ABSTRACT
This chapter introduces some basic notions on electric circuits. It begins by explaining what electric circuits are, what they are used for, and what conservation laws they obey. The primary circuit variables of current and voltage are defined with reference to a useful and easy-to-follow, hydraulic analogy. The significance of direction of current and polarity of voltage is emphasized because of the key roles these play in circuit analysis. The relation of current and voltage to power and energy is derived, and active and passive circuit elements are characterized by the way they handle energy. The three passive circuit parameters of resistance, capacitance, and inductance are justified as accounting for three basic attributes of the electromagnetic field, namely, energy dissipation and energy storage in the electric and magnetic fields. The chapter concludes with an examination of the idealizations and approximations made in the circuits approach.
