After completing this chapter, you will be able to: understand concepts and characteristics of the impedance and admittance of AC circuits; define the impedance and admittance of resistor R, inductor L and capacitor C; determine the impedance and admittance of series and parallel AC circuits; apply the voltage divider and current divider rules to AC circuits; apply KCL and KVL to AC circuits understand the concepts of instantaneous power, active power, reactive power, apparent power, power triangle and power factor; and apply the mesh analysis, node voltage analysis, superposition theorem and Thevinin's and Norton's theorems, etc. to analyse AC circuits.