I thanks for watching this video that is made possible by our SES, the refrigeration service engineers Society. They have a very similar mission to what we have at HVAC school, which is helping to raise the quality of the trade through education. And I thank them for allowing me to use these presentations or excerpts from them for these training videos and you can purchase these presentations from their website in full. I'm just doing some small excerpts.

This one is on the core subject of electrical fundamentals, just some of the basic terms, a lot of technicians, struggle with electrical basics and that impacts their scores on a test. It also impacts their ability to communicate with other technicians. So it's really important in electrical that we use the right terms. Otherwise you're talking about somebody.

They think you're, saying one thing you're saying another which can result in misdiagnosis: it can result in unsafe conditions and so helping to just understand some basic terms and what they mean is what we're going to be focusing on here today. So we're gon na talk about voltage, we're gon na talk about ohms series circuits parallel circuits in power. There's gon na be a little bit of Ohm's law in here. I'm not gon na focus too much on making you do difficult, math and now you may need to do the math at some point, but I'm gon na more hopefully get you so that you understand some of these concepts a little better than maybe you did in The past one term that you may hear you may see is a column and a column is a measurement of electrical charges.

So it's the charge of six point two eight to the 18th power electrons, which is an enormous number that I don't even know how to read to you, because it's so long. But the point is: is that the Coulomb is a measurement of electrical charges, an actual measurement of a number of electron charges. When we talk about an amp or an ampere, an amp is defined as an electrical flow rate or current, and so when we say amp or ampere, that's a little bit more of a fancy way of saying it. We're really talking about a electron flow rate.

So you take a number of electrons the Coulomb and the flow rate is the amp and that's what we call current you're, going to notice that the definition of an ampere contains a quality measurement Coulomb in the combination with time measurement. So, from a very, very specific, the amp is defined as an electron flow rate equal to one Coulomb per second, so you have an out of electron charges. That's the Coulomb! You have a time that is per second that's. What an amp is you're gon na see that in some cases an amp is designated by an eye and sometimes it will be designated by an a if you've heard the basic.

You know Holmes law, it's e equals I times R and I is intensity. It's actually a French version of the word intensity and that's why we use I but you're gon na find more and more that a lot of charts and diagrams now refer to amps as a, but it could also refer to it as I so watch. For that. A volt is a measure of potential energy.

You've probably heard that before some people say electromotive force it's like the force or pressure. It's a measurement of this stored up energy and it's always between two points. We never measure voltage in terms of a single point. It's always between two points.

The actual definition is the measure of the potential energy contained in one Coulomb of charge. Voltage is also called electromotive force or potential difference like we mentioned, and it's the force or pressure that pushes electrons through an electrical circuit. People will use the symbol e to represent voltage and that you think of that as electro-motive force. That might be an easy way for you to remember that E is electromotive force, that's voltage, sometimes in certain diagrams and charts you may see it designated as V as well, but it is the force that's pushing those electrons from one place to another.

But again, it's always in terms of a differential I like to think in terms of a ball rolling down a hill high voltage goes to low voltage. You have to have a difference in potential energy for a ball to roll down a hill. There has to be a difference in gravitational energy between the valley and the top of the hill for the ball to roll down. In the same way, you have to have a difference in voltages for electron or electron charges to move from one point to another and that's what a volt is.

So, very simply, amperage is a quantity over time and a volt is a pressure measurement or a force. Measurement in an ohm is simply resistance, and so, when we say e equals, I times R. That means volts equals amp times. Ohms R is the resistance.

You'll. Also often see ohms designated by the Omega symbol, which is this symbol that you see on screen right here and ohm? Is the measure of resistance or opposition to the flow of current in a circuit? So voltage applied to a circuit produces a current that is limited by the resistance in the circuit. Without resistance, every electrical circuit would be short circuits, serving no useful purpose and drawing really high current. So when you take a battery and you connect from both sides with a wire - that's a short-circuit, because you don't have an appropriate resistance.

