SPEAKER 0
right. Good morning, everyone. And good morning to those who are joining us online. It's just me Today. I hope you're going OK with your, um, assessments. I know it's a bit, uh, it's a bit heavy, but then after after this week, you'll have a little bit of a break before the next piece of assessments in this in this unit. Are you going OK? Yeah, that be great. So, um, today the as as usual, there are two components. The first part is just a small part around a particular professional practise element. And it's gonna be short today. And after that, we're gonna talk about, um, the electrical component, uh, in your design and what you need to be able to, um, you know, power. Um, uh, your mechanical aspects or your like, your motors and your gear etcetera. To be able to, um, you know, open your bridge. Uh, so that's what So the electrical component is probably, um, uh the least, uh, involved, I guess, in your in your design. But if you can't, uh, meet your, uh, design requirements, then then it might not support you to get, uh, the higher grades that you you might want to achieve. So let's start with the professional practise, um, component of the unit. So it's around creativity and engineering. So I don't know about you, but often have you heard people describe engineers as possibly boring? Who? Who has Who has heard? OK, where Where do you think? Um, the world would be without engineers. Would you be sitting here today listening to me? Would there be a classroom? Would there be light? Would there be a ability to communicate? Would you have phones, you know, So I don't know why they got that reputation. Probably because they tend to not brag a lot, but without engineering, I put a cartoon here. So this is what you would possibly have. You know, this is the Golden Gate Bridge. This is your place. But you wouldn't even have the material, the textile, the dresses, et cetera. So So I often say we'd still be living in caves without without engineering in the profession of engineering, you know? So it is the the most creative profession that you could have. OK, so, um, it's about assessing what the community needs and then creating something to resolve that and the creative process through design, you know, through first conceiving the CDI principles through the conceiving aspect, then the designing, then the building of it. And then the operating is probably what makes the world that we live in the world that we live in today. It's because of engineering. Um, so I This is where the stage one competency is so so the The creativity applies in two areas. It's basically around conceiving, You know, a world that would, you know, meet the needs of society. But also there is a creativity in problem solving, you know, So engineers generally are tackled with challenges. Some of them are like, you know, very narrow challenges. Some of them are very open challenges, and some of them are just What if the world was this way, how would we tackle it? And in that you need to be able to think creatively about possible solutions to any challenge that you that you have faced. The thinking is just like on your own. Often the thinking is in a group, you know, with colleagues, and often it's multidisciplinary. But the engineers are the ones that are tackling. So there is a great flexibility in thinking and with their technical knowledge, with their ability to think that's how they come up with solutions. Some of them are so like for a small problems, and for them, some of them are for a very large problem. So I'll just show you, um, very quickly, not too long. Just a quick video, if I can. Do you know this guy? I know him. He's a famous rapper. Apparently a few months ago, I was waiting in line

SPEAKER 1
at the food court downstairs in this very building, and I saw someone I had an undergrad class with. She asked what I was doing there, and I said I was here for the career fair upstairs, presenting at a booth for my employer. As it turns out, so was she. But when I said that's what I was doing, she said, What? