#9 - Resistors Intro

What’s a Resistor

So far we’ve used a water system analogy to explain voltage and current. Remembering that analogy we said voltage was like a water pump that can provide pressure to the system and current is how fast the water is actually moving through our pipes (wire). Resistance would be anything introduced in our system to slow the flow of current. Think of pinching one of our pipes or inserting a flow regulator. Those things resist the flow of water. Similarly, resistors resist the flow of current.

Color Bands

Resistors come in different flavors and can have 4, 5 or even 6 color bands on them to indicate their resistance value. We’ll be using exclusively 4 band resistors in the projects we’ll be doing on the site. All you need to remember for a 4 band resistor is that each color corresponds to a number. The chart below illustrates that (big thanks to Michael). Feel free to download it or print it out to have it handy. Once you know the number associated with each color you just remember that the first two bands are the left-most digits of the resistance and the 3rd band is the number of zeroes you put after the first two digits. The final band is the tolerance and tells you withing what percentage the actual resistance should measure. That’s it.

How to Read Resistors Chart

Power Dissipation

In the video I briefly mentioned the power rating of resistors. For now all we will need are 1/4 watt resistors as we won’t be dealing with significant amounts of power but I wanted you to be aware of it and there are links under the Resource section on this page where you can learn more. We established the fact that resistors resist the flow of current. The simplest way to think about it is that by slowing down the current it creates a friction of sorts which in turn generates heat. If the power rating of your resistor isn’t sufficient for the amount of heat the current will generate then you can actual destroy your resistor.


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