You don't have a load in the circuit, so electrical loads would be things like heating elements or light bulbs or motors or transformers and they're all going to have resistance. In fact, sometimes we will use the phrase impedance and that takes into account basic electrical resistance that occurs in something like a light bulb, as well as magnetic resistance that we call inductive loads like a electromagnet, a mode or something like that, and the term we use For that is inductive reactance, but when we mix all those resistances together, we either call that resistance, measured in ohms or impedance, measured in ohms without those loads that intentionally give resistance to the circuit. We would have unimpeded flow and really really high current. A simple way to think of this is: is that with no resistance, we have unlimited current the more the resistance increases, the lower the current decreases, and so you've maybe seen this there's an image out there.

That shows you no resistance is the is the clamping force, that's squeezing down preventing amps from moving preventing electrons from moving, and that is true when we increase resistance in a circuit, we decrease current so long as the voltage remains the same. If we increase voltage in a circuit and the resistance remains the same, then we increase the current. So current is the amount voltages the force. Ohms is the resistance against term conductor just means a material that allows electrons to flow easily.

It's a it's a material that has lower resistance, so a conductor has lower resistance, as opposed to an insulator that has more resistance, so very simply conductors are like copper, aluminum. A lot of metals are really good conductors because electrons can move freely across them. Now. The reason for that is kind of complicated we get into valence electrons and all that, but just basically to understand the term when something is a good conductor.

It means that it has lower resistance and allows electrons to move through it easily and thus wires are conductors. Insulators are materials that don't allow electrons to move freely and those are things like plastic or air or glass or rubber or ceramics, and so that's why you see wires that are covered in rubber or plastic with a conductor on the inside. They prevent the electrons from escaping the conductor and traveling into other conductors outside. So often we use insulators to prevent us from getting shocked or prevent electrons from moving places.

We don't want them to go now. We're gon na start talking a little bit more about voltage. Voltage is the electrical push that moves electrons through the circuit and really it is the electrons themselves. It's a difference in charges, it's a potential difference, but it's also an electro-motive force.

You may have seen promotive force designated as EMF before and that's what that means. Electro-Motive force the difference in force or potential difference between two different points, and that's why an electrical meter has two probes on it right. You have one probe to put in one point another probe to put in another point to see what the potential difference in voltage and force between those two points. Is you never take just one probe and connect it in order to measure voltage? It's always in between two different points, so mechanical analogy to this action when we think about voltage or current moving due to the force level is shown here, you have two water tanks connected by a pipe in a valve in the illustration, if first the valves closed And all the water is in tank a as you see here.

The water pressure across the valve is at its maximum because of that difference, and that would be like a higher voltage, a higher potential difference when the valve is open. The water flows through from pipe a to pie B until the water level becomes the same, and that would be the same as you now having the same voltages in two different points. You don't have a potential difference now, so, as you can see down here in the bottom, between tank a and tank B, you still have water in each tank. They're still in this metaphor, they're still electrons there, but the level is the same.

So the force is the same and therefore there's no flow versus before or there's a difference, a potential difference, and that is what provides the force for the water to move. So the water moving would be the current. Let's say I took that valve and rather than opening it all the way I just cracked it that would provide resistance to the flow of water that would be like ohms and then the difference in pressure between the two tanks. That would be like volts, so voltage again electrical push that moves electrons through a circuit.

We have different ways that voltage can be generated. Friction so a we all know static electricity when it's dry outside and if you take a balloon and you rub it on your hair. You'll see that static electricity, that's created because of friction pressure. If piezoelectric voltage can be produced by squeezing crystals of certain substances and again we're getting kind of fancy here, but it can happen, the heat you can produce voltage by by applying heat that would be like a thermocouple would be a really good example of that or A thermo-pile we use these to produce a small current in order to lock in a gas valve and say an old-school furnace or a gas fireplace something like that.

We still use from a couples and thermopiles light. You can use light via full photovoltaic reaction. Regular solar panels would be an example of creating a voltage or a potential difference with light, or if you have a light sensor that brings on a makes or breaks a switch when there is light or when there is no light. That would be another example of where you're using photo electricity chemical reaction.

We see this all the time in batteries, so batteries are an example of voltage being created because of a chemical reaction within the battery and then one of the most common. The type that we see in our homes and in our buildings is due to magnetism. We use generators at a power plant, a great distance away. That's then transmitted to us that we then use for everything that we do, and that, in fact is at scale the largest way that we currently are generating voltage, though photovoltaic or solar panels are becoming a more common source of voltage for everyday use.

