Transcripts
1. 0 Welcome and Introduction: Welcome Toe Homes Law made easy for D. C Series circuits By the end of this course, students will be comfortable with OEMs Law and the Serie Circuit rules and math calculations for just about any automotive or basic D C theory circuits. If you struggled in school to learn this topic, press the buy button as soon as possible. My goal is that you will struggle no more. Holmes Law expresses the relationship between voltage current and resistance in electrical or electronic circuit by knowing any two values. Voltage and current voltage and resistance were current and resistance. The third value can be calculated mathematically. This course is geared toward automotive students beginning Elektronik students and do it yourselfers that desire a solid foundation and understanding of D C series circuits and OEMs law. This course does more than just show you a formula and tell you about a concept. It walks you through the thought process, the steps and the reasoning behind them. It provides many practice examples and detailed explanations of how the answers were calculated and determined. Oftentimes, engineering programs try to deliver way too much content, give very little detail and provide very few examples I will cut to the chase for you and focus on the information and skills that are most needed to master this topic. When done with this course, keep an eye out for my follow up courses on parallel D C circuits and Siri's parallel D C circuits, which will be coming out soon. Let's get started.
2. 1 Basic Electrical Keywords to Know: before we get started with owns law, let's go over some basic electrical keywords in terms that are very helpful to know to help you understand homes law better. A series circuit is a circuit that just has one path. A parallel circuit has more than one path, and a Siri's parallel circuit is just a combination of the two in automotive circuits. Most circuits are parallel, but some of the circuits that they use for perhaps daytime running lights might be serious circuits, and we'll learn more about why they would want to use Parallel versus Siris in automotive circuits in a later lesson. Voltages. Electrical pressure. It's measured in volts, and it's represented by the Symbol E when we're doing our calculations and just note that some books use the symbol V, but in this course, we're gonna use the symbol E. Other names for voltage would be electro motive Force E. M. F, which is just abbreviation for that and difference in potential when you're using a volt meter, you're actually measuring the difference in potential between two points where you put the leads and that becomes your voltage measurement. Current is the actual flow of electricity or flow of electrons and current is measured in amps, and it's represented by the symbol I and note again that some books use the symbol. A. Oftentimes, if they're using V for voltage, they'll use a for current. But like I said, in this course, we're going to use E for voltage I for current and are for resistance, and the calculations will be the same. It's just that there were two ways of doing it, and some people like keeping it one way, and other people like the other symbols. I found that E I and our work best for me, and that's the way I'm going to teach it to you. And you could easily substitute the other two symbols the V in the A, and it wouldn't change anything that you've learned in this course. Resistance is the opposition to current flow, and resistance is measured in homes. And, like I said, it's represented by the symbol are power is the rate that electrical energy is transferred by an electrical circuit. It's measured in Watts, and it's represented by the symbol P, and there's a formula for power which will learn in a later lesson. But Basically, the formula is P. Power equals I current times e voltage. And like I said, we'll learn that relationship and do some calculations with it. It a later lesson voltage drop is the amount of voltage used by a component or part of the circuit, and we use a volt meter to make a measurement of voltage to find out how much that voltages and by understanding OEMs law will know ahead of time approximately what we expect to measure. And if we were testing the circuit, we would be expecting a certain measurement, and then we'd be using the meter to decide if we got that measurement, and getting the correct measurement would lead us a certain path and diagnosis, and getting the wrong measurement would lead us to a different path of diagnosing. Ah, conductor is a substance that makes it easy for current flow. Examples would be gold, copper, silver steel. Anything that will allow current to flow more easily is considered a conductor. On the other hand, an insulate ER is a substance that does not allow electricity to flow easily, and examples of insulators would be rubber, plastic glass, dry wood and if you think about what's on your electric cords in the house. They have a rubber or plastic that's there as an insulator so that you don't touch the electrical part of the copper that's inside of there. There's two common types of wire that's used in electrical circuits, and one of them is solid wire and the other one is stranded. And the solid wire just means there's one piece of copper going through the insulation, and the stranded wire just means that there's a bunch of strands of copper next to each other going through the insulation and the advantage of solid wire is usually it can carry more current for the same physical size if we used solid versus stranded. But the benefit of stranded wire would be that it's more flexible because it's using those smaller strands of wire when you go to bend the wire. If the wire needs to move or wiggle back and forth during the operation of the device, stranded wire is less susceptible to breakage because it has flexibility inside the insulation where solid wire has much less flexibility in our last two terms are alternating current and direct current, now alternating current is what's used in your home, where its current, that's reversing its direction. It means the electrons air flowing one way, and then they're flowing the other way and then back to the first way and then back to the second way. The current is just vibrating back and forth. If you looked on an electrical device, it would say in in North America with, say, 60 hertz, which means 60 times per second. And the difference between that and direct current direct current, which is what is produced by a battery. You have a surplus of electrons on one pole of the battery or one post of the battery, and they move from one side to the other side from the negative where there's the surplus of electrons to the positive, and once the battery is balanced back out, then the battery is considered dead or in need of recharge. So when they construct batteries, they use some type of a chemical reaction that takes the electrons off of the one plate and move them to the other plate, the negative plate, and then when you hook a circuit up to it, you're actually just giving a path for those electrons to go back from the negative to the positive. So these are the basic definitions that will just get you started. It's helpful to understand what these are, and some of them were gonna go into great detail in and others. We may just mention here and there as we progress through the course, because this course is mostly going to be about homes law and exploring the math behind it and how to calculate the different values of voltage, current and resistance in the different types of circuits. So in the next video, we'll learn about homes law and the three formulas that we use to make our calculations.
3. 2 Ohms Law Formulas: Holmes law is just three simple formulas, and it's really just one formula. Written three different ways depending on which you're trying to solve for in a circuit where we have voltage, current and resistance. If we know two of the components of the circuit voltage and current or voltage and resistance or resistance and current, we can calculate the 3rd 1 homes Law gives us that relationship. So if I'm trying to calculate E and I know I and are the formula would be equals, I times are if I'm trying to calculate the current I and I know E and R then the formula is I equals e divided by r from looking for our and I know e and I the voltage and current then the formula is r equals e divided by I. Now that all sounds like how am I gonna remember all of that? And there's actually a gnomes law, a triangle that makes it easy to remember how these formulas go. So to use this triangle, you just cover up the one that your trying to calculate. So if I'm trying to calculate e, I would cover that up and I would be left with I and are on the bottom. So if I want to find E, it would be I times are. And if I'm looking for I I would cover up the I and I would be left with e divided by r, which is giving me the calculation to get I and the same thing with resistance. If I'm trying to calculate the resistance, I cover up the r. And it reminds me that the formula for our is e divided by I take a look where I've written I and our two different ways the formulas. And in this course, we're gonna use the slash line to mean the divided by because that's what's commonly used and it's just easier to be consistent. So I wanted to show you the divided by in the first set of formulas. But from now on, when we're doing division, we're going to do e with slash meaning divided by r and will use the X for the times like is normal. So this will be our three OEMs law. Formula Z equals I times are hi equals e divided by r and r equals e divided by I and remember you cover up the one you're trying to get. If I'm trying to get E I cover up the E and it's I times are if I'm trying to get high, I cover up the I and it's e divided by R. And if I'm trying to calculate our I cover up the R and the formula would be e divided by I in the next video, we're going to just give a simple explanation of what OEMs law is in words. So you can understand why you're doing all of this in the first place, so I'll see you in the next video.
