The book is designed for use as a textbook for a first course in circuit analysis or as a supplement to standard texts and can be used by electrical engineering students as well as other engineering and technology students. Emphasis is placed on the basic laws, theorems, and problem-solving techniques which are common to most courses. The book begins with fundamental definitions, circuit elements including dependent sources, circuit laws and theorems, and analysis techniques such as node voltage and mesh current methods. These theorems and methods are initially applied to DC-resistive circuits and then extended to RLC circuits by the use of impedance and complex frequency. Chapter 3, where the concept of complex frequency is introduced, phasor analysis, sinusoidal steady state, power, power factor, and its correction.. Series resonance, quality Factor, Q, power, bandwidth, and selectivity of a series resonant circuit, coupled circuits and transformers are thoroughly covered in Chapter4.The characteristics of three-phase circuits, the analysis of balanced loads and unbalanced Loads, the calculation and measurement of power in three-phase circuits are mainly introduced in the last chapter. It can be used as a primary text or supplementary text. It is also ideal for self-study and provides the technical staffs and university teachers with references.