Electrical current again is the number of electrons passing through a conductor and again there's a time factor that, like we saw, the Coulomb is used as a unit for measuring a quantity. But then current is that quantity moving over a period of time and that's what we management measure with an amp clamp when we take an amp clamp and we put it around a wire, that's what we're measuring is amperage or current direct current is a voltage that Causes electrons to flow in one direction. So when you have a potential difference, that's always moving in one direction. That would be direct current.

We often do that with batteries or with photovoltaic, like solar panels directly, it's direct current. So when you come directly out of a solar panel, it is direct current because there isn't this change, it's just going from one direction to the other until it's allowed to equalize, but more commonly. We see inside buildings in our equipment that we work on every day. We see alternating current, so alternating current has electrons flowing back and forth in opposing directions in North America.

That's 60 cycles per second, so 60 times per second, it changes from one direction to the other direction in the European Standard. That's 50 Hertz or 50 times per second that's produced by generators, and so that's the vast majority of the tricity that we see in homes and buildings and that we interact with in air-conditioning. Is this constantly changing alternating current and it's generated through electromagnetism? And so you actually have this rotating force. You have some sort of generator where something's rotating and it's creating this constantly changing magnetic field, which is why it goes on and off, because it's generated in a rotating field rather than in a single direction like a battery or a solar panel, Ohm's laws.

When you hear all the time so e equals I times, R is the most common that we say so. That's e is volts. Voltage equals amps times resistance, but it can also just as easily be said as amperage equals voltage divided by resistance or resistance equals voltage. Divided by amperage now, whereas Ohm's law is true, it's absolutely true.

There are many factors and in many cases, in real life, these things are changing all at once. So in the stake that's often made is people think that these stay fixed and they don't in reality, even something as simple as a light bulb. The resistance in that light bulb changes as the filament heats, and so none of these things are constant. You have to really understand the particular circuit you're working with, but it's helpful to understand how the math works.

The relationship between these things is named for its Discoverer 19th century German physician named Georg ohm Ohm's law states that the current in a circuit is directly proportional to the applied voltage and inversely abortional to the circuit resistance. Just a simple way of saying that, there's a relationship between all of these things - and it is always true - some people will say that Ohm's law doesn't work in real life and what they mean by that is is that in real life, you're very rarely going to Be calculating Ohm's law, but understanding the relationships between these things is a basic principle of electrical theory and knowing how to calculate it is something that may come up in a test. We look at this simple circuit here we have 10 volts DC and generally when we're looking at Ohm's law and we're doing the basic math we're generally gon na use, DC, Circuit's and resistive loads, because they're much more simple in linear. When you get into alternating current, you have something called power factors that comes in to the equation and then, when you have inductive loads, their resistance doesn't remain consistent.

Like I mentioned before, even a light bulb, the filament resistance doesn't stay consistent as that filament heats up. The resistance increases again when you're doing a simple calculation like the one shown here. This rarely comes up in real life as a practical calculation, but knowing how to do the math is simple. So all we do here is we have a fixed 10 volt source.

We have 2 ohms if we work homes law a equals. I times R I equals I times R. It would be very simple because the e in this case is 10, the R is 2 and so what times 2 equals 10. That's very simple: math, that's 5! So if all of this is true what's on the screen here, we would be drawing 5 amps at 2 ohms resistance with a 10 volt DC power supply.

You're often gon na see a chart that looks like this and it's simple as covering the part that you're wanting to solve, for so, let's say you're wanting to solve for the resistance. All you do. Is you divide the voltage by the current? The same is true of all of them. You just have you just cover the one that you're wanting to solve for so long as you have the other two then you're solving for the variable that you're, covering in this case, covering for resistance.

A series circuit is a circuit in which you're connecting multiple loads into one and out of the other in between power supply or a point of potential difference. So electrical circuits can be classified into three different categories: series circuits, parallel and series parallel, which is just a combination of a series circuit and a parallel circuit. A series circuit is characterized by the fact that it only has one path for current flow, but multiple loads. So multiple points of resistance, but only one path of current flow, so the rule on a series circuit is that the current is the same at any point in the series circuit.

