Alternating current (ac) refers to systems in which the source voltage varies periodically, particularly sinusoidally. The voltage source of an ac system puts out a voltage that is calculated from the time, the peak voltage, and the angular frequency. Alternating Current is a crucial chapter and concepts involved in 12 Chapter 7 Alternating Current: Introduction, Ac Voltage Applied To A Resistor, Representation Of Ac Current And Voltage By Rotating Vectors — Phasors, Ac Voltage Applied To An Inductor, Ac Voltage Applied To A Capacitor, Ac Voltage Applied To A Series Lcr Circuit, Phasor-diagram solution, Analytical solution, Resonance, Lc Oscillations, Transformers.