4. 3 What Does Ohms Law Mean: Let's explain in this video what homes law is all about. It really just means that if the voltage increases and resistance stays the same, the current will increase. Think of this as your garden hose if voltages, the pressure and resistance is the restriction. If I was to turn up the knob on the hose to allow more pressure, as long as the hose diameter stayed the same, if I put more pressure, I would get more flow. And current is the flow, so all it means electrically is the same thing. If we increase the pressure where the voltage and the restriction or resistance stays the same, then the flow of electricity will increase, which is the current and the other part of homes law if the pressure stays the same. So let's say I have the pressure on halfway on my garden hose. If I was to compare my regular garden hose and then switch to a more narrow or a smaller diameter garden hose, I would get less current flow or less water flow out of it. So all homes law is stating is that if the electrical pressure or voltage stays the same and the restriction increases or gets bigger, it will be harder for current to flow, so current has to go down. And those are really the only two things that you need to worry about. And the formulas will calculate what the different parts of the circuit are like, what the voltage is in a certain part of the circuit with the current is and what the resistance is in a nutshell. These two statements are what owns law is really about. So let's see if we can simplify those statements a little bit more. Let's say instead if e or voltage goes up, I or current goes up, and if our the resistance goes up, I the current would go down. It's pretty much saying the same thing. So let's simplify it even further just so we can have something that we can visualize in our head and memorize it. And then it will stay with this for whenever we need it. So now down here on the bottom, I've just simplified it even further. If e is up, then I goes up. If our goes up, then I goes down. So if the voltage goes up, the current goes up If the resistance goes up, the current goes down, and that's pretty much all homes Law is about. Now let's put a little math to that current formula. Let's look at just this middle formula. I equals e divided by r, and we'll put some numbers to it so that we can show that this is what would happen. So let's say that the voltages six volts is six, and the resistance is to homes. Are is too. So to do the math I equals e divided by r equals six divided by two hi or the current would be three amps. So now let's take our homes law information and let's say what would happen to the current the three amps of current if the voltage e instead of being six if it went up to eight. So if he went up to eight and are was still too, then current would go up to four AM's because now it's e divided by r eight. Divided by two is four amps. So if the voltage goes up, the current goes up. And what if instead we change the resistance, so he is still It's six and are was at two, and that gave us three amps. But what if our or the resistance increases to three homes? So now I'm gonna have six volts divided by three homes, and the total current would be too. So the current would decrease. So homes lodges makes these statements and its defining this mathematical relationship between voltage, current and resistance and the OEMs law formulas are just giving this away to make the calculations. In the next video, we're gonna practice working with the OEMs law formula just for some simple math practice, and then we'll move on to applying them to Siri's circuits. So I'll see you in the next video.
5. 4 Ohms Law Math Practice: before we start using OEMs law on Siri's and parallel circuits. Let's practice some of the math by doing a few examples in each example, too of thieve arable zehr given like either voltage and resistance or voltage and current or current and resistance. And you have to calculate the one that's missing. And I found from teaching students over the years that when you're first starting out, it's better to write the formula down and then plug in the numbers and then get your answer . So for the 1st 1 you would write, I equals and then write out the formula and then put equals and then put the numbers that go into the formula and then put your answer. This would give you the best way of learning and retaining it. It also lets you avoid making common mistakes that people make by just taking the small number and dividing it into the big number that they see when they're given the two variables. Like if they're given 24 4 A lot of people, without even looking at what the formula is, would just say 0 24 divided by four. In some cases that would work out. But in other cases, depending on what the two readings actually are, it may not be the right formula to just put the small number into a large number. So if you write out what the formula is, especially in the beginning, that you'll have it down much better and you'll avoid making mistakes so you can print out this worksheet that's available in the additional Resource is, and I've also made it available with the OEMs Law triangle and the formulas written down so you can print it out either this way, and try and work from your memory of what the formulas are. Or you can print it out with the OEMs Law triangle and do the same thing. So let's move it to the side for a second. Give us some room to put the OEMs like triangle down, and I have identified the formulas for you in case you want to do it. This way, you can also print out this sheet in the available resource is for this lesson. So spend a few minutes figuring these out, and we'll go over them in the next video
6. 5 Ohms Law Math Practice Review: So let's review the OEMs law practice examples for number one. They're giving you the resistance of 12 homes and the voltage of 18 volts, so the formula for I or current is equal to e divided by R. And if we plug in the numbers, it's 18 divided by 12 and then the answer is 1.5 amps. I find it's best if you'd write out the formula and then plug in the numbers. Like I said in the last video. And then when you're putting your answer, the 1.5 right out the word amps and if its OEMs or volts or whatever it is, if you do that, especially in the beginning, then it'll solidify in your memory what each one is. Ease. Volts are was resistance, and I is current measured in amps, and you'll have that in your head and you'll never lose it just by doing a little repetition and a little extra writing, especially in the beginning, it's well worth it. So for number two, they're giving you the voltage. He's 24 eyes. The current eyes four amps. If I was to write out the formula for resistance, it would be e divided by I. When I plug in the numbers, it's 24 divided by four, and then the answer to Number two is six homes for number three. The current is 12 amps in the voltages 60 volts. The formula for resistance again is he divided by I. I plug in the numbers. It's 60 divided by 12 and in this case it equals five homes. The number four. They're giving you the current 16 amps, and they're giving you the resistance 12 owns, and then the formula for voltage e equals a times are you Plug in the numbers. It would be 16 times 12 and in this example, the total voltage would be 192 volts. For number five. The resistance is 50.5 homes, and sometimes you'll see it written as just 0.5, and sometimes people will ride 0.5. In this case, it's showing 0.5, but it's the same number, and the voltage E is 36. Bolts the formula for current I equals E divided by r, and that's 36 divided by 360.5 and it's 72 amps. And then for the last one we're trying to find e again. The resistance value they're giving us is 1.5. The current is four amps. The formula for E is I. Times are, and then it's four times the 1.5 people six volts. It becomes very simple. Once you understand which formula to use and then just to plug in the numbers and make the calculation, the OEMs law math itself can be relatively easy to master.
7. 6 Ohms Law For Each Part of the Circuit: Now that we understand what homes law is and how to use the three formulas, let's take it to the next level when we're talking about voltage, current and resistance. Sometimes we're talking about the total voltage, current and resistance of the circuit, and you will see that as e. I and our. But sometimes you will see it as E. T. I T and RT, meaning the total voltage, the total current and the total resistance. But what if you needed to know how much voltage was being used by the first resistor or the first load in the circuit? It wouldn't be the same as the total voltage, especially in a series circuit. So in this case, you would need to know the voltage for resistor one, the current for resistor one and the resistance of resistor. One. What if you wanted to know the same information for resistor to that would be represented by e to I to and are too. And if there's 1/3 resistor or 1/4 resistor, then you would have even another set e three i three r three e four i four are for so depending on how many loads air in the circuit. You could have quite a few calculations that you would have to make, but the math stays the same simple math that we did in the last lesson. It's just e I and are. And if you know two things, you can calculate the 3rd 1 Now. What you can't do is use I four to get E two or I three to get E one or E. T. To get our one, you have to stay consistent. You have to stay with all of the information for resistor to resist or three resisted. Four. And the formulas will only work if you're using the information that's for that resistor or for the total resistance, current and voltage, you would have to use the values of the total voltage, the total current and the total resistance if you were making calculations, so let's see what that would look like on a series circuit. Let's bring up a simple Siri circuit with three loads. If I was making owns law calculations to find the total voltage, the total resistance where the total current I would use the OEMs law formula and if I knew two pieces of information I could calculate the 3rd 1 The same thing goes for resistor. Number one. If I knew two pieces of information about resistor one like if I knew the value of the resistance and I knew the current or if I knew the value of the resistance and I knew the voltage, then I could calculate the 3rd 1 What about resistor to It's the same thing. There's three pieces of information there, and I'd need two of those pieces of information if I was going to do any math. And there's no difference for resistor number three. So with OEMs law, we had three variables which were E. I and our. But now we have three variables and depending on how many loads in the circuit, you may have to make in this case 12 calculations, although some of the information is going to be given to you. If you were doing the gnomes law problem, and then you would have to figure out the rest of them. But there's three formulas for each location in the circuit, and if I tried to label the formulas on the circuit, it would look something like this before we can go ahead and do some practice examples on Syria's circuits. We do have to learn the Siri's rules because there are times where you don't have enough information to do any math. And you have to use your knowledge of the Siri's rules to get you the additional information that you need. So in the next few lessons, we're going to cover the Siri's roles in detail so that you know what they are. And then we're going to tackle some Siri's circuit math examples where we will use either the Siri's rules or our knowledge of OEMs law and applying it to the proper part of the circuit so that we can get any answer that we need. So let's move on to the Siri's rules.
