Lesson 1 - Voltage, Current, Resistance (Engineering Circuit Analysis)

Hello and welcome to Engineering Circuit Analysis Tutor. I'm very excited to teach this course because I'm also an electrical engineer, so I was always very interested in electricity and electrical

circuit

s and things like that, so what are we going to do? this class is exactly the title, we will learn everything about

circuit

s, we will learn about electricity, we will learn about the components that are part of circuits, but mainly what you do in

engineering

courses is learn to analyze them given a circuit what is happening where it goes the

current

what the purpose of the circuit is and there's a lot of detail there in a lot of techniques that have been developed over the years to achieve those things, you know, a hundred years old circuits and all the things that we take for granted today will be super theoretical but basically they are physical, they are taking energy from a battery or energy from a wall and letting it spin in a loop and doing some useful work with it, that work could be spinning a motor to spin a fan or that work could be shoot a radio wave at everyone to talk to someone else or that job could be going into a microprocessor and, you know, turning on a bunch of bits and adding a bunch of numbers basically creates what we call a computer, but There are basically an infinite number of ways you can create circuits to do what we want them to do, but before you can understand a microchip, before you can understand an amplifier before you can understand a nuclear power plant you have to start. for the basics you have to start with the really very simple questions the things that are so fundamental and that is what we are going to do in this course we are going to start with the fundamentals and then we will continue and talk about circuits and the different types of circuits, how to analyze circuits, find out what happens inside these circuits and you will find that there are a wide range of tools that you will learn in your classes to help you with that now I will say right away that the title of this guy is

engineering

circuit

analysis

, but my goal is try to make it as accessible as possible for anyone who wants to learn it well, don't give up.

The word engineering scares you too much Engineering is a big word that makes it sound very difficult, but I'm going to try to break things down so everyone can understand it now. I will say that the good news is that this is true with circuits in general. There are really no general concepts to understand. In this section we are going to talk about

voltage

,

current

and

resistance

because they are very important, but once you get past that, there are some other general concepts and then you really understand the basic concepts that you face with circuits is that I can draw a circuit in the board and you might know how to analyze it and figure out what's going on and then I can change a little line, a little branch of the circuit. could completely change the way it works properly, so there is an infinite variety in how they can be built, that's what really requires you to have a lot of practice and that's what this course will be, it focuses on practice, practice , practice and, to be honest. with you you don't need to know much more than algebra to do very, very well in this class yes, we are going to use complex numbers a little later later in the course no and no at the beginning we are going to use some calculus and integration later in the course, but in general you can do a lot of circuit

analysis

with just some basic algebra and that's the way I'm going to try to teach it to you so you know everyone who can. be accessible to everyone while also catering to the engineering student, which is really the focus of the class, so I had to figure out where to start.

I think the most important thing for everyone watching this to understand is the concepts of

voltage

and current. and

resistance

because we're going to end up zooming in and talking about those three things for the next many hours and you really have to understand what they are, many students if you haven't already gotten interested in circuits, I get very confused about what the difference is between voltage and current and why resistance influences that. So what we're going to do in this particular section is get closer to that and I want you to really make sure that you internalize and understand what I mean, because as you go and solve a circuit and I ask you what the voltage is, you need to have an inside idea of ​​what that means, even before doing any calculations, so there are no calculations in this section, you know, this is.

I try to make all the definitions as interesting as possible, but it is incredibly important. Make sure you understand this first. I think we all know this. What is an electrical circuit? What is a circuit? I mean a lot of people, a lot of people. I think the circuit is and those people probably do it, but what is a circuit? The simplest definition of a sentence is: it is a closed circuit that carries what do you think it carries? What do you think is electricity? You know, like I say, I have to start somewhere and I start, I start, I never, ever, never assume that you know anything that I'm talking about, so in a circuit you think of a circuit, a race track or a circuit and the Indy 500, it has to go full circle if you don't know. if you do it back to the starting point then you don't have a circuit and no electricity can flow in such situation unless you go back to the starting point, so to have a circuit you have to go back to the starting point, an example simple thing about that without really getting any kind of detail is, you know, here's a source.

I'm going to put a plus minus two different ones to denote it as a source. This could be a battery. You know this could be a battery that you take out that you're going to buy it from the store and we're not going to put anything in the circuit with it, we're just going to draw these lines here, these lines or wires so that It would be like you might think: you get a battery, you connect a wire that comes back to the other side, this completes a circuit, the electricity can go around and around and around here coming from one terminal bottom to the other.

