There's true ways like electrically of talking about these things and then there's ways that serve you so that you can be a good diagnostician to build up a circuit is a load really a separation point between the two halves of the circuit it's still connected, but it Does create resistance, and so, as far as we're concerned, you have to run a circuit between a load and the load. Is that kind of point of separation so that if I read because we're talking practically using a voltmeter here, if I take a voltmeter - and I read between these two points, what am I gon na read one or a zero, because it's these two points are connected Directly to each other, if I read across the closed switch, what am I gon na? Read? I'm gon na read zero because the switch is closed. A switch doesn't do any work. Switch is just making a circuit.

It's just like it's just like reading across a wire. If I take this contactor and this contactor is closed and I take a voltmeter - and I read across it like this, I'm gon na read nothing. It doesn't matter if voltage is applied or not. I'm gon na read nothing because electrically.

The two halves of that contactor are the same they've been connected to each other. Now, if I take a if I if this switch is closed, and I take a meter - and I read from here to here - what am I gon na read on 120 volt circuit, I'm gon na read a hundred twenty volts because I'm wiring in my meter, like A load in between the two halves of that circuit, but it's because this load exists. If that load didn't exist. What would happen as soon as I apply power? Is? It would immediately short out immediately either trip a breaker blow a fuse or catch something on fire, because the load acts as that restrictor.

If you will, it adds that resistance into the circuit that controls the flow of electrons without a load in the circuit to separate the two halves you have uncontrolled current flow. Now again, this isn't a we've done. So many of these basics classes that I'm not gon na go into the basics of what is voltage. What is amperage we're not gon na do that today.

So I am making an assumption that you understand some of those things. So you don't. You can't have uncontrolled flow. Uncontrolled flow is prevented by the load which restricts does work, but it also controls the flow of electrons quick question.

Just quick pop quiz, higher resistance equals lower or higher amperage higher resistance equals lower or higher amperage. I'm looking for everybody to answer this. The answer is lower. Very simple resistance to the motion of electrons equals less electrons moving right, it's a very easy thing to get your head around you're, resisting it therefore fewer of the move.

Therefore, you have less current. So if you have no resistance, because it's just a wire or very very little resistance, then there's going to be very little there's little to nothing, holding back those electrons and with little to nothing holding back those electrons. The amperage goes sky-high when the amperage goes sky-high. The heat in the circuit goes sky-high and you melt the wire or whatever else right it makes sense.

Are there? Is there anybody in the room? Who has a question about that? Because this is an oft disputed topic, all right, we'll move on, because it actually is a fairly complicated topic when you get into it any further than that. But as far as the circuit is concerned, when there's lower resistance in the circuit there's higher amperage, when there's higher resistance in the circuit, there's lower amperage got that and the load is what is designed to provide resistance in the circuit. Now, what are some ways that you could add resistance to a circuit in an undesigned manner? You could add too many switches switches in and of themselves shouldn't have resistance like they're not designed to, but they can over time switches that open and close - and I mean you see this with safeties that are that are opening and closing, because you say you have A furnace and the furnaces you know going out on high temperature, so when that's happening or it's rolling out and as a roll out switch, is opening and closing over time those switches are arcing and as they arc, they build up resistance in them, because carbon builds Up on the contact points, and so eventually the switches themselves become little loads and start to add resistance into the circuit as well, which causes all kinds of problems. You can add resistance in a circuit by having a contactor, where the points get pitted and nasty on it.

That adds resistance because, while it's supposed to close and make perfect contact over time, it stops making perfect contact because there's carbon and crap that's builds up in there ants crawl in your contactor, that's a perfect example: they start to build up their little bodies as they Get crushed and decimated become little resistors in your in your contactor circuit. So that's resistance, that's not design! If you don't, if you don't torque down a wire properly, you leave a wire loose and it's sitting in there arcing that's resistance, that's not designed, because the only place that resistance is designed in the circuit is where the load and when we read across the load. When the circuit is energized, that's when we read our applied voltage across the load, which is why, if I'm, if I ask you to, does that, does the contactor have 24 volts? What I'm asking you is on the coil of the contactor? That's the load! That's the part that does work of pulling the contactor and selectra magnet. Do we have 24 volts applied across the load? If you take the line going into the contactor, and just like just like with the light - and you read in in between any two points that are electrically the same you're gon na read nothing no matter whether this switch is open or closed.

But actually that's not true, but every on the other side that will get into that a second. But if I read another two Electrical points that are exactly the same you're gon na read zero and it doesn't matter if there's electrical potential there or not because remember potential. It's in other word for voltage. That just means there's the potential to do work.

There's a charge that exists there, but it doesn't mean that it's actually doing anything right and in order to wire in a voltmeter in such a way that you're gon na read something you've got to wire it in just like you're wearing in a light bulb to Make it light up and if I take a light, bulb and I take the light bulb - and I wear it in like this - is that light bulb gon na light up? No because I'm connecting the two leads of the light bulb because again, every load has two wires has two connection points, I'm connecting them to two points that have no difference in charges. I've got to connect in between two points that have a difference in charges right, which then brings me to what I just spoke improperly there, which is if I've got a switch. So let's say let's say that we've will put it we'll put a motor here. Just a simple shade poll motor with a normally open, switch all right.

Now it's $ 120 k't. This is neutral, so this is the line set of the switch. This is the load side of the switch. This is the load.

This is neutral now I'm gon na use my fingers and my fingers. Our meter leads right and I'm gon na put him different places and tell me with everything being as it's shown here, what we're gon na read. So just as shown, you see the switch. It's normally open it's drawn as open.

Okay, you with me. So what happens? If I read between here and here, what do I read? I read a hundred twenty volts. What happens if I read between here and here? What do I read right: zero, they're electrically, the same right. What happens if I read between here and here? What do I read zero? What happens if I read between here and here? What do I read? What happens if I read between here and here? What do I read? Okay, that's correct! You do read 120, but why do you read 120 between here and here, because there is a difference in potential between this point and this point that load is in the circuit.

Now, when I connect my meter in, will that motor start running no, because that's not how that works, I'm not gon na go into why but you're going to just understand this understand. Just just just take this and put it in your brain without going into all of the back theory about this, you will read the total applied voltage when you read across the load now right now, if I read from here to here, I'm gon na read what 0, because the switch is open, so there is no applied voltage across the load right. If I read across an open switch, I'm going to read the applied voltage on that circuit, so long as the rest of the circuit is intact. This is sort of a trick.

Question because, let's imagine, which is why reading across an open switch, is a it's, it's not a bad test, but it can be. It can get you in trouble, sometimes let's say so. They get to open switches. So I read across here now.

What am I gon na read zero right and if I just give you the rule that reading across an open switch gives you the applied voltage, that's gon na kind of trick. You because I mean I I have potential here, but I'm still not gon na, read it because the rest of the circuit isn't intact, so the rest of the circuit has to be intact for that test to work. Well, if you test the ground but again, testing the ground is very fickle because you're relying on something when you test the ground. What are you relying on you're, relying on the fact that the ground is actually properly connected and that's tricky because it isn't always the case now? Should it be? Yes? Is it a valid test? Yes, but it's not a valid test in this particular application.

A better way to do it is to walk through the circuit, so that would mean I take my black lead and I go home and I leave it there. How much? What will I read? What will I read so I know the switch is open. I know this switch is open right. That's that's a really good way to use a voltmeter to diagnose a circuit.

You pay your one side to to a known opposite of where of the of the line set coming in which you know a neutral ground. L2. Whatever you want to call it, you just pay get there, and then you walk through the circuit and see where you lose as soon as you lose voltage now you know that's where the circuit opened.