The voltage and current sources may be connected in different ways either in series or in parallel with the electrical circuit.
When the current sources are connected in parallel with the circuit, then they can be converted to an equivalent current source.
The current sources in series connection are not recommended for the analysis.
Two voltage sourced can be replaced by an equivalent voltage source when they are connected in series but not in parallel.
In Fig 2.35, two sources are considered. Here, source a is higher than than the source b.