2022
Tutorial – Topic 7: Filters
[Source-Free RC and RL Circuits]
7.1 The switch in Figure 7.1 has been closed for a long time, and it opens at t = 0. Find v(t) for t ≥ 0.
When switch is closed , t < 0
Figure 7.1 2
V10) = 1 24 )
/0 + 2
= LIV
when switch is opened ,
t ≥0
RC Circuit is source - free
¥
i. T = RC
= I2 ✗ 103 ) ( 40×10-6 )
↳ ◦µ,=
= 0.085
Vlt ) = V10) e-
¥
= 8e- 12 -5T U
#
7.2 For the circuit in Figure 7.2, find io for t > 0.
t< 0 , switch is closed
Reg = (81/4) + 3
814 )
= + 3
8+4
= ¥ r
Vs
IT =
Req
24
=
17 Figure 7.2
3
≈ 4 235
ni.io
.
4
( O) = (4-235)
4+8
≈ 1 . 412 A
t≥ 0 ,
switch is opened ,
RL circuit is source free -
L
:-c =
R
of
5É
"
=
4+8
I
Sio
=
3
=
io 101 e- ¥ 1
3£
= 1. 412 e- A
#