That means it's a super important circuit, but it's also very simple. Now let's go to something that is not so simple, but many people can still understand what current is and when I say current I mean electricity, you know? learn how to spell current, first of all, electric current current, what is electric current, okay, the simplest definition to write what is electric current, is the flow of electrons in a circuit, is the flow of electrons in a circuit, so everyone has heard of it. current electric current an analogy to electric current would be the current in a current, we all know what a current is in a current, right, it is when the current moves, there is a current, it is pushing your boat, right, it is the movement of something, don't confuse that because many people get confused with voltage and current if you are not really familiar with these terms.

Voltage really has nothing to do with anything moving. We'll talk about what voltage is in a minute. The current. The electric current. Think of a current. of something that moves, that's what moves, so in real life, if you have a piece of wire that is metal, the electrons are actually what moves in that wire, so if you wanted to get closer and draw a little picture of that, I could draw another little circuit here, a small simple one anyway, so it goes up, plug it all the way in from the beginning so there's current flowing around and around, but if I zoomed in, let's say this is a chunk cable, right?

I zoom in on this wire and I put a microscope on top of it and I zoom in very, very hard if I could see what I would see inside is a bunch of atoms so this atom will have a positive nucleus and this atom will have a negative electron orbiting around this atom. Now, in real life, this could be, you know, a copper wire, so there will be a lot of protons in the nucleus and a lot of electrons, but for the purpose of this drawing, just pretend that there is a positive Center and there are things negatives orbiting now here is another atom here it has a positive center and it has a negative thing orbiting this one has a positive and a negative each atom has this positive center and negative environment now in metals like copper and gold and silver it conducts electricity well .

These electrons are not actually firmly attached to the atom. They are there, but they can be forced, so to speak, to move. They can be. You know, you can convince them to move if you try hard enough. The object that really convinces them to move is that the battery is better or the source is coming from the wall, for example, and when that happens, when you connect a battery to this wire like this, since these electrons don't actually They are held very tightly. What happens is this electron, you know, down here, this electron is going to jump, literally, it's going to jump, grab it and go into the orbit of the next atom and at that moment, at the same time it's happening, it's a chain reaction. which this guy is going to. the next guy, this electron moves towards this guy and this electron moves towards its adjacent atom and this process happens almost at the speed of light, so you can't see the movement of this electron, but that's what It's actually happening, it's a chain reaction and they're almost like in unison moving from one atom to the next and this movement is really, you know, you can think of it as motion energy, it's the energy that the circuit uses to do what it does.

Whatever you're going to do, you know, turn on a fan, turn on a light bulb on whatever the battery power goes to, push these electrons around which is electric current, so when I draw this here, I'm drawing these negative electrons in motion, so this is what we call electron or electric current. There's another way to say that, so the electrons, if you want to think about it this way, will attract them down here, this is the negative terminal of the battery, this is where the negative charges stack up, so here this is called electrical. current, so the electrons literally come out of this negative terminal, go all the way around and come back and put it back into the positive terminal because the positive terminal is positive, so it will attract the negative electrons and this process goes on and on. and so on until the battery basically runs out, if it's a battery and they can't supply any more electrons or if it's a wall, it just goes on and on forever and they charge you to the right, it comes from the power plant, but the electrons really and really what's moving now let me surprise you a little bit here in a basic course on basic circuits like a hobby book like you know, go to Barnes & Noble or somewhere, just get a book on electricity, they'll talk about electrons. in motion, but when you get engineering and really start trying to analyze how a circuit will actually behave.

It's a little cumbersome to talk about electrons moving, although that's really what's happening and life, the reason it's a little cumbersome is because really one of the reasons why electrons have a negative charge they have a negative charge. negative and what we're going to do later is we're going to have a circuit and we're going to write simple algebra equations, so don't worry too much. but they will be equations and they will describe how the current moves. If we do that for a group of negative electrons, then we will have negative signs in all of our equations for our electrical circuits. and that would totally work, it totally works, however, it's a little bit cumbersome to have negative signs in all of our equations, so in real life as of right now I'm just teaching you this to give you background, but as of right now we're We're not really going to talk about electron current flow or electric current flow.

