Anyone concerned with aircraft maintenance is aware of the increasing use of electricity in modern systems and recognizes the importance to the mechanic of a thorough understanding of electrical principles. While the use of electricity today is so common as to be taken for granted, its widespread use in aircraft electrical systems emphasizes the importance of a sound electrical background for the airframe and powerplant technician.

In the study of physics, the electron theory of the structure of matter was introduced to explain the fundamental nature of matter. A more detailed examination of this theory is necessary to explain the behavior of the electron as it applies to the study of basic electricity.