8. 7 Series Circuit Rules: here are the four Serie Circuit rules in this video. I'm just gonna briefly cover and explain the four rules. And then there'll be a short video explaining each rule using the schematic so that you can understand them better. The rules are also available for download in. The additional resource is this is something that it would be a good idea to try to memorize them. But as you'll see, the words don't have to be exact. You just have to understand the concept. So rule number one current remains constant throughout the circuit. It just means that once the value of the current is determined based on the voltage and the total resistance in the circuit, no matter where in the circuit you measure it, it's gonna be the same value. So what this is essentially saying is that if you knew, I total you would also know I one and I two and I three if there's three resistors in the circuit. So if you were doing a problem that you were given to solve her owns law in a series circuit, If they gave you on Lee, I too you would know I won I three and I total Why? Because current remains constant. So as long as you know one of them, you know all of them. Rule number two. The total circuit resistance is the sum of all resistance in the circuit. And all this means is that if there's three resistors in the circuit, it means that our one plus r two plus r three equals the total resistance. And keep in mind that these 1st 2 statements that we've made apply for Siri circuits. Parallel circuits have different rules. Holmes loss still gonna be the same, but the rules will be different, and there's only four of them for Siri's and four of them. For parallel rule number three, the sum of all voltage drops is equal to the source voltage. For example, if the source voltage is 12 it will all get used up by all of the different loads in the circuit. So if there are three loads in the circuit, they will add up to the total amount of voltage, which in this example is 12 and Rule number four is stating that the voltage drop across each resistor will differ depending on the value of the resistor. It just means that if the resistor values air different, then they'll use up the voltage by proportion to their resistance. If I had to six own resistors in the Serie Circuit, they would share the voltage equally. If I had a seven home and a four ohm resistor with seven home would get proportionally more than the four own would if I had a 10 home and a one home and another one ohm resistor. The 10 ohm resistor would get most of the voltage and the 21 ohm resistors would get the rest and they would both get the same amount because they're both the same resistance. But they would be substantially less than the 10 ohm resistor uses up. But keep in mind that the sum of all voltage drops will still equal the source voltage, even if the resistor values air different. So in the next few videos, we're gonna take one role at a time and apply it to a circuit so that we can cement into our memory what these rules mean, so that will be able to use this information to analyse a schematic, to make a decision as to whether we're supposed to be measuring 12 volts or six volts, or between 12 and six. If it's sharing with three separate loads, maybe you expect to measure four volts. Having all of this information in your head gives you a way of deciding approximately what the voltage should be just by looking at the schematic and knowing what some of the values are by putting them into a separate video. Each one will be easily accessible if you need to review specific information about any of the rules.
9. 8 Series Rule 1 Current Remains Constant: Let's go into more detail about series circuit rule number one current remains constant throughout the circuit. An and meter, which I have as a circle in the circuit path labeled with a is like a counter. And it's just counting the amount of current flow that is going past that point. So I total would be what this meter over here is. Measuring I want is the current that's leaving resistor one by two is the current that's leaving resistor two and I three is the current that's leaving resist or three. And since Siri's rule number one says current remains constant throughout the circuit, the total current would not be two plus two plus two. The total current would be, too. It would be two amps. And why would it be, too? Because it's just a count of how much current has left based on the characteristics and the values in the circuit and how much current is following this one path. And since there's only one path, the current can't go anywhere else. Just think of it as counting people. If the and meter was like a hall monitor watching how many people walked down the hall and there was only one path that students can take. When they went on their break, they had to go down this hallway and then this hallway and then this hallway, and they could only go in one direction and they had to come back to the classroom. And if there was a teacher in these four locations counting how many students went by, they would have to get the same count in all four locations because there was no other place to go. And it's very similar in a Serie circuit. All it is is once they determine what the total current is based on the voltage and the resistance, then I would be able to answer any of the currents in a series circuit. So in this case, the total current I t. Is two amps. But what if they gave me I t and didn't give me any of the other ones? Siri's Rule number one is telling us that if you know any one of the currents, then you know all of them as long as it's a serious circuit. So if they gave me on Lee I to and they didn't give me, I won and I three or I total using Siri's rule number one. I would then be able to realize that all of the eyes were the same and I could fill those in. And then I would be able to do more math. And as you'll learn when we do the Siri's examples, it will not matter how difficult the example is. What matters is that you understand when to do math and when to use a rule. And when I show it to you in the later lesson, you'll find out that your understanding of the rules and your understanding of the math once you have those down, there's no Siri's example that they can give you that is solvable, that you won't be able to sell. So let's move on to rule number two.
10. 9 Series Rule 2 Total Resistance is sum of All Restistance in the Cicuit: Siri's rule number two says that the total circuit resistance is the sum of all the resistance in the circuit. All this means is that if I wanted to find the total, I just need to add them up. So if I have two resistors in Siris, I just add resistor. One to resist or two. If resistor one is four OEMs and resistor to is three homes, the total resistance would be seven homes. If I have three resistors in the circuit, I would just add those up. So let's look at an example here I have three resistors. R one is 12 owns our to his 16 homes and are three is a domes. And what would the value of our total? B. Siri's rule number two says that the total circuit resistance is the sum of all the resistance in the circuit, so it's best to write down that statement first, while right R one plus r two plus R three equals or a total. And even though you can do this in your head by writing it down, you'll remember it better. You'll utilize it when you're supposed to, because you'll know what the rule is because you've written it down. We commit things to memory better if we write them down or if we say them out loud versus just looking at them. So then are one. Plus R two plus R three equals our total, and if I put in the values, it would be 12 plus 16 plus eight equals or a total, and then our total is 36 homes, which is the sum of those three values. Now what if they gave me the total of 36 homes and they didn't give me are two is 16 homes ? I could still add up R one and R three and subtract them from the total to get the value of our too. So sometimes when you're given a series circuit math problem, sometimes they give you the three values of the resisters. Sometimes they give you two of them and maybe the total resistance, and sometimes they make it look like you're not getting enough information. But then you'll be able to determine what the current is, or the voltages for one of the other ones that they're not giving you all the information for, and you'll eventually work your way to getting all of the answers, and I'll show you how to do this. When we do our first example, I'll show you how to lay it out on the schematic so that you can easily decide if it's math that I need to do or if it's a rule I need to use. So let's look at another example. What is the total resistance in this picture? If our one is 22 homes and our two is 4.6 homes and are three is 2.8 homes? What would the total B I do? The same exact thing I did in the last example R one plus r two plus R three equals the total resistance. And then I plug in the values 22 plus 4.6 plus 2.8 equals R T and then rt, or the total resistance is equal to 29.4 homes. So it doesn't matter if there's decimal points in the values or if their whole numbers. If you know three of the values, you can add up and get the 4th 1 If it's three loads in the circuit or three resistors, and if you knew the total and you knew R one and R two. You could calculate our three by subtracting the sum of 22 4.6 from the total of 29.4, if that's what the example was that they gave you so serious. Rule Number two is just telling us that the some of the resistance is in the circuit equals the total resistance. And this is a rule for serious, because in parallel circuits the rules will be different. And like I said before, the math will be the same. So let's move on to rule number three.