We're not really going to talk about the direction in which the electrons move. Let me show you what we are going to talk about in this very cable. Maybe you have to do it. Look at this for a moment to realize this, but I think you should be able to convince yourself that since this charge is jumping in this direction for a temporary moment, like we're talking about a chain reaction, this one moves here and this one does it move. here in this one moves here but at the same moment that this negative charge jumps for a fraction of a second this atom has lost an electron, so it is an electrically neutral atom, it has zero charge because the electrons and the protons cancel each other, They're the same number, but as soon as I lose one of these electrons, they're left with some sort of positive charge on the right.

The same thing happens here when I lose this guy for a moment, I have a positive charge here, so these negative charges jump in this direction mathematically. It's the same as pretending I have positive charges jumping from this direction to the opposite direction because this guy has lost an electron and then the guy before him loses one and before him, so when these guys move in this direction, it's the same thing which mathematically means a positive charge. goes in the other direction. I hope it makes sense to you qualitatively.according to my drawing here, but if not, all you really have to remember is that the actual current we talk about in engineering is called hole current and it goes in a direction opposite to that of electric current, which is what It happens in real life.

This is happening and it's a mathematical convenience because now instead of talking about negative electrons moving this way, we talk about positive charges moving this way, now we have positive charges in all of our equations. and all our equations have gotten rid of all these negative signs. or at least a lot of the negative signs are correct and it makes it a lot easier to deal with, so it really saves you time if you think about it that way, saving you a thought process for the actual electrons to go in this direction, but We pretend that we have an equal and opposite number of positive charges going in the same direction, we call it hollow current.

The reason it's called a hole current is because for a fraction of a second, when this electron leaves, it's left as a hole behind this atom that's generating it. that positive guy, then the hole current actually comes out of the positive terminal like this, and we say we denote that current I and electrical engineering or in engineering and is the hole current, this is such an important concept that you really shouldn't continue until you actually You internalize and make sure that basically all you need to remember in the big picture is that whenever you have a circuit, the source will always have a positive terminal and a negative terminal.

Oh, it's like any battery if you take it out of the box you'll see one side labeled positive, one side labeled negative in real life, if you connect the battery to something, electrons, do the objects that go from the negative terminal to the positive, but there is an electrical error in any type of In an engineering course, when you are taking a circuits class, you never talk about the flow of electrons in this direction, this way, you always talk about positive current flow, it is the same value in opposite directions and makes the equations much simpler. and in fact, all the power calculations, the function of the circuit, the energy, everything is completely and totally described by talking about this kind of imaginary current that goes in the opposite direction, so get used to seeing that you are always going to pretend that your currents come from the positive terminal although in reality the electrons are bleeding from the other side now the units of electric current that I talked about, I told you briefly that it denotes current, right, it's probably some history, you can go look above, you would think that the Current would be called C, but it's not called I, so whenever you see, I labeled on a circuit that it's electrical or that's the current that flows through that branch of the circuit or something of that nature.

What are the units? many of you have already heard these units, let's change the colors a little. The units of current are the ampere, which is also called an ampere, or you can just call it an ampere, the higher the number of amperes, you know. the greater the current that goes through the circuit, basically an ampere tells you how many charges are moving through your circuit per second and there is a definition in physics that you can look up for that and that's okay, it's not very important because you really know We are always talking about circuits that you know fit into a physics class, you would be talking about a single charge in motion, there are so many coulombs in a charge that is moving to the right, but in a circuit you have billions of charges in this guy, so don't talk about coulombs and how many coulombs of charge cross through a boundary, you just look at the aggregate, which is how many amperes, which is a coulomb per second, how many coulombs per second actually pass through that guy, so one ampere represents How many coulombs of charge pass through if you cut this wire and see how many pass through there?

That would be how many coulombs of charge pass through there per second, but you don't really have to deal with that too much in a circuit. class, we will always talk about amperes or amps, so let's go back to everyday language that everyone already knows that they have heard of amplifiers, right, everyone has heard of amplifiers, that is the flow of current, the greater the number of amperes in that circuit. is that the more it can potentially kill you, it doesn't take much current to kill a person, believe it or not, you may have a car stereo that has a 10 amp amplifier, that means ten amps of current flows around that. amplifier because to push the sound into those speakers and make them move really loud, you need a lot of physical electricity to get it right and get it to move like that, but in a computer inside a microchip you might have a tiny amount. of current flowing because those are very delicate circuits, you might have a milliamp or a microamp within those types, but the base unit of current will always be the ampere, which is what we have here, to summarize. above, which is really so important.