So, no matter where you measure in the series circuit it's going to be the same, and the sum of the voltage drops across all of the components equals the applied voltage. So you have to look at the voltage drop across everything which would again be the entire circuit, and then you have to look at the sum of all the resistances. So the rule number 3 for a series circuit is the total resistance to current in a series circuit is equal to the sum of all of the resistances in the circuit. All that means is that in a series circuit, you just add up the resistances of all of the loads, all of the resistances within that circuit, and that is what your resistance is for calculation.

So the calculation is really really simple in a series circuit, and this is what that looks like you, only have one path for the electrons to move through in a series circuit here you can see this one path around this circuit and all you do is you Just take the resistances, you add them all up. The total voltage drop across the entire circuit is all that matters. You have to calculate the differing voltage drops across each one. It's just the total voltage.

That's ten volts DC in this case we've got 20 total ohms. What would that equal 10 because e equals I times R? So if we go back we're trying to solve for the current we're going to go with that middle one there, so I equals e divided by RI equals e, I'm covering I equals e divided by R. If E is 10, volts and R is 20, and what does that leave us with leaves us with 0.5? In this case, the e is 10, the R is 20, and so therefore, the eye or the amperage is going to be 0.5. So a parallel circuit is a little different in a parallel circuit.

Each individual load is connected across the potential difference itself and I'm going to show you what that looks like here in a second, but it has more than one path in between the points of potential difference, so the total current flow. These are the rules. The total current flow on a parallel circuit is the sum of the currents through the individual paths or branches, and so we work with parallel circuits all the time. In fact, if we had series circuits in our homes pretty much all of the loads or things that do something in our houses, our lights, our oven, coils, our motors, everything that we see in our homes and buildings are going to be parallel circuits because if they Weren't then you'd have all of these varying voltages.

Each particular load is connected in between the points of differential energy or the points of potential difference in the circuit and I'll show you what that looks like here in a second. The total current flow in a parallel circuit is the sum this is rule number one. The total current flow on a parallel circuit is the sum of the currents through the individual paths or branches rule number two. Each path and a parallel circuit has the same potential across it so because they're connected from one side of the power supply to the other side of the power supply, each particular path has the entire applied voltage across it.

Now, here's where it gets weird and we're gon na use the word reciprocal, which even I have a little bit of a difficulty with the reciprocal of the total resistance of a parallel circuit, is equal to the sum of the reciprocals of the individual resistances. And let me make this really simple, and that is in the same way that in a series circuit, we add up the resistances, meaning that all of the resistances together are greater than any one resistance in a parallel circuit. It decreases the total resistance because you're adding more paths, it's just like. If you had a river and you forced it through this really narrow gap, you would say that there's greater resistance to the flow.

If you gave it a bunch of paths that that river could take, it would be easier for it to flow through all those paths, there'd be less resistance, and so what happens is when we add in additional parallel circuits, we decrease the overall resistance of the circuit And I'll show you how to do that reciprocal math for a parallel circuit. So this is what multiple paths look like so rather than that current having to flow through every single one of these in order to make it around the circuit. It flow has individual paths in order to make it to either side and so that 10 volts DC present every single one of those and there's several different ways. You can do the math on this.

You can calculate the current in each individual path, which is fairly simple, so we'll just use our three as an example. Our three is twenty ohms, it's the same as the other one that we calculated that other series circuit, and so that's going to be 0.5 amps for that particular circuit. Well, the next one is 2 ohms. So that's going to have 10 times the current, because it's lower resistance so that, rather than being 0.5, is going to be 5 amps.

So now, between those two we have 5.5 and now all that we have left is that 4 amp circuit that one's a little trickier. But again we know that it's going to be half of what the 2 ohm circuit is. We already did that math. So now we have 0.5, we have 5.5 and then we have 2.5 amps on the 4 ohm circuit.

That would be a total of 8 amps in this circuit again, because we're treating each circuit individually in a parallel circuit, because we calculated that 8 amps would be the total circuit current now, all we have to do is work backwards. So if now we're trying to solve for resistance, we're covering the resistance right here and we're dividing our e, which is 10 volts by 8, which is our current, and that gives us what our total circuit resistance is, which is lower than any one of the resistances. That were shown in that parallel circuit. Prior to that, in fact, I have to get at the calculator to tell you what that is so 10 divided by 8 is 1.25 ohms of resistance.