11. 10 Series Rule 3 Sum of Voltage Drops Equals Source Voltage: Siri circuit rule number three says that the sum of all the voltage drops is equal to the source voltage. So let's look at that on a picture. What this rule is saying is that if I measured how much voltage resistor one was using and I measured how much voltage resistor to was using and I measured how much voltage resistor three was using, then I could determine mathematically what the total voltage Waas. So what this rule is really saying is that e total is equal to e one plus e to plus e three . So if I wanted to find out what the total voltage was of this circuit, if I didn't know when I wanted to calculate it mathematically, if I knew e one e two any three, I could just add them up. That's what Siri's Rule three is telling you. So let's look at this example. It would be e one plus e two plus e three equals e total, and then I would plug in the numbers. In this case, it's four plus four plus four equals e total and then the total voltages 12 volts. Now, in this case, all three resistors air using the same amount of voltage. And there's a reason for that. The reason is, all of the resistors are the same value. So if all the resisters of the same value, they will share the voltage equally. But as we'll see in Rule Number four, when the resistance values air different than even though all of the voltages will add up to the total, the individual voltages for E one e two and E three will no longer be the same. They will be different values, depending on the value of the resistance is so. I'll explain that a little further when we go over Rule number four in the next video and one more point to make. If I took away one of the resisters in this circuit and I still had a 12 volt supply, the some of the voltage drops will still equal to total. But one other thing to note is that all of the voltage always gets used up in a working circuit. So if I have 12 volts at the battery, then all of the resistance is in the circuit will share that 12 volts and all of it will get used up. And if I took away the second resistor and left on Lee are one, then all of the voltage would get used up by the first resistor R one, because all of the voltage gets used up and these air just characteristics of Syria's circuits. And when they designed circuits, they use this information to their advantage so that they can make the voltage drops be what they need them to be. So with only two resistors, it would be e one plus e two equals e total, and then I would plug in six plus six equals e total, and then the total would be 12 volts. So in the next video, we'll look at rule number four, which tells us what's different when we have different value resistors in the circuit. So let's move on to rule number four
12. 11 Series rule 4 Voltages Differ if Resistors are Different Values: Siri circuit rule number four says that the voltage drop across each resistor will differ or be different, depending on the value of the resistor. And this is just saying that each resistor will use a different amount of voltage if the resistor values are different. If the resistor values of the same, they'll share the voltage equally. So let's look at that on a picture if he one is four bolts and e two is two volts and e three is six volts. What can you tell me about the values of the resisters in this circuit? Are they equal values, or do they have to be different? And the answer is they are different. And what can you tell me about which one of these three R one R two or r three. Which one would be the largest resistance value and which one would be the smallest resistance value? And I mentioned this briefly in one of the other videos that they would share it based on the value of the resistance proportionally. So the larger the resistor, it will get more of the voltage if I'm showing that e three is six volts and e to his coup volts and the one is garbled. Then the six volts that E three is showing means that resistor number three is larger compared to resistor number one and resistor number two. And it also means that resistor number two is the smallest and resistor number one is in between the two. Even though these values are different, the rule about them adding up to the total voltage still applies. So I write down E one plus e two plus e three equals e total and then I plug in the numbers so it's four plus two plus six equals e total and then the total is 12 volts, which is what the total voltages. So in this case, it's a 12 volt battery and the voltage is being shared by the three resistors. But it's not being shared equally because the resistor values air different. And I don't have the resistor values labels on the picture, but you know that they're different based on the voltage readings that are being measured here. So if 12 volts is the voltage of the battery, what would happen if I've removed one of the resisters? Let's say I removed resistor number one and left just resistor number two and resistor number three. Would resistors two and three get the same voltage they got before? Would they get Mawr, or would they get less? And would resistor number three still get more than number two or would number to get more ? The battery didn't change, though. The battery is still 12 volts. What's gonna happen is the sum of the two voltage drops is still going to equal the source . So e cu plus e three would still equal 12 because E one is no longer there. And since before E three was measuring mawr than E to, that meant that resistor three is bigger than resistor to it's proportionately gonna use more than resistor to is using. Both numbers are going to get bigger, but Resistor three is going to get most of the voltage and resistor to will still get some of it. In the next video, we're going to do a series circuit example. I'll show you how to lay out the formulas on the page to make it easy to figure out when to do the math and when to use a rule. And after we do one or two of them. You'll see that no matter what the numbers are that they give you, if you lay it out the way I show you, you should be able to handle any problem they could throw at you. So let's move on to the next video and let's give it a try.
13. 12 Series Circuit Example 1: So here's our first Siri's circuit example. Usually what they'll do is they'll draw a schematic, the label, the resisters on the schematic, and then they will give you some pieces of information I've put in in the blue color. The information that they're giving us, they're giving us I t equals 1.75 amps. They're giving this are one is 12 bones are two is four OEMs and our three is eight homes. And then they're asking us to calculate or determine what the values of e one e two e three e Total eye to eye three, our total. And I totally I've found that the best way to attack these problems is to organize your work so that you calculate e i and our for all four locations on that schematic. So you'll have e total I total are total e one I one r one e to a I to r to an IV. Three i three r three. And if you calculate all of the values, then you just have to fill in the answers once you get them on the page. So let me show you what I mean. You can print this out. I've put it in the available resource is so you can print out the example. I'm just going to make it a little bit bigger to give us some room to work. Okay, so now what I've done is I've made four boxes and each one has the three pieces of information that are needed for that area of the circuit. So I hav e Kotal I total are total over here. Then I have for resistor one I have e one I one are one and the same for resisters to and resistor three. And what I've also done is I filled in the light blue information, which is the information that they gave us as part of the example. So they gave us i total they gave us Our one they gave us are too and they gave us are three. The way to attack these problems is to do all of the math that you conduce first and what I mean by math. I mean, homes, law, math and what that means is if I know two things about any area of the circuit, I can calculate the 3rd 1 And if I do all of the math first, and then I can't go any further than I need to use a rule from the Serie Circuit rules that we learn. And I would start at the first rule and just work my way down. And you can even write math or rule up at the top of the page. And I've done that here on this example because what you first want to do is all of the math. In this example. There is no location where I know two pieces of information about any of the different areas. I only know one thing about the total. I only know I total. I only know one thing about resistor one. I only know the resistance value and the same for resisters two and three. I don't know any of the other information, so in this case I cannot do any math. I have to use a rule, and if I bring my Siri's circuit rules over for a second, I can see that the first rule current remains the same is the one I'm going to try to apply . So let's move it out of the way and see if that rule current remains the same or current remains constant everywhere in the circuit. See if that can help me fill in some of the answers. As we learned in the video that explains Siri Circuit Rule One, we stated that if we know any of the current values, the Serie Circuit rule says that we know all of the current values. So what I could do with Rule one here is Aiken. Take the I total current, which is 1.75 AM's, and I can fill that in for I one for I two and for I three. Because Siri, circa rules, says that if you know any of the currents, you know all of the currents. So I've brought the Siri's circuit rules into the bottom of the page here, and I brought our owns law math in case you still need that. And let's fill in. I one I two and I three, and I'm filling them in an orange because we used a rule to determine those values. I'm using a different color, depending on if we did math, if it was the information given from the example, or if we're using a rule and I'm just doing that so that you can see and look back and see how the information was determined. So in this case, the light blue means it's the information that we were given in the example. The orange means we used a rule. And if I write the answer in green, it means we did. Math Rule One has given us three pieces of information here and now. What I do after I've used Rule one, I go back and do all of the math that I can. And now because I know two pieces of information about resistor one resistor to and resistor three, I can do the math to get all of the different voltage values e one e two nd three. So to calculate e one, it's gonna be I won. Times are one and I have both of those values. If I put 1.75 times 12 I get 21 volts and now I could do the same thing for resistor number two. I know that e two is equal to I two times are too. So if I put 1.75 times four, I get seven volts and the same thing for resistor number three. I know two pieces of information. I know that E three is equal to I three times are three, so that would be 1.75 times eight homes, and that would be 14 volts. So now I've used math to get three more answers on this example, and I've colored them as green so that you can see that it was math that was used to determine the answers. We only have two more things to figure out. And if I look in this box over here, I only know one piece of information. So that means I can't do math. It means I have to use a rule. But let's look at Rule number two, since we've already used Rule number one and Rule Number two says the total circuit resistance is the sum of all the resistance. So that means I can take the three resistor values that I know and add them up, and that will give me the total resistance. And that would be 12 homes plus four OEMs plus eight homes. The total resistance would be 24 ohm now that we've used another rule, weaken, do math and calculate the total voltage. So if I use the formula e equals I times are I'll take 1.75 times the 24 homes, and that gives me 42 volts for the total voltage. So now that I have all the answers for all of the voltages, currents and resistance of the circuit, I can go back to my initial worksheet and fill in the ones that they're asking for. So I've brought into the bottom left and bottom, right? The answer is that they were looking for as part of this example. So let's fill them in from the information that we've determined from using the rules and from doing the math, E one is 21 volts. So I write that down. There he three is 14 volts hi to is 1.75 amps. Our total is 24 rooms and then on the bottom, right. We have e two they were asking for, and we determined that was seven volts. He total, we determined, was 42 volts by three is 1.75 amps. We got that from using the rule, and I total is 1.75 amps, so Once you understand what you're doing, it may be a personal preference of yours to do rule before math or math before rule, and either one of them will work out. I'm trying to give you a way of simplifying what you have to think about. So if you start out by doing all of the math first, and then if you can't fill in any math answers, then you use one of the rules. It'll just give you a step by step approach to tackling lease until you get good at them. So in the next video, we'll go through another example. I encourage you to bend some time to try and figure it out on your own, and then we'll go over it in the following video. So let's move on to example Number two.