I keep talking about it. The general current in real life is the flow of electrons. However, in all the circuits from now on that we are going to talk about, we are not even going to talk about this. I'm just going to say that the current comes out of the positive terminal and the unit is ampere, that's really the bottom line now. The next thing we have is the concept of voltage, which many people confuse with current because it is kind of used. interchangeably, the voltage is the push, when I put in quotes, the push that makes the current flow, in other words, it is the source, it is the source, so when you look at a 9 volt battery, that battery has a physical size and it has nine volts.

The nine volt average is a relative indicator to tell you how much, for lack of a better word, that battery can push in a circuit, so current and voltage are very, very closely related, you can't have current flowing without it. something to push it, so you have to have some source there to push it, which is usually a battery or a wall plug or something like that and that's always measured in volts, so when you watch on TV you know, oh boy, could you die with 10,000 volts, well, 10,000 volts. It's not really about how much current flows through you, it's about how much pressure there is, so to boil it down to two simple terms, think of a straw, pretend it's a soda straw, get the restaurant right, and let's say which is quite narrow. straw like almost like a straw that you use to stir your coffee.

Well, if I blow it like this, then I'm going to push air through that straw. The current is the air that is actually moving through the straw. That's what The current is that's what's really making the movement and doing the work. Right now, I'm actually blowing on it, so I'm pushing. I'm actually increasing the pressure at the end of that thing that's causing the current to move, that's the voltage. the push I give it the pressure I give it is what actually makes the current move or in this case the air move through the straw, if I don't blow and I don't give any pressure then there is no current. there is no air flow through the straw, same thing in a circuit, if the voltage is zero, you know, it comes out of the source here, then there is no current, so the two are very related, it's just that the Voltage is the push and current is actually what it is. move, that's really the most important thing you can take away from this guy, so it usually comes from above, where it always comes from a battery or some kind of other source that you can get and that generates on the wall now to the units of voltage that the units have. the volt or just call it V, so that's the same as current, the more volts you have, the higher the voltage, the more potential to move current through a circuit you have, that's why 10,000 volts is so It's much more dangerous than 1 volt, it's not because it measures how much current goes through your body, it's just that if I grab onto a 10,000 volt fence, it has the potential to push a ton of current through my body, whereas a 1 volt source volt is already a lot less than a push so to speak, it's not really going to do much for me so that's really the main difference, the current voltage is tied to the hip, but two different things, the biggest misstep in the one you can get into is Saying boy, that was a really impressive circuit that had 39 thousand volts of electricity flowing through your body.

That phrase doesn't make sense. Voltage does not flow through your body. Just the current. Voltage is what actually pushes current through your body. That's really the main distinction now. Linked to all this, is the concept of resistance very important? Okay, resistance, resistance is very, very simple to understand, it opposes the flow of current in a circuit. This may be a little confusing at first, but think about our soda straw, for a moment. Second, pretend for a second that we don't actually have a soda straw, let's say we have something really big, like a paper towel tube like the one you have.

You buy paper towels at the grocery store and there's a giant cardboard tube in the middle. I hit it. to my mouth and blow, it's pretty easy to blow through a paper towel tube because it's so big, so I can blow all day long as long as my lungs can do it. I can get a lot, a lot, a lot of air out there very easily. I don't have a lot of effort, I really don't have to try that hard to make the air move because it's very large, so we say that the resistance, for lack of a better word like this, to the flow of air is not very large, it has a low level. resistance right now, let's compare and contrast, let's go back to our coffee stirring straw with a very small diameter, so in order for that one to get any kind of air movement through it, I have to blow pretty hard and I can feel it on my lips .

I'm really blowing because we say the resistance of that smaller straw is much greater, the resistance to airflow is greater because it's physically limited, you can't force as much air through that straw very easily. I mean, you can do it, but you have to blow very hard, so we say the resistance is much higher for that type and, in fact, that analogy could also translate directly to two electrical circuits if I literally have a wire, you know, a wire of copper as big as mine, as I am demonstrating. here, let's go big, it has a very, very, very low resistance, the average cross section is so large that tons of electrons can move through it, tons of electricity can move through it without much resistance because it is very large, but if I'm going to find a wire thinner than my hair or maybe I'm going to put a tiny edge of wire on a computer circuit chip that is so small that you have to have a microscope to see them, then the cross section of a tiny wire like That's going to be so small.

