All right, there are four types of resistors that we're going to speak about fixed potentiometers rheostat, and what I call special application resistors. All right. We're also going to talk about the resistance color code. And the tolerance. All right, the resistor color code determines the ohmic value of the resistor. And the tolerance is another color.

We'll see in some cases, I think it's up, maybe several slides down that will determine the tolerance of the resistor. And you'll see when we get there What I mean by that. We'll also take a closer look at potential nominees and rheostat and adjustable resistors. And we'll we'll end this with a definition and some theory on Special application resistors, which I call thermistors, and barristers. So let's go on to the next slide. And let's start this journey.

Okay, on this slide here, we're looking at some physical resistors. And right here on this side here, we have what I call my fixed resistor types, meaning that the, the resistance value or the ohmic value is fixed one value period, you can adjust it. And if you look at these here, we have a carbon film and a metal film resistor. Okay, that's the material that the resistor is made of. Now, if you look here, you'll see that there's just four bands here. All right.

And if you look at my metal film resistant right here, you'll see That there are five bands. Now, because of the material All right, a metal film resistor has a tighter tolerance and a better temperature coefficient than my carbon film resistor. Carbon film resistors are a little bit more common. But you'll also see a lot of metal film what do I mean by temperature coefficient that as as the environment that the circuit is in, okay is that changes is that gets hotter or colder, the value of the resistance will change, it will change with temperature. So when I say a metal film has a tighter temperature coefficient, the resistor value will stay closer to the what I'll call the published value of the resistor here, the color code And it will stay closer to that where a carbon film it'll very much more. Now is that a problem?

It depends upon the application and the circuit. Okay, over here we have potentiometers, right there are I should say variable resistors, which are potentially ometer is one class or one form of adjustable resistors. If you look here that is a potentially ometer and you turn that clockwise or counterclockwise, and you can turn that shaft 270 degrees. But the point I want to make here is if you look right here, you'll see two sets of terminals. Each set has three connections. Let me play that slide as we go.

So each this shaft attaches to a double gang potentially ometer. So when you turn that each the resistance of each section tracks one of the things that they might want to do with that is a, if you've got a stereo and they want to track two to two channels, you can turn the potentiometer and simultaneously, the resistance on each track will be the same. The same thing here with this one here. All right, ah, over here. We have a multi turn potentiometer where these guys here it's 270 degrees to go from one end or another clockwise to clockwise where this guy here, it may be 510 15 or 20 turns to go from the very minimal minimal resistance to my maximum resistance. And what does that do?

We'll see in the next slide or two coming up that I can get a finer adjustment with a multi turn and potentially ometer than I can with a, a standard potentiometer where I where the revolution or one turn is 270 degrees. Okay, let's look at a another style of variable resistor called a rheostat. And in a few slides up, you'll see the difference between the potentiometer and the rheostat. Okay, but just looking at these here, I'm looking how they physically work. This rheostat is on a slide And you slide it back and forth. And that changes the resistance over here is a like a screwdriver or adjustment.

And you turn this shaft and that also adjust the resistance. And here we have a a shaft where we can turn the shaft and again, change the resistance. So in the next slide there they're coming, I don't remember exactly which order they're in. We're going to look at the differences between a the potentiometer and the rheostat here. All right, so let's, let's go on here to vs and thermistors. And I'm going to explain them versus and thermistors are special application resistors.

And again, we're going to look at them a little deeper at the very end of this presentation. But a varistor right here is a voltage dependent resistor. So it's voltage dependent, where a thermistor right here is temperature and I'll abbreviate temperature right there, I temperature sensitive. So, in a varistor, when I when I have a voltage across this resistor, the resistance will change. And then when I'm using a thermistor depending upon the temperature or the environment that this is in, the resistance will change with a thermistor. We have two types we have a positive temperature coefficient and a negative temperature coefficient.

On a positive temperature coefficient when the temperature increases, so doesn't the resistor on a negative temperature coefficient as temperature rises? The resistance of the thermistor goes down. Or the other thing I want to mention here is the material and the actual physical mounting. Notice this is a radio lead. This is an axial lead, and this is how we can mount them on the circuit board. This one is made out of glass.

All right, so, we'll take a look at these. Later down. I think when we speak about baristas, and thermistors. They're at the very end of this presentation. So let's move on here. Okay, and on this slide, I show you several sizes of fixed value resistors and they range from three watts down to one 16th of a watt.

Now, I'm going to define what a watch Just care, I'm going to just show you the formula, right when you take my circuit analysis course, we'll get into a deeper but power of a component which will determine the wattage rating equals the voltage across the component, in this case, the resistor times the current flow through it. And current is abbreviated by I, so that's current. Alright, so for instance, if I make a calculation here, and I say that the amount of power that's dissipated by the resistor and I'm using specifically resistor here, because that's what we're talking about, is a half walk Then the component or the or the wattage rating of that of the resistor that I should place inside the circuit would be a one watt resistor because what we want to do is we want to overcompensate it. So if I calculate a half a watt, I want to make sure that the component that I put in there or the resistor value that I put in there is double lat or greater and greater is okay too.

But we would like to see at least two times the calculated value. Okay, the next thing I want to speak about is the colorings and on these resistor pictures, you'll see that I have four bands and you can count them. All right, the first digit is closest to the left. You'll notice that all these resistors if you look at them, and I'm going to clear the slide off, but I just wanted to emphasize that is closest to the left, that is the first digit. Okay. Now, on a four band resistor as I'm talking, I'm going to clear the slide off on a four, because we have four and five band resistors.

Alright, so on a four band resistor, you'll notice in this one's very pronounced, that's gold. This is gold, gold, gold, gold, gold there, alright. The last band or the band all the way to the right is the tolerance band. Very hard to get a period with this, okay is the tolerance band and I abbreviated tolerance right there, okay? The tolerance band is the specification on the resistor. In other words that resistor may or may not be may not be exactly the Publish value of the resistor which is determined, in this case by the first three bands right there.

All right. So there's a tolerance plus a minus 5% plus or minus 10% plus or minus 2%. Okay, we'll see how to calculate that in upcoming slides. But that's the tolerance ban. The tolerance ban says okay, I've got this value resistor, the upper limit can be as high as this and the lower limit can be as low as that And we'll see as we go on. All right, so now let's stop here and go on to the next slide.

Okay, on this slide here, we're going to introduce the color code. And what I've done is I've given you a little bit of a poem to try to remember the colors. And the little POM a little saying is right here. big boys race out young girls, but violet generally wins. Now, the first letter of the, this poem represents a color. And what you have to remember is that we go from a dark numb, dark color, which is black, up to a bright color, which is white.

All right, and the first letter of the first word in the poem is the the first Letter of the color for instance, big is black boys is brown. All right, big. Black represents zero boys brown represents one race represents red, and it's the number two, our equals orange. And that's the number three young represents yellow. And that's the number for girls represents green and that's five, but represent represents blue, and that sex. Violet is violet.

And that represents seven and generally equals gray, and that's eight wins equals white, and that's nine. So again, we go from a very dark color, to a very light color. If you can remember that poem. it'll, it'll make life easier. For you, alright, so that's all I'm going to say here, I just take a look at this and try to remember it. And we're going to go on to the next slide.

Okay, let's move on now to part two. And in part two, I show you how to use the resistor color code. We determined some values of resistors. I show you how to do it. And there's a couple of problems for you to do. So let's move on.