Welcome to How resistors use Part Four. Let's continue. Okay, we're going to be talking about potentiometers here. And right here, here, I'm showing you on the top, top portion here, we're showing you up. Dual gang potentiometers concentric, tenshi ometer a multiband. Well, I'm sorry, multi turn potentiometer ometer.

And right here is the schematic representation of a potential ometer. And here's how we spell it. All right, let me let me change my pointer here. And what are Want to say here before we go on, we're going to explain this right here. But let's talk about this, this and this. And I want to go to the next slide here because I've blown that up.

And if you look, you will see two sets of terminals here. And actually, if you look, you'll see them right here. Also, there are two sets of terminals. And basically, what they do when they say gang is we have two sets, independent sets here, and the center arm. Or we could call it the wiper. He wrote, they rotate at the same point.

All right, so let's go back to the other slide. And let's let's go Go back on that I, what I what I'd like to do here before I go back, let me erase this, because we're probably going to need this the slide. Alright, so now let's let's get rid of the markings on here also. Okay, so now let's just see how this works here. All right. All right, here's my own meter.

And again, we're going to do a lab at the very end of this. And we're going to actually physically show you how to how to measure the resistor and this, this will come a lot clearer, I'm sure. All right now with a potential ometer. All right, the end points here, and here, stay the same. It's a fixed resistor. So if I go across the potential iometer at point A and point B.

All right. right there and right there, it will stay the same. And this is what I'm saying here. Okay? The resistance from A to B equals 10 k. Now, in this example and let's, let's, let's go back here. Let's go to the next slide here.

If you'll notice on the previous slide, I can turn the shaft this way. All right, so I can hold on just like a volume control. All right, Ah, well, a potentiometer is a volume control. So I can turn the shaft all the way. If I it's placed on a counterclockwise. I can take the shaft and turn it all the way clockwise.

Let's go back All right, the rotation from counterclockwise to clockwise on a standard potential ometer is 270 or 270 degrees, right here. All right. So now if I take the 10 K, right here, if I take the 10 K and divide that by 270 degrees, we get 37 ohms per degree. All right. Now what does that mean? Well, let's let's look at here.

Okay, let's, let's erase the Okay, so what's half Have 270 degrees? Well, that's 135. All right. And that's what I call the midpoint. Let me get my pointer. That's the center right here.

And I call that the midpoint. All right. So 135 times 37 ohms is a prop approximately equals to 5000 ohms. If you'll notice, originally, on our example, all right, the resistance from A to B is 10 K. So I find that the midpoint, all right, then the reason Distance from A to C is a, and his c would be 5000. And the resistance from B to C would be 5000. All right.

So basically what I'm doing is I'm taking and just regard this for a minute, let's, I'm taking disconnecting that there and putting a meter lead right here. And I'm measuring the resistance from A to C, this way. That would be 5000. And obviously, if I break the connection here, and measure from B to C, that would still be 5000 ohms. All right. So let's clear that Now, if my if I rotate clockwise 67 degrees and that's approximately three quarters.

Okay? A to see I'm sorry, that would be a quarter A to C would be 2500 ohms and B to C would be 7500. So as I as I move the rope if I move that shaft, basically what happens is that shaft turns the wiper here and that moves up and down. Alright, so the two end points A and C, A and B affects but I can change the resistance from Add a to c, or B to C. Okay, and the last example right here, rotation of 203, that now that's approximately three quarters clockwise, the resistance from A to C would be 7500. Okay, resistance from A to C would be 7500. And the resistance from B to C would be 25 on it.

But look, look at this if you haven't realized it already. Notice when I add up the resistance from A to C to BTC, in this example, it always has to equals 10,000 ohms or 10 k ohms. Alright, now I'm giving you a 10. An example of 10 k ohms in this in the slide, but potentially amateurs come in multiple, multiple multiple variable resistance. They come in one k two k 100, ohms, 500, ohms, 20, k 50 k. There's a variety of them. But they all work the same way.

If I have 100 K, all right, and it's a standard, potentially ometer, then I would take 270 degrees and divide that into the value of the potentiometer. And that would give me the ohmic value per degree. In this case, we're using 37 ohms per degree. All right, that is for a standard potential ometer. All right. So let's let's and I just want to add let's clear the slide here.

All right now Let's go back to this slide here. And notice I got a multi term potential winner right there. Well, this multi turn potentially Amina works the same way. As these guys here, the only difference is it were on a standard potentially ometer. It's 270 degrees for the center arm to go from here to here. On a multi turn potentiometer it may be 10 terms, five turns.

All right. So to go from, if it was, let's say it was a 10 turn 10 turn Potentially ometer. All right. If it was a 10 turn, going from here, from this guy he had going from here to here, I would have to rotate the shaft 10 times fully. What does that do for me? It gives me a finer adjustment.

It gives me a finer adjustment, if you look over here for was a conventional potential ometer Okay, and I could go from counterclockwise to clockwise and 270 degrees, then I get 37 ohms per degree. But what happens if I multiply that by 10. In this example, if I multiply that by 10 or divided by 10 or whatever, instead of being 37 ohms per degree, it would be 3.7 ohms. Actually, it'd be a lot less, because instead of going 270 degrees, we're going 360. So it would actually be less than 3.7 ohms. So I can get finer adjustments with a multi turn potentially on it.

Okay, and again, that may be used on a, if I'm doing a very precise calibration, or scientific applications where I have a circuit I've got to be very precise, then I may use a multimeter and potential there. All right. Okay, let's let's move on here. All right, continue on to how resistance to use part five