The book chapter presents an introduction to electric circuits by considering: electric circuits and schematic diagrams; electric current; electric voltage; resistance and Ohm's law and the reference direction of voltage and current.

The book chapter studies series-parallel resistive circuits by considering: series resistive circuits and voltage divider rule; parallel resistive circuits and current divider rule; specific series-parallel resistive circuits; Wye (Y) and delta (Δ) configurations and their equivalent conversions.

The scientists working in the field of the electrical engineering have developed more simplified theorems to analyze these kinds of complex circuits (the complicated circuit is also called the network). This chapter presents several theorems useful for analyzing such complex circuits or networks. These theorems include the superposition theorem, Thevenin's theorem, Norton's theorem, Millman's theorem, and the substitution theorem. In electric network analysis, the fundamental rules are still Ohm's law and Kirchhoff's laws.

There are three basic elements in an electric circuit, the resistor R, capacitor C, and inductor L. The circuits in this chapter will combine the resistor(s) R with an energy storage element capacitor C or an inductor L to form an RL (resistor-inductor) or RC (resistor-capacitor) circuit. These circuits exhibit the important behaviors that are fundamental to much of analogue electronics, and they are used very often in electric and electronic circuits. Analysis RL or RC circuits still use KCL and KVL. The main difference between RL or RC circuits and pure resistor circuits is that the pure resistor circuits can be analyzed by algebraic methods. The relationship of voltages and currents in the capacitor and inductor circuits is expressed by the derivative and differential equations (the equations with the derivative). RL or RC circuits that are described by the first-order differential equations, or the circuits that include resistor(s), and only one single energy storage element (inductor or capacitor), are called the first-order circuits.

The DC (direct current) power supply provides a constant voltage and current, hence all resulting voltages and currents in DC circuit are constant and do not change with time. The polarity of DC voltage and direction of DC current do not change, only their magnitude changes. Before the nineteenth century, the DC power supply was the main form of electrical energy to provide electricity. An alternating voltage is called AC (alternating current) voltage and alternating current is called AC current. The AC voltage alternates its polarity and the AC current alternates its direction periodically. Since the AC power supply provides an alternating voltage and current, the resulting currents and voltages in AC circuit also periodically switch their polarities and directions. In the nineteenth century, DC and AC have had constant competition, AC gradually showed its advantages and rapidly developed in the latter of the nineteenth century, and is still commonly used in current industries, businesses, and homes throughout the world. This is because the AC power can be more cost-effective for long-distance transmission from power plants to industrial, commercial, or residential areas. This is why power transmission for electricity today is nearly all AC. It is also easy to convert from AC to DC, allowing for a wide range of applications.

The chapter begins by discussing series resonance, and goes on to consider bandwidth and selectivity, and parallel resonance. The chapter concludes by presenting a practical parallel resonant circuit.

The chapter begins with a discussion of dependent sources, including an introduction, the different types, equivalent conversion, and circuits with dependent sources. It goes on to discuss their analysis using Kirchoff's Voltage Law, Kirchoff's Current Law, node voltage, mesh current, superposition theorem, and Thevenin's theorem.