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A resistor is a component that resists the flow of current. It’s one of the most basic components used in electronic circuits; in fact, you won’t find a single circuit anywhere in this book that doesn’t have at least one resistor. Figure 3-15 shows three resistors, next to a penny so you can get an idea of how small they are. You’ll learn all about resistors in Book 2, Chapter 2.

FIGURE 3-15: Resistors are one of the most commonly used circuit components.

Resistors come in a variety of resistance values (how much they resist current, measured in units called ohms and designated by the symbol Ω) and power ratings (how much power they can handle without burning up, measured in watts).

All the circuits in this book can use resistors rated for one-half watt. You’ll need a wide variety of resistance values. I recommend you buy at least 10 each of the following 12 resistances:

470 Ω	4.7 kΩ	47 kΩ	470 kΩ
1 kΩ	10 kΩ	100 kΩ	1 MΩ
2.2 kΩ	22 kΩ	33 kΩ	220 kΩ

You can save money by purchasing a package that contains a large assortment of resistors. For example, most suppliers sell a package that contains an assortment of 500 or so resistors — at least 10 of all values listed here, plus a few others, for about $15.