This chapter describes the basic principles of operation of different electromechanical devices, stored energy, counter-EMF and counter-torque/force, types of mechanical loads, hard and soft torque-speed characteristics, AC operation, classifications of electrical machines, duty cycles, IP specifications, material properties of conducting, insulating, thermal and mechanical properties of materials used in electrical machines, inductance from different viewpoints, self, mutual and leakage inductance, A simple method of solving simultaneous differential equations or state variable equation has been described using MATLAB Simulink software.