It's actually going to resist the current that the electricity is going to move through there, but it's going to cause friction, there's just not that many atoms there for it to move through, so the resistance is going to be greater, so the more The smaller the object, the greater the resistance. will always be greater the larger the object, the resistance will be less, so think of it that way: it is resisting and opposing the flow of current, not because something clever is in charge of it, it's just because of its size generally or because The way it's built, the resistance to the current voltage, they are also intertwined because of the analogy with the soda straw, really the resistance when the resistance is smaller, like the big paper towel tube, then I can move a lot air, a lot of current without much effort. with a lower voltage, and then when I go to a smaller straw, I can still move the current, but it will take more effort, more voltage to get the same amount of current flow or to get the same amount of current flow through that resistance, so the current The voltage resistance is really attached to the hip, it's really interrelated.

Now the units of unit resistance are called ohms, but you never really write home in a circuit, you always use this Omega, this uppercase Omega, and so when you have a 5 ohm resistor it has more resistance than a 5 ohm resistor. 1 ohm, a resistor we'll talk about in the next section, but they actually have a circuit component called a resistor whose job is to resist the flow of current. It seems strange why you would ever need that. Gets to the reasons why you'd need that later, but that little guy is going to try to stop the current flow to assert to a certain point and so the higher the value, the more it's going to try to resist the current flow, just like that the The example that they gave us before, very, very important issues.

Current is the flow of electricity. Voltage is how much push you are pushing to get this current to flow and you are always flowing through something that will always have different size wire resistance. different resistances, different circuit componentsThey will manifest themselves as different values ​​of any number of ohms now for all these types that I have hinted at here, but I will explain it in detail, we can use the metric prefixes for all these types, right? Because these are standard units, we can use metric prefixes, so for example, if you are talking about amperes, which is the flow of current, it may not make sense to talk about amperes, you may have to talk about milliamps. , correct milliamps, like a millimeter, which is one. thousandth of an ampere, or you could talk about micro amperes, ten to the power of minus six amperes, etc., something like this, so the base unit is always amperes, you just have a metric modifier on the front, you might have resistance, do you? how many do you have?

We're talking about the circuit, but it might make more sense to talk about milli ohms if it's a very small resistance or even if it's small micro ohms, that's 10 to the power of minus 6 ohms, or if it's a large value, maybe you have kilo ohms or such. maybe even mega ohms, which is millions of ohms, or here kilo ohms are thousands of them, so the metric system applies here, there's nothing special and for voltage, maybe you have millivolts, you know, maybe you have kilovolts, you know, maybe you have megavolts, maybe a nuclear power plant is running at so many megavolts or something, very, very important concepts, I can't emphasize them enough, so we've talked about current, we've talked about voltage, we've talked about resistance. in detail because it is very important that you understand what that is, it will make my job easier every time we start talking about circuits without you scratching your head what the voltage is again.

I do not remember. I mean, I really need you. To understand that, before we move on to anything else, let's talk about some general things that you probably heard growing up in a general definition, so to speak, that you probably heard first: DC and AC DC versus AC, let's talk about that just for the sake of it. one moment. Secondly, because you know it's something we need to make sure you understand DC, this means direct current, and basically what it means is a constant current flow, basically every battery you've ever used in your life, the triple A ones, the double A and nine volt clock batteries, I mean anything built into a small device that we call a battery, it always generates a direct current, which means that when you connect it to the circuit, it gives you a constant voltage at the location of the source, which pushes the current and because it is a constant voltage, the current output is provided as constant and never changes.

Now actually the battery will drain and get weaker and weaker so the current will eventually fade away but I mean if you take a snapshot and look at it the current is a constant it's called direct current now let me contrast that's with AC, which I know you've heard of and it's called alternating current, alternating current and this means exactly what it sounds like if it's a wall plug and it means that the current, for lack of a better word, is moves back and forth and this is actually a lot easier to understand what the purpose of a drawing is here, so let's draw a quick little circuit like this now that we've normally been putting. plus/minus, but here I'm just going to put a little wave here to tell you that this is an alternating current and we'll get into all of these symbols later, you know in detail.