14. 13 Understanding Voltage Current and Resistance Better: before we move onto the next series circuit. Example. Let's do a quick two minute review of voltage, current and resistance. I want to explain to three terms a different way to enhance your understanding of their meaning. Voltage is the electrical pressure or force that pushes electricity through an electrical circuit. It's measured in volts. We use a volt meter to measure voltage, and it's represented by the Symbol E and some books. If you were doing the math on the circuits, would use the symbol V. Current is the flow of electricity. It's actually the movement of electricity through a circuit where voltage is the pressure. Let's think of voltage as you're looking at the Apple Store, and they just released the new iPhone. Everyone's waiting for the store to open, and there are hundreds of people pressed up against the front door of the store, waiting to go in. That would be people pressure so electricity or electrical has voltage, which is electrical pressure. This would be an example of people pressure, but there is no current flow yet because the store is not open and there's no complete path for them to get inside in order. to have current, we would have to open a door to the store and then we would have people current. The amount of people flowing past a certain point in one second would be how many people are flowing in electricity. It would be measured in amps, and it's a measurement of how much current is passing a point in the circuit in one second . So getting back to our apple store, if we open a small door, we might have one or two people going past a certain point in one second. And if there was more pressure outside the store, like lots and lots of people forcing each other to go through, we might even get three or four people to go through the door in one second, depending on the size of the door. And this is where the third term resistance comes in. Resistance is the opposition to current flow, something that causes a restriction or inhibits current flow. If I have a circuit that has low resistance that will allow higher current flow, and if I have a circuit that has high resistance, that will create a condition where we will have lower current flow resistance is measured in homes and is represented by the symbol are. But to understand it better, let's get back to the apple store. What would happen if they now open to second door or the second of a double door? Now more people could flow inside, so the resistance to getting inside is now less which increase the current flow. And this is the same way it works with electricity. If we have a decrease in resistance, current flow increases and if we haven't increase in resistance than current flow decreases .
15. 14 Series Circuit Example 2: Let's try another Siri Circuit math problem. In this example, there's three resistors, just like the last time. But this time they're giving us E total e one e three and are, too. And that's all the information we're given. And then they're asking us to find six values I t I to R T R one r three and I three. And like I've said before, it's easier to just figure out all of the answers. The three answers for the Totally I and are the three answers for our one, the three Answers for or two and the three Answers for our three and then filled in the information that they're looking for. You can download this problem in the additional resource is and try it on your own. Or you can watch the video as I go through the steps that you might take to solve it. So like we did last time, let's make the schematic bigger so that we can set up the boxes that have the information for EI and are for the four areas of the circuit that we need to calculate. Okay, so I've labeled all the information that they gave us E total, which is 18 volts. E one is 2.5. Holds are two is 10.33 homes and e three is 9.3 volts. And notice once again that I've written on the top of the screen math on the left side and rule on the right side. The color of the text will designate if we used math to calculate that answer, or if we use a rule to determine that answer. So if you're working on this on your own, you can pause the video and then restart up the video whenever you're ready to go over it. Since we don't know two pieces of information in any one section of the circuit, we can't do any man. So we have to use one of the rules. But what's different about this problem if I start with the first rule, current remains constant throughout the circuit. I don't have any of the answers for I so that rules not gonna help me fill in any of the answers, or at least not yet. And then the second rule, where all the resisters add up to the total. I only know one of the resistor values, so I don't have three of them in order to add up to the total. So that moves me down to rule number three. And Rule number three is that the some of the voltage drops will equal the source voltage. And in this case, I have the source total voltage, and I have two of the three other voltages. So I do know that e one plus e two plus e three equals e total. So by adding up E one and E three and subtracting them from me total, I can calculate the value of E two. And when I do that for E to, I get 6.2 volts. Now that I have e two written in Aiken, do math. If I calculate I to using the formula, I equals E over r for the value of I two, I would get 20.6 amps. And since there's nowhere else that I know two pieces of information, I would have to go back to the rules and look over the ones that I haven't used yet. So we'll start again at the top. Current remains constant throughout the circuit, and this time since I now know I to I can fill in the current values for all of the other places. So that means that I total is 0.6 EMS. I want his 0.6 amps and I three is points exams and notice that I've used green text for I , too, because that was calculated by using math. And then I used orange text to fill in the values of I Total I want and I three because we used one of the series circuit rules to determine what those values would be. And it looks like it's time to do math again because I now have two pieces of information for all of the other sections. So I'm going to calculate our total, which is e total over I total. And that gives me 30 homes or one is gonna b e one divided by I one, which gives me 4.17 OEMs and our three is going to be 15.5 homes, which is 9.3 volts divided by points exams and one other thing I want to mention when I'm doing the math calculations around my answers to two decimal places. So if I bring in a calculator when I was figuring out or one it was 2.5 divided by 0.6, and the answer that I got was 4.166666666 etcetera. I found that two decimal places give sufficient accuracy for these examples. So that's why I've put 4.17 here as my answer. I've rounded it to two decimal places and let's clear this. And let's just move this over to this side now and let me show you how the calculation for resistor to came out. If I was to take 6.2 and divide by 0.6, that gives me 10.333333 etcetera. If I'm rounding to two decimal places, I'm just gonna draw a line right here after the second decimal place. And then I looked to the one to the right of my line and because it's a three than my answer would be just 10.33 And once again, I found that using two decimal places works very well for doing all of these calculations. If you use one decimal place, sometimes your answers will be slightly off. If you have to add up the resisters toe, add up to the total or same thing. If you're adding up the voltages and you only used one decimal place, you might be off by a slight amount, and it's very possible to be off by a tiny amount, even using two decimal places. But for all practical purposes, two decimal places is sufficient, so all we have left to do now is fill in the answers that they were looking for. So let me bring those in and let's fill them in. I T was 0.6 amps. Rt is 30 homes. Resistor three is 15.5 homes. And now let's come over here to the other side. I two is 20.6 amps are one is 4.17 homes and I three is 30.6 amps. And one thing that they made tricky about this example is the first thing that we had to do in this example is determine what e twos value waas because all they gave us was Thea other three ease. They didn't give us any of the currents and they only gave us one resistor value and what I found is, sometimes when they're giving you an OEMs law problem, they set it up where, if you're not calculating all of the answers, you might sit there trying to figure out how to get one of the eyes or what to do with the resistor values. And it's the rule that you need to use first. And since they're not asking for E two in the example, some people would not calculate eat to thinking they don't need it. And it's the most important part of this example because it's the calculation that gets you started. And it's the calculation, using the rule that the voltages old add up to the total. So that's one way sometimes that they try and trick you with some of these problems. They won't ask for the thing that you need to find first, figuring that you'll look for ways to calculate the other stuff, and they're really not giving you any other way to calculate the other stuff until you calculate the one that they're not asking for. In the next video. We're gonna learn more about the calculation for power and the power formula, and we'll see that other than making us do a little more math. It's really not that bad, so I'll see you in the next video.
16. 15 Power Formula: we already know the OEMs law formula and how it can be represented Three different ways, depending on if we're trying to calculate e I or are the power formula is very similar and we have another triangle here to help us out. Power is measured in Watts. And if I was trying to find the power, I would use the triangle the same way we used the owns Lord Triangle. I would cover the P and the formula would be i Times E. And if I was trying to find I the current and I knew the power and the voltage I would cover the I and the formula would be I equals p divided by E. And if I was trying to calculate what the voltage waas e then I would cover the e and the formula would be equals p divided by I. So it works the same way as the homes law formula. And just take note that the I in both of those is the same current. So if you knew P and E, you could calculate I or if instead you knew e and are you could calculate I and one other thing to note is just like the voltage in a series circuit. The powers will all add up to the total power. So in the next video, we're gonna take the example we just did before where we were only asked to find e I and are and we're gonna add power to the equation and find out what the values for power would have been. And then we'll practice some separate examples that have us look for power as well. So let's move on to the next video.
