The replacement of a particular energy source by an equivalent source is referred to as source transformation. Common  rules and procedures are listed below with illustration using figure 1.9, 1.10 and 1.11.

1. Voltage sources connected in series are equivalent to the algebraic sum of all sources. 

2. Two voltage sources can not be connected in parallel unless they are equal.  

3. A resistor in parallel with a voltage source may be omitted as the voltage across the branch is the same. Diagram coping problemFig. 1.9 Source transformation rules (i), (ii) and (iii) illustrated

4. Current sources connected in parallel are equivalent to the algebraic sum of all sources. 

5. Two current sources can not be connected in series unless they are equal. 

6. A resistor in series with a current source may be omitted as the current in the branch is the same. Fig. 1.10 Source transformation rules (iv), (v) and (vi) illustrated

7. A voltage source in series with a resistor can be transformed into a current source in parallel with the resistor. The resistance value in the transformed circuit is unchanged and the current source value is calculated using Ohm’s law. 

8. A current source in parallel with a resistor can be transformed into a voltage source in series with the resistor. The resistance value in the transformed circuit is unchanged and the voltage source value is calculated using Ohm’s law.