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226 ⏐⏐⏐ SERIES-PARALLEL NETWORKS
10 �
E 120 V 20 �
30 �
FIG. 7.34
Voltage divider supply.
a
120 V
b
100 V
c
60 V
0 V
S
S P P
material. For Mathcad, however, we must be sure that the defining
sequence for each new variable flows from left to right, as shown in Fig.
7.33, until R 10 is defined. We are then ready to write the equation for the
total resistance and display the result. All the remaining parameters are
then defined and displayed as shown. The results are an exact match
with the longhand solution.
The wonderful thing about Mathcad is that this sequence can be put
in memory and called for as the need arises for different networks. Simply
redefine the parameters of the network, and all the new values for
the important parameters of the network will be displayed immediately.
FIG. 7.33
Using Mathcad to analyze the ladder network of Fig. 7.27.
7.4 VOLTAGE DIVIDER SUPPLY
(UNLOADED AND LOADED)
The term loaded appearing in the title of this section refers to the application
of an element, network, or system to a supply that will draw current
from the supply. As pointed out in Section 5.8, the application of a
load can affect the terminal voltage of the supply.
Through a voltage divider network such as the one in Fig. 7.34, a
number of terminal voltages can be made available from a single supply.
The voltage levels shown (with respect to ground) are determined by a
direct application of the voltage divider rule. Figure 7.34 reflects a noload
situation due to the absence of any current-drawing elements connected
between terminals a, b, or c and ground.
The larger the resistance level of the applied loads compared to the
resistance level of the voltage divider network, the closer the resulting
terminal voltage to the no-load levels. In other words, the lower the
current demand from a supply, the closer the terminal characteristics
are to the no-load levels.