Forrest Mims Engineer's Notebook

REVIEWING THE BASICS

INTRODUCTION

“Can I use a 0.22 µF capacitor instead of a 0.01 µF unit?”

“Is it okay to substitute a 12,000 ohm resistor for a 10,000 ohm unit?”

This section will tackle these common questions and many others. Master them, and you will be well prepared to tackle the circuits in this book.

RESISTORS

Resistors limit the flow of electrical current. A resistor has a resistance (R) of 1 ohm if a current (I) of 1 ampere flows through it when a potential difference (E) of 1 volt is placed across it. In other words:

$\begin{array}{lllll}\text{R}=\frac{\text{E}}{\text{I}}\hfill & (\text{or})\hfill & \text{I}=\frac{\text{E}}{\text{R}}\hfill & (\text{or})\hfill & \text{E}=\text{IR}\hfill \end{array}$

These handy formulas form Ohm’s law. Memorize them. You will use them often.

Resistors ...