Before turning to time-dependent electromagnetics, there exists a transitional subject between time-dependent and time-independent electromagnetics, called quasi statics. Quasi statics includes quasi electrostatics and quasi magnetostatics, the later which includes Faraday law. Due to its various applications in electric machines, we only discuss quasi magnetostatics in Sect. 6.1. We then discuss time-dependent electromagnetics in Sect. 6.2 covering the Poynting theorem, which describes the conservation of energy in electromagnetics.