电机工程学是以电子学、电磁学等物理学分支为基础，涵盖电子学、电子计算机、电力工程、电信、控制工程、信号处理等子领域的一门工程学。十九世纪后半期以来，随着电报、电话、电能在供应与使用方面的商业化，该学科逐渐发展为相对独立的专业领域。

电机工程广义上涵盖该领域的分支，但在有些地方，「电机工程学」（英语：Electrical Engineering）一词的意义有时不包括「电子工程学」（英语：Electronic Engineering）。 这个情况下，「电机工程学」是指涉及到大能量的电力系统（如电能传输、重型电机机械及电动机），而「电子工程」则是指处理小信号的电子系统（如计算机和集成电路）。

Power engineering, also called power systems engineering, is a subfield of energy engineering and electrical engineering that deals with the generation, transmission, distribution and utilization of electric power and the electrical devices connected to such systems including generators, motors and transformers. Although much of the field is concerned with the problems of three-phase AC power – the standard for large-scale power transmission and distribution across the modern world – a significant fraction of the field is concerned with the conversion between AC and DC power and the development of specialized power systems such as those used in aircraft or for electric railway networks. Power Engineering draws the majority of its theoretical base from electrical engineering and while some power engineers could be considered energy engineers, energy engineers often do not have the theoretical electrical engineering background to understand power engineering.