17. 16 Series Example 2 with Power: in this video, we're going to revisit Siri's circuit example Number two and we're gonna add the power calculations to all of the answers that we've already determined. In order to add the power calculation, all we have to do is make a little room above the total voltage. So I'm gonna expand the boxes so that I can fit the power calculation inside them. And since this is the first time we're doing this, let's bring in the power Formula triangle and let's bring in the formulas as well so that they're right there on the screen in case we need to have referenced them. And in this example, we're trying to calculate power for all four areas of the circuit. And since we're trying to determine P, the formula we're gonna use is i Times E in all four cases. So if I was to do the math, it would be 0.6 amps times 18 volts for the total power, and that would be 10.8 watts. And then for P one, it would be 10.6 amps, times 2.5 volts, and that gives us 1.5 watts for P two. It's p two equals I two times E to and it would be 20.6 amps. Times 6.2 volts equals 3.72 watts and then for P three, its I three times E three, which is 30.6 times 9.3, and that equals 5.58 watts. So the power formula is no different than the OEMs law formula. Where if you know two pieces of information, you can calculate the 3rd 1 And if we don't know two pieces of information, then we have to use Siri circuit rules if it's a serious circuit that we're doing or parallel circuit rules, if it's a parallel circuit that we're doing.
18. 17 Series Circuit Math Example 3: let's work through some more serious circuit math examples in the next few videos, we're going to look at several different examples, some with the power calculation, some which ist e I and are and we're gonna mix it up a little bit where there is either three resistors to resistors for resisters, just so you can see that it doesn't matter how many loads air in the circuit. You can use the same principles to make the calculations you need and get the correct answers in the additional resource is you can download a Pdf file that has all of the slides. As I walk through the process of solving these math examples, and in the video, I will go over more quickly than before since we know what we're doing now, steps that were taken to get our solution. I encourage you to just print out Page two or Page three and work through the example on your own. And then, if you need assistance, will want to check your answers. Just go further down and I'll walk you through the process. So here's our example. Number three. They're giving us the voltage g two e three r three and our total. And we're being asked to find all of the values of E I and are using OEMs law and Siri's rules. So the first thing to do would be toe make the boxes that have e i n r for each area of the circuit. And if you're doing this on your own, don't forget that you need a separate box for the totals E t i t rt and then a separate box for resistor. One resistor to resistors three. So in this step, all I've done is add those boxes and I've plugged in the given information that was on the prior page. And now when I look at this, I'm seeing that I know two pieces of information for a resistor three. So I'm gonna do the math that I can do. And if I do that, it will give me the calculations for I three and I filled it in here. It would be e three divided by r three, and it comes out to three amps now. The next step would not be math because I don't know two pieces of information in any of the other areas, so that means I need to use a rule. So take out your Siri's rule sheet that we've used before and take a look at the first rule . The first rule is current remains constant, so because I can use that rule, I can fill in all of the other eyes. So we're going to do that all at one time here. So now that I've used a rule, the next step would be to do all of the math that I can, because now I know two pieces of information for the totals and two pieces of information for resistor to. So if I do the math for E Total and for our two will look at the results on this next life . And then once you have these answers because I only have one piece of information for resistor one, it means I have to use a rule again. So if I go back to my Siri's rule sheet, I look at the second rule, which is the sum of the resisters. Add up to the total, and because of that, I know I can add up resistor to and resist or three, which is 24 OEMs and subtracted from the total, which would give me the answer for our one, which is a domes. And then the last step for this example would just be to do the math to calculate the one. And this is how simple it could be. If you just realize that I'm either doing math or using a rule, and you just do it in a step by step process, you look at the examples fill in the information that's given If there's any method you can do, you do that first. And if there's not, then you use a rule. And once you have enough information to do all the math, you can. You do that and then you would use either the rule or math until the problem is solved. And as we go through some of the next ones, you're gonna find that it's just the same process over and over again, no matter what information they give us. If you set it up this way, you'll never be at a loss for what to do next. So let's move on to the next example
19. 18 Series Circuit Math Example 4: Let's take on Siri circuit meth example for this one uses a similar picture to the last time, but the values have changed. In this case, we have e total 12 volts are total 24 OEMs resistor. One is a domes and resistor to is forums. And again, they're asking us to find all of the values of E. I and are using homes, law and serious rules. And just to make mention notice how the three resistors, in example, for an example, three or just in a line across the top, where, when we did example to that also had three resistors. But we had one on the top one on the side and went on the bottom. But they were still all in Siris, so it makes no difference the way they arrange them on the page as long as they're in Siris . This Siri's rules would still apply, so the first step would be to set up the boxes for E I and our and then we plug in all of the information they gave us on the last page and plugged them into the respective boxes where they belong, and the first thing you notice is that you know two pieces of information for the totals. So that means Aiken do math and calculate. I total I total. And here's where you have to be careful. Don't just divide the small number into the big number. I total equals e total divided by our total. And if you need OEMs law to be on the page or if you have it printed out, make sure you glance at it just so you don't get in the habit of just taking a small number and dividing it into a big number. Because in this case it's 12 divided by 24 the answer for I total is 240.5, and I've written it as 0.5 amps. Some people will just right 0.5, and either way would be fine. So now that I have that calculation made, I no longer have two pieces of information anywhere else in the circuit. So that means I have to use a rule, and the first series rule says current remains the same. And because I know the current, that's the total that means for a serie circuit I can fill in i one I two and I three. So that's what I've done here. And now that I've used that rule, I could do more math because I know two pieces of information for resistor one and resistor to. If I make those calculations, e equals I times are for both e one and E two. It gives me four volts for E one and two volts for e two. And that leaves us where we can no longer do math again. So I have to go back to the rules. And this time I'm gonna use the rule for resistance. Rule number two Rule number two says that the some of the three resistors in this case because there's three is going to equal to total 24. So if I add eight plus four, that's 12. And then I can subtract that from the total, which means resistor three will be 12 homes. And, like I've done all along, when I'm using a rule to get an answer, I put it in orange, and when I'm doing math to get an answer, I put the answer in green. This way you can look back and see what we did to get the answer. If you use a color coded system and the blue information is the information that was given from the original example. So now that I know two pieces of information about our three, I can calculate E three and e three equals I three times are three, and it gives me six volts. Now, in these past two examples, we made the math a little bit simpler just so we could work through a couple examples quickly as we move forward. Now we're gonna use the power formula again, and we're going to use more difficult numbers where a calculator would be a benefit tohave . So let's move on to example Number five.
20. 19 Series Circuit Math Example 5: in Syria's example. Five. We're gonna have to resisters, but we're gonna need to calculate the power as well as voltage, current and resistance. So let's take a look. The information that we're given is I total our total and are one. And once again, I remind you that if you want to tackle this problem yourself, stop right here and print out. The additional resource is so you have this picture and then set up the boxes yourself and see how you do. And then you can either continue with the video or look through the pdf that has all of the answer slides and the steps that I took to get to the answer. So here I have the box is set up with power, voltage, current and resistance. And as you can see, I know two pieces of information for the totals so I can do math. So let's calculate e total and P total, and the formula for E total is I. Total times are total. And then once I get that value, I can then calculate the total power by using P equals e times I or I Times E. It's the same thing either way. So the 150 watts, the answer for power comes from 1 20 times 1.25 And just because we've added power here, it doesn't change anything. You still do math when you know two pieces of information. And then now that we are stuck for at least can't do any math, that means we have to use a rule. And the first rule we're gonna look at Rule number one is that current remains the same. And what that allows me to do is fill in all the currents the other values for I want. And I too, because I know I total and some people might ask, Well, couldn't I have done that first and just filled in using the rule first? And the answer is, yes, you could. But when I'm setting it up here in this course, what I'm trying to do is just give you a step by step, where you do all the math you can do first and then use the rule and then go back to the math and then use a rule until you get all of the answers and there would be nothing wrong with using a rule first and then doing the math. I'm just trying to be consistent. So if you're finding that you'd prefer to do a rule first instead of the math and you're coming out with the same answers, then there's no difference. It won't make a difference. So now that I've used that rule for current, it means I can calculate E one and p one. So let's do that now. So 4.6 volts is the answer when I multiply 1.25 amps times 3.68 homes. And then once I get that value, I can then calculate power by multiplying 1.25 amps, times 4.6 volts. And that gives me 5.75 watts and notice because we used math to get those two answers. The P one answer and e one answer are in green. And now that I have that, I have all of the information for the totals and all of the information for resistor one. I need to use another rule because I only know one piece of information for resistor to so The second rule for Serious Circuit says that the total resistance is the sum of all the resistors in the circuit. So in this case, I can subtract 3.68 OEMs from the total of 96 homes, and that would give me the value for our to. And when I do that, I get 92.32 homes. And if you remember back in one of the earlier videos, if an answer has more than two decimal places, we rounded to two decimal places just to keep the math simple because two decimal places is enough accuracy for these examples. And now that I have two pieces of information for resistor to, I can do the remaining math calculations to get E two and P two. So let's do that now. And the answer for voltages, 115.4 volts. And the answer that I got for P two is 144.25 watts. And one thing to make a note of is that the two voltages, the 4.6 and 115.4 they both add up to the total voltage of 120 which is what Siri's rule number three says. We just didn't need to use that in this example. But it's a good way to check your work. If you can get your answers and then say, Hey, the two voltages shouldn't add up to the total Let me make sure I didn't make a math or somewhere else because if they didn't add up to the total and then it means you made a calculation or somewhere and the same thing for power. The P one and the P two should add up to the total power, and in this case, they do. If we add 5.75 watts plus 144.25 watts, it comes out to 150 watts. Let's try a couple more using the power calculation.
