Circuit Concepts and Network Simplification Techniques
Today we live in a predominantly electrical world. Electrical technology is a driving force in the changes that are occurring in every engineering discipline. For example, surveying is now done using lasers and electronic range nders. Circuit analysis is the foundation for electrical technology. An indepth knowledge of circuit analysis provides an understanding of such things as cause and e ect, feedback and control and, stability and oscillations. Moreover, the critical importance is the fact that the concepts of electrical circuit can also be applied to economic and social systems. Thus, the applications and rami cations of circuit analysis are immense. In this chapter, we shall introduce some of the basic quantities that will be used throughout the text. An electric circuit or electric network is an interconnection of electrical elements linked together in a closed path so that an electric current may continuously ow. Alternatively, an electric circuit is essentially a pipe-line that facilitates the transfer of charge from one point to another.
Current, voltage, power and energy
The most elementary quantity in the analysis of electric circuits is the electric charge. Our interest in electric charge is centered around its motion results in an energy transfer. Charge is the intrinsic property of matter responsible for electrical phenomena. The quantity of charge q can be expressed in terms of the charge on one electron. which is 1 602 10 19 coulombs. Thus, 1 coulomb is the charge on 6 24 1018 electrons. The current ows through a speci ed area A and is de ned by the electric charge passing through that area per unit time. Thus we de ne q as the charge expressed in coulombs. Charge is the quantity of electricity responsible for electric phenomena.
The time rate of change constitutes an electric current. Mathemetically, this relation is expressed as i t