You can see here that's lower than any of the single circuit resistances, because the sum of the resistances in a parallel circuit results in a lower total circuit resistance. Because now you have multiple parallel paths and again from a practical standpoint. You're very rarely going to have to do that. Math but understanding the relationships is important, especially when you're taking your tests to get the answer right, but also because it gives you that confidence to understand the difference electrically between parallel circuits and series circuits and again Ohm's law still holds true.

You have lower resistance when the voltage stays the same. You have higher current and that's what you see here in this parallel circuit. You have higher current here because you have lower resistance due to multiple parallel paths versus a series circuit where that current has to travel through all of the resistances. More resistance means less current.

In the case of a series, parallel circuit, it's just a combination of parallel circuits and a series circuit in the case of the series circuit, you really treat it as, though in the series portion of the circuit when you're looking at the total. You really just add together the two series circuits, so this portion of the path is actually 12 ohms, because it's two six ohm resistors in series with each other, and then you have additional parallel paths. Now, if you want to calculate the voltage drops across each one, that gets a little more complicated we're not going to do that in this video. It's hard to do.

Math like this without actually practicing it. So, in order to understand some of these things like calculating voltage, drops you're going to want to get out a pad of paper and actually do the calculations yourself, but just know that in the series circuit you add together the resistances in a parallel circuit. You add together the currents, so I'm gon na say that again in a series circuit, you add the resistances all up in a parallel circuit. You add together the current or the amps.

The next thing is work, often called power or wattage people get this sometimes confused with amperage, where amperage actually has to have the force calculation mixed in there in order to come up with wattage. So work is performed anytime. That force causes motion specifically voltage causes electrons to move or flow from one point to another in an electrical circuit. That's what we're talking about here.

The flow of electrons through the load of a circuit requires electrical energy to make that happen, and then you actually have work done. Work in the form of heat work in the form of motion work in the form of something in the load and in the connecting circuits there is work being done and that work is what we call power or wattage. We measure it in kilowatts. We measure in Watts, when we say kilowatt, we're just saying a thousand watts, in fact a little light back here when you say kilo pretty much anything you're saying thousand times we represent that by power and that's what we call watts law, which is actually a rule That you're gon na use more in the field than Ohm's law.

It's very rare that you're going to measure the resistance of something to calculate Ohm's law, but what's law, you're gon na use quite often because what that means is power or wattage. So wattage is designated by P here equals E times I. So it's e and I you've already learned that's volts times amps. That comes in handy because, if you wanted to say say you wanted to calculate the wattage of a compressor, you would take the voltage applied to it and you would multiply that times the amperage that would equal the wattage.

Now I'm I left one little part out. You also have to multiply times the power factor in an alternating current circuit, but often that's not a huge. That's, not gon na make a huge variation. Generally speaking, when we're calculating in the field, we literally just take our voltage.

We multiply that times our amperage, and that gives us our P or our wattage. If we want to calculate kilowatts, we just divide by a thousand which we can then take and figure out something like kilowatt hours, to look at what a particular appliance is costs to operate. So that's a very practical thing that you're gon na find that you do have to do, but it from it from a technical standpoint, because this does come up in tests, and this is a good thing to know when electricity is doing work in a DC circuit And we specify DC because otherwise an alternating current you get the power factor, one volt, causing a current of 1 amp through a circuit results in the release of 1 watt, second of energy, for every second, that the current flows and again, we there's this time factor Here, because, in the same way, if it's a kilowatt hour, we have to know how long is it happening, but it's still very simply P equals E times I or a Watts equals volts times. Amps, that's one that comes in really handy and often is going to be on the test.

So that's it. We talked about some electrical terms, voltage, Ohm's law series and parallel circuits and power. These are the sorts of things that, until you actually do, some of the math you're, probably gon na struggle with it. You actually have to sit down and and do some of these questions, I would suggest that you take some practice exams, there's many of them that are available depending on who you're taking the NAIT exam through.

I would suggest that you read the RSES guides preparing you for an 8 as well as the one that Nate has produced themselves and become an our SES member. That way, you can get a lot of free education like this on a more regular basis. Hope you found that helpful, we'll see you on the next video.