21. 20 Series Circuit Math Example 6: Let's try. Example. Six. In this example, we're using three resistors, and the given information is the total power e one, e two and e three. And notice how they're not giving us any of the eyes or any of the resistor values. And for this example, they're only asking us to calculate. I total I three are total R. One, r two and r three and p two and p three. And even though they're only asking us to get just those eight answers, it is still best to make all of the calculations and then just fill in the ones that they're looking for, because when they give you an example that looks like this there intentionally steering you away from calculating some of the answers that you need first before you can get these answers. So the best thing you can do is make. All of the calculations, which we've seen over the last few examples, is very easy, where either doing math or using a rule, and then once we get all of the answers, you just fill in the blanks for the ones that they're asking for. So let's set up the boxes again and fill in the information now. In this example, I don't know two pieces of information in any of the locations, so that means I have to use a rule right off the back. As I look at my Siri's rules, current stays the same throughout the circuit. I cannot fill in any of the eyes because I don't know any of them, so I can't use serious rule number one yet. Syria's role to says the sum of all the resisters equals the total resistance, but they're not giving me any of the resistor values. So that means I can't use Siri's Rule number two either. So let's move down to Siri's rule number three. Siri's Rule number three says the some of the voltage drops equals the total voltage, and in this case, I can use Siri's Rule number three because they've given me the values for E one e two and E three. So if I add all of those up, it gives me E total, which is 237.88 volts. And now, once I have that information, I can now do math. So if I do the math to calculate, I total and our total. I can fill them in right here on the chart. So I total, which was P total divided by E. Total, comes out to 3.8 amps. And then to calculate our total, it would be 237.88 divided by 3.8, and that gives me a resistance total of 62.6 homes. So with all of the math done now, I can go back to the rules, and I go back right to the first rule again that we didn't use earlier and noticed that I can now fill in all of the eyes because I know I total. So let's do that once I have all of the eyes filled in notice that I now have two pieces of information in all of the other three boxes, so I can just do the math to make all of the other calculations. So just keep in mind that to calculate the resistance in each case is e divided by I and to calculate the power it's eat times I. So let's fill in all of the answers. Here's the resistor values 16 homes, 6.6 homes and 40 homes. And now let's do the power calculations, and that gives us 231.4 95.3 and for P 3 577.6 So now all you would have to do is take this answer sheet and go back to the page and fill in the information that they were asking for . And they were trying to be smart by not asking for any of the ease because it was three e total that we needed to do first, and we needed to use a rule to get it. So sometimes they'll give you an example where they don't ask for all of the information. They just asked for some of it. And more often than not, one of the pieces of information they're not asking for is something you need to find before you can get the other answers. So in the next video, we're going to try one more time, and this time we'll use four resistors. And if I use four resistors, that means I'm gonna need five boxes of information, one for each resistor and then one for the totals. So let's give it a try
22. 21 Series Circuit Math Example 7: welcome to a serious circuit. Example. Seven. In this example, we're gonna use four resistors and make all of the calculations for power, voltage, current and resistance. So our first step is gonna be to do whatever math weekend, and I noticed that for resistor one, we have two pieces of information. So let's figure out what the current is for I one and what the resistor value is for our one. And we can't do the resistor value first with the formulas that we're using. So we're going to calculate I won first and then use that answer to calculate are one. There are additional formulas that could be used when you need to calculate our and you only know P and G. But it's really not necessary because you can calculate I first and then do the simpler Matt. But there is a formula for calculating or directly. For example, if I wanted to calculate our and I knew e and P, the formula for our would be e squared divided by p, but to have to deal with squares and square roots for these extra formulas, I've found that it's hardly ever necessary because if you know P and E. You can calculate I and then you could just calculate are using the regular homes law formula of e divided by I just be aware that there are what's called on homes law Wheel of formulas, which adds some additional formulas to make those extra calculations if you wanted to. So let's fill in. I won an R one, and once I have that information, I can now use a rule. And if I go to my Siri's rules, I read that I can use Rule one, which is current, remains constant and because I know I won. Now I can fill in all the other eyes. So let's do that. And I've put all of the other ones in orange because I used a rule to get those answers again. I'm using Green for I one because that answer was obtained by doing man. And now that I've done that, I have two pieces of information in several of the other boxes, so that means we can do more mad. So let's calculate e two and e four and our three and then p two p four and p three. And once I fill in all those answers. Now it's back to using a rule again because in the totals box, I only know one piece of information. So Rule Number two says that all of the resistor values add up to the total. So I now know R one R two R three and r four. And if I add them up, I get an answer of 58.6 homes so I can fill that in using the rule. And now that I have that, I can do the rest of the man. So let's do the calculations for E, total and P Total. So check your answers against mine and see how you did. By now. You should see that you have a process that can handle any type of equation. It doesn't matter if it's two resistors, three resistors, four resistors, Even if it was six resistors, we just have to add more boxes and go through the same process of doing math or a rule until we get all of the solutions
23. 22 Live Video 2 50 ohm resistors in Series: in this video, I want to demonstrate what the voltages and current would be with two resistors in Siris. So what I'm doing here is I have two meters hooked up. I have a volt meter, which is the first meter, and I have the second meter hooked up as an AMP meter to measure the current. And I've created a circuit with two resistors that air 50 OEMs each and I put them in Siris . So the total resistance, you just add up the two resistors. So the total resistance for this circuits gonna be 100 homes and I'm using a power supply that puts out about 12 volts. So if I was to take 12 volts divided by 100 homes, I would get approximately 0.12 amps. What I'm gonna do is right now the and meter is hooked up in series with the circuit. So what I have here is the power supply. Positive is coming to this point right here, and it's going through this resistor and then through the other resistor. And then this lead leads to my am meter, which is this meter over here. And then it goes into the and meter and comes back to the negative terminal of my power supply. And I have my vote meter hooked up where the negative lead is hooked up to the negative terminal of my power supply. And I'm using my positive lead of the Volt meter to make voltage at measurements. So if I put my volt meter here, I would be measuring voltage that's available for the whole circuit. And that's 11.9. And since all of the voltage gets used up in a working circuit, if I measured after the two loads, I would get zero and just noticed that the volt meters showing zero. And when I have to loads that are the same value. Then in Siris, they're going to share the voltage and they'll share it equally. So I'm just gonna move my meter over here now and you'll see that it's approximately six bolts, which is about half the voltage. What I'm gonna do now is switch to 1 50 ohm resistor in series with a 10 ohm resistor, and we'll see what kind of a difference it makes
24. 23 Live Video 10 and 50 ohm resistors: Now I have the 50 ohm resistor, which is this one in series with the 10 ohm resistor, which is this one, and I still have the same power and ground applied, and I still have the and meter hooked up and the Volt meter hooked up the same way as before. Now notice on the and meter that the current is now 0.19 and the reason for that is the total resistance is no longer 100 homes. It's now 60 homes, and if I take 12 volts and divide it by 60 homes, I get approximately 600.2 amps and I'm measuring 0.194 And let's look at the voltage. If I measure the voltage at the power part of the circuit or the positive side of the circuit, I'm getting 11.8. If I measure the voltage after all the loads, I'm getting zero or close to zero. And in between, before, we were measuring six volts. But now, because the two different resistors air different values, they're not going to share equally. So let's see what we have here. So there's only two volts available for the 10 home resistor that means that the 50 ohm resistor used up 10 bowls, and it's only leaving two volts for the 10 home resistor because they share the voltage based on their resistance value. And since the resistance is more, it's using up substantially more of the voltage. Now notice. I have 12 volts. Then I get two volts here, meaning the 50 ohm resistor used up 10 and then at the end of the circuit, I get zero volts, but they're still current flowing in the circuit. It doesn't matter that this reading is zero volt. There's current flowing from the positive terminal of the power supply through the whole circuit, through both resistors and all the way back to the negative terminal of the power supply. Now let's just see what would happen if I reversed the resistors and put the 10 ohm resistor first. And all I have to do is disconnect here, disconnect here, and I'm just going to switch them around. So now this one goes here and positive gets hooked up to this one. Now it doesn't matter which order that they go in. So if I measure appear again, I would get the 12 volts or close to it. 11.7. I'm getting right now, and if I measure down here after both loads, I'm still getting zero. But if I come in the middle, I'm now getting close to 10 bowls. Because the 10 ohm resistor is first, it's still only using two volts. It doesn't matter which one comes first, and it's leaving the 10 volts or approximately 10 volts for the 50 ohm resistor because they're sharing it based on their resistance value, where the higher the resistance, the more voltage that resistor uses up.
