This can also be subdivided into ideal and non-ideal sources.
The Ideal Voltage Source An ideal voltage source, shown in Figure 2.9(a), has a terminal voltage which is independent of the variations in load. In other words, for an ideal voltage source, the supply current alters with changes in load but the terminal voltage, VL always remains constant. This characteristic is depicted in Figure 2.9(b).
(a) An ideal voltage source. (b) V − I characteristics of an ideal voltage
source.
Figure 2.9: Schematic and characteristics of an ideal voltage source
Non-Ideal or Practical Voltage Source For a practical source, the terminal voltage falls off with an increase in load current. This can be shown graphically in Figure 2.10(a).
This behaviour can be modelled by assigning an internal resistance, Rs, in series with the source as shown in Figure 2.10(b).
(a) V −I characteristics of a practical voltage source