# Electric Circuit Variables

IN THIS CHAPTER

1.1 Introduction

1.2 Electric Circuits and Current

1.3 Systems of Units

1.4 Voltage

1.5 Power and Energy

1.6 Circuit Analysis and Design

1.7 How Can We Check … ?

1.8 DESIGN EXAMPLE—Jet Valve Controller

1.9 Summary

Problems

Design Problems

## 1.1 Introduction

A circuit consists of electrical elements connected together. Engineers use electric circuits to solve problems that are important to modern society. In particular:

1. Electric circuits are used in the generation, transmission, and consumption of electric power and energy.
2. Electric circuits are used in the encoding, decoding, storage, retrieval, transmission, and processing of information.

In this chapter, we will do the following:

• Represent the current and voltage of an electric circuit element, paying particular attention to the reference direction of the current and to the reference direction or polarity of the voltage.
• Calculate the power and energy supplied or received by a circuit element.
• Use the passive convention to determine whether the product of the current and voltage of a circuit element is the power supplied by that element or the power received by the element.
• Use scientific notation to represent electrical quantities with a wide range of magnitudes.

## 1.2 Electric Circuits and Current

The outstanding characteristics of electricity when compared with other power ...

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