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Guide to the National Electrical Code by Thomas L. Harman

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Chapter 13Review of Electrical Theory

This chapter presents a brief review of electrical theory consistent with the level presented in the Guide and in the various examinations. The areas of direct-current theory, conductors, alternating-current theory, and equipment in alternating-current circuits are discussed. Important formulas for problem solving in these areas are listed in Appendix A for convenient reference. The test in this chapter requires the application of these formulas to solve problems typical of many electrician’s examinations.

13–1 Direct-Current Theory

The calculation of current and voltage in a direct-current circuit containing only resistive elements is determined by Ohm’s law. This basic law states that the voltage across ...

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