An voltage source provides constant voltage to external circuit, whereas a current source provides constant current to external circuit. A practical voltage source always contains some series resistance.
![](https://electricalandelectronicsengineering.com/wp-content/uploads/2019/06/voltage-source-internal-construction-300x189.jpg)
Just like voltage source, a current source also has some internal resistance, but unlike voltage source this resistance is shunt.
![](https://electricalandelectronicsengineering.com/wp-content/uploads/2019/06/internal-construction-of-current-source-300x216.jpg)
If we want to convert one of above mentioned source to other one we can easily do so by using the following formula:
Source conversion formulas:
- To convert current source to voltage source: E = I.Rsrc
- To convert voltage source to current source: I = E/Rsrc
An Example
Find the equivalent current source for circuit given below. Once done find the current provided to load and prove that both sources deliver equal current to load.
![](https://electricalandelectronicsengineering.com/wp-content/uploads/2019/06/r-and-voltage-source-circuit-1-300x210.jpg)
Using formula I = E/R (src) = 5 V / 20 ohms = 0.25 Amps
![](https://electricalandelectronicsengineering.com/wp-content/uploads/2019/06/r-and-current-source92-300x170.jpg)
Let’s find the current provided by both sources to load.
In case of voltage source
Using Ohm’s law
I (load) = V/R = 5 V / (20 Ω + 10 kΩ) = 0.4 mA … (1)
In case of current source
Using current divider rule
I (load) = (Req/Rload) * I(s)
I (load) = (19.96/10kohm) * 0.25 A =0.4 mA … (2)
From two