The present work presents the fundamental notions of the theory of electrical circuits, addressing, with priority, students from the fields of "Electrical Engineering", "Electronic Engineering, Telecommunications and Information Technologies", "Computers and information technology", respectively "Multimedia systems engineering". From its content, useful parts can also be selected for students from other fields such as "Industrial Engineering", "Mechatronics and Robotics", etc. The book has a pronounced formative character, the main objective being the presentation of the knowledge of the theory of electric circuits so that it constitutes a real support for courses in the field of electrical engineering. For a better understanding of the theoretical aspects presented, examples of solved problems are also included in each chapter.