Robot Building for Beginners, Third Edition

APPENDIX A

■ Appendix A: Appendix A

This appendix contains notes and other items not covered in the main portion of the book. It begins with

proper credit to Ohm’s law, which describes the interdependent relationship between voltage, current, and

resistance. Then, I come clean about some of the mistakes I made during development, so that you can

avoid them yourself. Finally, the appendix concludes with an explanation and listing of the various labels for

positive and negative power.

Magical Ohm’s Law

Most of the electrical formulas in the book are derived from Ohm’s law. Therefore, it would be remiss not to

directly describe the most valuable set of math equations for electronics.

Ohm’s law describes the relationship between voltage, current, and resistance. If you have any two of

those parts, you can instantly calculate the third. You can divide voltage by either of the other two parts, or

multiply current and resistance together (see Figure A-1). Let that triangle burn into your head and you’ll

never forget which part needs to be divided and which parts multiplied.

Figure A-1. Ohm’s law expressed as a triangle, where V is volts, A is amps, and W is ohms

Here are the formulas expressed in a standard way:

current in amps = voltage in volts / resistance in ohms

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