I'm just trying. to get an idea of ​​what this means and this is a great model of what happens in the wall socket when you plug something, you know, into the wall, what happens is at first the current comes out in this direction and it flows in this direction and then it starts to slow down then it goes back the other way like this and then it goes back the other way and it comes back the other way it literally alternates the direction of the current if you could actually see the tricity coming out of your wall like Yes Could you, if you could, I'm looking at a plug right now there on the wall, if you could visualize a plug, you know, everyone thinks and realizes that electricity is coming out, but if you could see electricity, you would see electricity running. run out and then slow down and then go straight back to the wall and out the other side and then run towards the wall and back the other way and alternate back and forth back and forth back and forth back and forth how many times does it work as well in the United States?

It's 60 times per second. 60 60 Hertz. That is a unit of frequency. That's how quickly it comes and goes. 60 times per second. Electricity is changing direction right now. You could say I should say number one. The question that arises when you explain alternating current and direct current is why do we have a difference? Why do we have a difference? Well, the main reason is that there is actually a lot of history, but the truth is that whenever you generate electricity in a power plant to power houses it is much easier. generate it as alternating current and it's much easier to transmit it to homes as alternating current and that involves a lot of theory that I can't go into right now, but believe me, it's a little bit easier.

I really know all of our power plants, whether they're gas, nuclear, coal or anything else, all they do is generate a lot of heat and that heat usually heats steam and that steam turns on a generator, so all of our plants no matter how sophisticated they are. Even wind farms just turn on a generator, so since they move like that, the current that's generated actually alternates back and forth and comes directly because every time we generate electricity the only way we really know how, except with solar energy. In the panels we do it by rotating a cable within a magnetic field, which is what is inside a generator.

Because of that rotational motion, it's a direct result of how we get alternating current and that's the real reason power plants do that when you build a battery, it's a chemical reaction, it's on or off, there's no motion inside from the battery, so it's just going to give you that constant treatment, the constant current and the constant voltage, so that's the difference between DC and AC in this class. We will focus on DC first, we will learn all the DC circuit analysis techniques because actually when you get to AC, once I show you the method, it is actually not that different, so we will do DC first and it will be really good . and then we're going to introduce the alternating current mechanism, just a couple more definitions.

I want to quickly get to the call of the day. Everyone has heard about this. What is an open circuit? What do you think is good for an open circuit? if you have a correct circuit, if you have a circuit, it's supposed to go back to where it started, if you have an open circuit, it means that somewhere along that path it's broken, basically, so an open circuit would be if I had some kind of source here like here and then I had a breakdown, make this breakdown a little bigger, then there is no more current flow, there can be no current flow in an open circuit by definition, so this opens up here, This is what your wall switch does when you flip the wall switch it simply opens the circuit so electricity can no longer flow.

That's what we call open circuit. Now let's take a moment to talk about a short circuit. Many people have heard of short circuit. Most people know that short circuiting isn't really a short circuit. Good thing, but a lot of people don't know what a short circuit really means when you think about it. If you have a circuit, you have a source and you are supplying power or electricity to some load that we call could here. be a light bulb could be a fan could be anything, so generally for every circuit that's running, we're going to have something here that we're supplying power to to correct this could be anything.

I'm going to put a giant box here, this could be, you know, a fan, for example, right, and this electricity goes out, this current goes into the fan, which makes the fan spin and I'm leaving a lot of details out, but that's basically everything now inside your circuit, let's say somehow a piece of wire accidentally connects from here to here, maybe you're working on a building, let's say you're building the building, you're running a wire through the building and Somehow a stray piece of wire gets connected to two terminals like this or maybe inside your lamp a short circuit develops because the two wires that go to the bulb maybe start touching by accident, what happens is that the electricity comes out this way and when it gets to this junction right here it has the option to go this way through the fan or this way now let me ask you a question what do you think the lowest resistance will be?

