ASSIGNMENT 2
Part 1
First Order Circuit (RC and RL)
1. A voltage of V appears across a parallel combination of a 100-mF capacitor and a 12 ohms
resistor. Calculate the power absorbed by the parallel combination.
2. An inductor has a linear change in current from 50 mA to 100 mA in 2 ms and induces a
voltage of 160 mV. Calculate the value of the inductor.
3. The switch in Fig. 4 has been in position A for a long time. At t = 0, the switch moves from
position A to B. The switch is a make-before-break type so that there is no interruption in
the inductor current. Find:
(a) i(t) for t > 0,
(b) v just after the switch has been moved to position B,
(c) v(t) long after the switch is in position B.
40V
Figure 4
20 A
4. The inductors in Fig. 5 are initially charged and are connected to the black box at t = 0. If
i1(0) = 4 A, i2(0) = -2 A, and v(t) = 50e-200t mV, t  0$, find:
(a). the energy initially stored in each inductor,
(b). the total energy delivered to the black box from t = 0 to t = ,
(c). i1(t) and i2(t), t  0,
(d). i(t), t  0.
Figure 5
5. In the circuit shown in Fig. 6
v(t)=56e-200t V, t>0
i(t)=8e-200t mA, t >0
(a) Find the values of R and C.
(b) Calculate the time constant 
(c) Determine the time required for the voltage to decay half its initial at t=0.
i
+
R
v
–
Figure 6
C
6. Find the time constant for the RC circuit in Fig. 7
Figure 7
7. Determine the time constant for the circuit in Fig. 8
10 k
20 k
100 pF
40 k
30 k
Figure 8
8. The switch in Fig. 9 moves instantaneously from A to B at t=0. Find v for t>0.
5 k
A
+
_
B
10 F
+
40 V
v
2 k
Figure 9
9. The switch in Fig. 10 has been closed for a long time, and it opens at t = 0. Find v(t) for t  0.
v(t)
Figure 10
10. Assuming that the switch in Fig. 11 has been in position A for a long time and is moved to
position B at t=0, find vo(t) for t  0.
20 k
t=0
B
+
A
_
+
2 mF
12 V
vo
40 k
20 k– Figure 11
11. The switch in Fig. 12 opens at t=0. Find vo for t > 0.
2 k
t=0
+
+
_
6V
vo
–
4 k
Figure 12
50 μF
12. For the circuit in Fig. 13, find io for t >0.
3
t=0
4H
io
+
_
4
8
24 V
Figure 13
13. Calculate the time constant of the circuit in Fig. 14
20 k
10 k
5 mH
40 k
Figure 14.
30 k
Part 1
Assignment for RLC
1.
2.
3.
Formulate the differential equation for the series RLC circuit
Formulate the differential equation for the parallel RLC circuit
If R = 20 ohms, L = 0.6 H, what value of C that will make an RLC series circuit :
a. Overdamped
b. Critically damped
c. Underdamped
4.
For series RLC circuit with R = 2  and L = 1 H, analyse the resonant frequency, o
for each C (where C = 1 F, C = 0.5 F and C = 2 F).
5.
The switch in the circuit of Figure 1 has been closed for a long time but is opened at
t = 0.
Figure 1
a. Find values of  and o.
b. Define its characteristic equation.
c. Determine i(t) for t>0.
6.
For the circuit shown in Figure 2, find
Figure 2
7.
For RLC circuit in Figure 3 below :
Figure 3
a. Find values of  and o.
b. Define its characteristic equation.
c. Determine i(x) and VR for t>0.