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Circuit Concepts

1.1 Electrical Quantities

1.2 Lumped-Circuit Elements

1.3 Kirchhoff’s Laws

1.4 Meters and Measurements

1.5 Analogy between Electrical and Other Nonelectric Physical Systems

1.6 Learning Objectives

1.7 Practical Application: A Case Study—Resistance Strain Gauge

Problems

Electric circuits, which are collections ofcircuit elementsconnected together, are the most

fundamental structures of electrical engineering. A circuit is an interconnection of simple elec-

trical devices that have at least one closed path in which current may flow. However, we may

have to clarify to some of our readers what is meant by “current” and “electrical device,” a

task that we shall undertake shortly. Circuits are important in electrical engineering because

they process electrical signals, which carry energy and information; a signal can be any time-

varying electrical quantity. Engineering circuit analysis is a mathematical study of some useful

interconnection of simple electrical devices. An electric circuit, as discussed in this book, is

an idealized mathematicalmodelof some physical circuit or phenomenon. The ideal circuit

elements are the resistor, the inductor, the capacitor, and the voltage and current sources. The

ideal circuit model helps us topredict, mathematically, the approximate behavior of the actual

event. The models also provide insights into how todesigna physical electric circuit to perform a

desired task. Electrical engineering is concerned with theanalysisanddesignof electric circuits,

systems, and devices. In Chapter 1 we shall deal with the fundamental concepts that underlie

all circuits.

Electrical quantities will be introduced first. Then the reader is directed to the lumped-

circuit elements. Then Ohm’s law and Kirchhoff’s laws are presented. These laws are sufficient

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