In contrast to a practical voltage source, an imaginary deal source provide constant voltage regardless of load current because of no internal resistance. While ideal current source provides a constant current regardless of load current.
Star Delta Transformations and Delta Star Transformations allow us to convert resistances or impedances connected together at three different nodes from one type of connection to another and vice versa.
Maximum Power Transfer Theorem state that maximum power will transfer from source to load if and only if the load resistance is equal to source internal resistance. The theorem is purely about the transfer of power not efficiency.
Introductory circuit analysis is the book for the students with circuit analysis tools starting from basic with DC circuit then apply all these tools to AC circuit. Afterward, it describes Decibels and Bode plot and a touch to system analysis.
According to Thevenin Theorem, a complex circuit is reduced to two resistor network, Thevenin Resistor, and Load resistor and a Thevenin Voltage source to avoid redundant computation to analyze a frequent changing resistor.