Draw and explain V-I characteristics of constant voltage and constant current sources.

Ans: V-I Characteristics of Constant Voltage Source: A voltage source that has very low internal resistance (or impedance) as compared to load impedance (or resistance) is called a Constant Voltage Source.

A real voltage source (constant voltage source) has some internal resistance. For example, a flashlight battery has an internal resistance of less than 1 ohm, a car battery has an internal resistance of less than 0.1 ohm and an electronic voltage source may have an internal resistance of less than 0.01 ohm. A real voltage source which is having an internal resistance of 0.01 ohm with load resistance RL is illustrated in below fig (a). When, a load resistance varies from 11.99 ohm to 1.19 ohm, terminal voltage varies from 11.99V to 11.9 V and load current varies from 10A to 1A respectively.

This signifies that  terminal  voltage  remains  constant  and  the  source  behaves  as  a constant voltage source irrespective of load current, as shown in fig.