272
Practical MATLAB
® Applications for Engineers
The script fi le vol_RL is executed and the results are as follows:
>> vol _ RL
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The peak value (in volts) and the phase (in degrees) of v(t) are=
Vmax =
250
Phasedegree =
36.8699
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The preceding result means that v(t) = 250 cos(100t + 36.8699°) V.
Example 3.5
Evaluate the current i(t) for the circuit shown in Figure 3.53 by hand, and by using
MATLAB.
ANALYTICAL Solution
V = 200 ∠0°, Z = 20 –
j
_____________
125 ∗ 10
–6
∗ 500
= 20 – j16
then
I
V
Z
j
j
ϭ ϭ
Ϫ
ϭ Ϫ
ϭ
Њ
200
20
16
50
5
4
7 8 38 6
.
.
∠
A
Therefore, i(t) = 7.8 cos(500t + 38.6°) A.
MATLAB Solution
>> W = 500;
>> V = 200;
>> R = 20;
>> C = 125e-6
FIGURE 3.53
Network of Example 3.5.
C = 125 µ F
i (t )
v (t ) = 200 cos(500 t ) V
R = 20 Ω
CRC_47760_CH003.indd 272
CRC_47760_CH003.indd 272
7/23/2008 1:27:44 PM
7/23/2008 1:27:44 PM