Chapter 31: Alternating Current

Students learn how AC quantities vary with angular frequency and discover the significance of root mean square values in practical measurements and power calculations. The chapter systematically examines circuit elements in AC systems, comparing resistive behavior where voltage and current remain in phase with reactive components that introduce phase shifts - inductors causing voltage to lead current by ninety degrees and capacitors causing voltage to lag behind current. Through impedance analysis of series LRC circuits, students master vector addition of voltages and understand how the relationship between inductive and capacitive reactance determines overall circuit behavior and phase relationships. The treatment of AC power emphasizes the distinction between resistive power dissipation and reactive energy storage, introducing the power factor as a measure of energy transfer efficiency and explaining practical methods for power factor correction in industrial applications. Resonance phenomena receive detailed attention, showing how circuits achieve maximum current flow and unity power factor when inductive and capacitive reactances balance at the resonant frequency. The chapter concludes with transformer theory, demonstrating how mutual inductance enables voltage transformation through turns ratios while conserving power in ideal conditions. Students examine impedance matching applications and learn about practical transformer limitations including resistive losses, hysteresis effects, and eddy current formation, while understanding how laminated core construction minimizes these inefficiencies in real-world power distribution systems.