In the branches of engineering, the electrical part is usually approached as a compulsory subject, since it depends on it that the engineer obtains the basic knowledge, to be able to face in a certain situation or eventuality, some technical problem. Therefore, this material presents the basic principles of electricity, as well as its most important laws, even so, some examples of application are proposed so that the student or the reader can understand some practical applications, although the main purpose is to establish the electrical bases that govern electrical systems.