# Systm #18: Obey the Laws (of Power)

Posted in Podcasts, Science on November 07, 2008

Calculating resistance and power isn't hard... and, as David explains, knowing Ohm's Law and the Power Triangle can be darn useful when you're designing a project, sorting out power supply issues, or want to keep from burning your car down.

We get a little Engineering 101 in Episode 18. With good reason: David's had a lot of questions about the formulas he uses when he's putting together a project.

So we're going over Ohm's Law, and Power Triangle. They're darn useful when you're designing a circuit and sorting out power supply issues. Or, say, if want to keep from burning your car down when you drop in that 1000W amplifier that draws 83 amps. (It's all about using the right gauge of wire for the amperage you draw. )

David also takes the time to explain the difference between series and parallel circuits, which is most usefull when you're trying to bridge a bunch of AA batteries into a combination of volts and amps that'll power your project.

Now, given the number of engineers (and various other forms o' technical folk) in the audience, we expect a rather spirited debate in the forums on the subject.

We also expect much heckling of Patrick for the fear in his eyes whenever it's time to do math (it's hard, he'd rather go shoppiWe also expect much heckling of Patrick for the fear in his eyes whenever it's time to do math (it's hard, he'd rather go shoppiWe also expect much heckling of Patrick for the fear in his eyes whenever it's time to do math (it's hard, he'd rather go shoppiWe also expect much heckling of Patrick for the fear in his eyes whenever it's tmps from Watts and Volts. (So our 1000W amp running on a 12V system would draw 83A... who knew algebra would be so useful!)

The power law is sometimes called Watt's Law (Wikipedia says 'The name Watt's Law is used only informally, and is not found in authoritative sources such as technical dictionaries [2][3]. This is because the law combines Joule's Law with Ohm's Law, and has nothing to do with the engineer James Watt.')

Watts, by the way, are part of the International System of Units the modern form of the Metric Systm. Er... System.

Tags: Hardware, Systm, Revision3, Energy