25. 24 Live Video Bulbs: in this example, I'm just going to use one bulb in the circuit. So if there's only one load, this bold is going to use up all of the voltage Orosz least that's what we expected to do. If there was something wrong with any of the wires where they had resistance amore than normal or higher resistance than normal, then those wires might use up some of the voltage, and maybe the bulb would be dimmer. But for right now, when it's operating normally, I expect that this bulb would light up full brightness. So let me connect it. So this is the full brightness for this bulb and notice that the current is reading about 0.24 since I know my power supply is approximately 12 volts, I have 11.6 now coming out of the power supply. And if I have a current of 0.2 for one, if I take 11.6 divided by 0.241 I would get approximately 48 homes so that bulb, when it's operating, has a resistance of about 48 homes. So let's see what would happen now if I put two bulbs in Siris I'm gonna disconnect this. And here I have two bulbs, and this time they're much dimmer. We bring them into the picture, notice how the current went down, and the reason the current went down from 0.24 is now. The resistance is higher because two bulbs in Siris the resistance adds up, so there's less current flow. But there's still 12 volts approximately at the beginning of the circuit here at the positive terminal, 12.0, and then, after both of the loads were getting zero and in between the two bulbs, let me see if I can get this lead in there. I'm just gonna connect a pin because I have this connected together where I can get my meter lead in there. So I'm just going to use this pin. And when I touch to in between the two bulbs, notice how, because the bulbs air the same resistance approximately, they're sharing the voltage equally. And what would happen if I added 1/3 bowl? And I'm just going to do this quick, Okay? And notice now that the current went down even further because now I have three resistors in series or three bulbs that have resistance three loads. And at the beginning of the circuit, I still have 12 volts at the end of the circuit. I still have zero volts, and in between, I'm not gonna have six year anymore because they're going to share it equally. So there's eight folds being measured here. That means the first bulb used up four. And then when I come down to this next spot a measuring four bowls, that means that the 1st 1 used up four to bring it to eight. The 2nd 1 used up four to bring it down to four. And then when I come here, I see zero. So that means the third bulb used up the remaining four volts. And just like with the 50 ohm resistors in the last lesson, when you put them in Siris together, they share it equally. In this case, we used to bulbs, and they shared it equally and got six full teach. But when I put three bulbs in Siris, they still share equally, but now they're only getting four volts each. So just keep in mind some of the lessons that should be learned from this. It's great to be able to do the math and get that understanding. But if you put more resistance in Siris, the currents going to go down, and if the loads or the bulbs or resistors or whatever they are, if they're the same value, then they're going to share equally. But if they're different values than the larger resistance is gonna use up more of the voltage.
26. 25 Electrical Prefixes: in this last video, we're just gonna cover the electrical prefixes that sometimes you'll see in OEMs law examples. But most times they leave them out. Where they come into play is if you're measuring something on a meter and the reading you get, maybe is in Millie AM's. If you were going to use OEMs law to calculate voltage or resistance, you would need to make sure that all of your numbers air converted into volts amps and homes so that the math would work. For example, if I was to read on my meter ah, 126 million amps, and I wanted to use that in a calculation for OEMs law, where I knew perhaps the voltage was 12 volts. I couldn't directly use the owns low formula until I converted the millions toe amps and the same thing. If I had a measurement in homes, that was, let's say it was 2400 kilo homes, which means thousands of homes. It's the same is 2,400,000 homes, and it's also the same as 2.4 mega homes, which means 1,000,000. So if you were reading it on a meter, you would more than likely see 2.4 capital M for mega homes. And just keep in mind that you would have to convert it all two volts amps and homes in order to do the math. So what I have here is a chart up at the top, which gives you an easy way to do the conversions. I had the word Mega kilo, None Millie and Micro, and there's a three with a circle in it in between each of those and above it. I'm just showing you the capital M capital, K small M and the micro symbol, because that's what a lot of the meters would show. If you were making that measurement, it would put that little symbol in the window to let you know that you're reading that you're reading on the meter is either mega kilo, Millie or micro. Now the easy way to convert them. I would just be to move the decimal. You're just moving the decimal 0.3 places in each one and let me walk you through one. Let's say on the meter you read 0.158 kilovolts, and you wanted to convert it to volts you would just take kill Oh, which is over here. And in order to get two volts, you would need to move the decimal place three places. And since you're going from kilo to none, which is moving to the right, you would just move the decimal place to the right. So if I took this decimal point right here and I moved in three places to the right, I would be over here at 15.8 volts. So these two numbers the 20.158 kilovolts and 15.8 volts. They mean the same value just as 15,800 million volts is the same value and 15,800,000 micro volts is the same value. So all of these are the same value. Just expressed a different way down the bottom. I have an example where if I knew the voltage was 12 volts and I knew the resistance was 48 kill a homes and notice how there's a K before the OEM symbol, which stands for killer, which means thousands. What I'd have to do before I can use OEMs law is convert the 48 k OEMs into homes and to convert 48 k in tow homes. I would just take the decimal place and move it. Three places to the right. Now on the number 48 The decimal is after the eight. When were writing whole numbers. We normally just don't write the decimal to the right of the eight. So what we're doing is we're just moving the decimal place. Three places to the right and putting in the zeros. Therefore, it so 48 kill OEMs comes out to 48,000 homes, and then we can use homes law to get an answer of 0.25 amps. So the current in this example would be 0.25 amps, which I can then represent in millions to make it easier to read. So the answer would be I equals 0.25 million amps. So I'll make this slide available in the additional resource is so you can print it out and use this tool up top to realize which way to move the decimal place and how many places to move the decimal place over. If you were converting from mega from mega volts two volts. You would need to move three decimal places to get two kilo and three more decimal places to get two volts and the direction that you're going from Mega two volts would be to the right. So you would need to move the decimal place six decimal places to the right. What if you had a reading in Millie and you needed to move to micro, You would move three decimal places to the right. But if you were in Millie and you wanted to represent the number in Kilo, you would have to move six decimal places to the left. So this little chart or cheat cheat as I like to call it, gives you a quick way of recognizing which direction you need to move and by how many decimal places. And what you're really doing is you're just converting one answer into another equivalent answer so that you can use it where you need it. So let me take a minute to say thank you for taking this course, and I hope you've learned an awful lot about Siri's D C circuits and how to handle the math where, no matter what the values are that they give you a long as they give you enough information to solve the problem. You should be able to solve the problem. And if you're having any trouble with it, just drop me a line at Auto Electrical. Edie, you at gmail dot com. And keep an eye out for my parallel D C circuits course and Siri's parallel DC circuits course that are coming out soon. And if you're looking for information on diagnosis and schematic diagnosis for automotive electrical circuits, my top rated basic and intermediate electrical courses are currently available. Thank you very much and have a great day.