Do you think it will be the lowest resistance for electricity? run through this giant fan and waste some or you think there will be less resistance for this electricity to try to pass through this little piece of wire that you put there, it will be much easier for the electricity to pass the wire and therefore electricity will always make it always try to go the path of least resistance, just like you do when you're in traffic, you try to go the path of least resistance, that's why the electricity doesn't even reach the fan, so that's called a short circuit because it kind of truncates the circuit or shortens the circuit and it's very bad for many reasons, but because every time you start getting current going through a wire like this with no resistance or very low resistance, you can actually generate a lot of heat and in fact , you can cause a fire, and that's why you have those circuit breakers outside your house that are there to detect if any short circuit occurs to detect the extra current that increases. current coming from it and turn them off if any type of short occurs in your washer or dryer, maybe some wires start touching each other, the current will start to go up very, very quickly through this little leg and your circuit breaker is in the circuit and detects it and then turns off the circuit, that's basically how it works, that's the only thing I want to talk about in this

lesson

, we've covered a lot of things that we haven't done any calculations, that's okay because you know sometimes in the beginning you really need to Take some time to understand the basics so we learned about the circuit.

You should always have a complete circuit for electricity to flow. We learned about the current. electron flow in real life, but in a circuit analysis we don't talk about that, we talk about positive current and going in the other direction it has an I symbol, okay there in terms of our equations, the unit is amperes o Of course, we can also talk about milliamps, microamps, kiloamps, things like that and then we talk about the voltage that is related. Voltage is the force that pushes the electric current in the circuit. The higher the voltage, the more thrust you have.

The more current you end up getting because you're pushing, you're pushing harder for lack of a better word, the units are a voltage that we talk about or of course you have millivolts, microvolts, etc. then we talk about resistance, which is integral to everything that is kind of the circuit property or cable property, the property of the components and it literally tries to oppose the electric current, the unit is the ohm, which is the Omega capital. Here, of course, you can have milli ohms, micro ohms, kilo ohms with that guy, just like you have with the others, and then we talked about some other random definitions that people have heard over the years of growing up.

DC Direct Current AC Alternating Current This type is usually comes from a battery, some constant current source, usually a chemical reaction gives it a constant voltage, constant current comes out all the time, alternating current comes out of your wall, the reason why the one that alternates is because it's easier to generate because it has rotating generators and having easier transmission to homes there's a lot of theory in that but that's basically the deal and they're both electricity the fact that it alternates doesn't really mean much , I mean, your light bulb, you don't see it. It flashes, but the electricity actually passes through your light bulb back and forth 60 times a second, you don't see it because it's so fast, so don't get hung up or obsessed about the difference, they're both electricity here, both. deliver power and then we talk about open circuit, you have a circuit where you literally take a piece of scissors and cut it, electricity can no longer flow and a short circuit is when you have an operating circuit that you accidentally bridge or connect two pieces together and it basically does that the electricity doesn't even go into the load, so the load stops working, tons of current builds up here and it can actually create smoke and fire if you let it go and that's why we have those circuit breakers in our homes, that's what we want to cover in this section, the title was voltage, current and resistance, it's very important to understand so make sure you watch this until you're pretty comfortable with it in the next few sections.I want to do some For more general information, we'll talk about how to get an overview of the components of the circuit and then we'll do another

lesson

on what we call ohms, which in mathematical terms relates resistance, current, and voltage, and I promise you that Ohm's law is very simple. which you know, you know it blew your mind, it's very, very simple to understand and then once we get those basic things up and running, then we can start to dive into some real circuits and look at how the currents are going to move. through the branches how are they going to add up what is going to be the value of the voltage here the voltage there and then we can get into some more complicated circuit components like capacitors and inductors and much later even what we call transistors and diodes and things like that and, Slowly but surely, over time you will be presented with this beautiful thing.

I think in the 21st century we've called it electrical circuits, so the nice thing about it is that you can learn these things. Can you know it academically? It's good for your career and other things if that's what you plan to do, but you can also go to the store to buy some components once you know what you're doing and you can build a radio if you want, you can build a flashing light if you want you can build an alphanumeric display if you want so it's one of the few things you can actually learn once you understand it you can actually go out and build it if you learn about nuclear power plants they are awesome but you won't be able to build a nuclear power plant if you learn about Einstein's theory of relativity, it's amazing, I love it. those things, but I'm not going to be able to try them myself, but with circuits, once you understand them and learn them, you can play with them and that's what I find so fascinating, so I hope I've sparked your Interest a little bit stay with me , we are going to go through the sections and delve into all of these circuit analysis techniques.

I will try to make them as simple as possible, but you need to practice your problems. Practice the problems we present. here and also the extra problems that are in your textbook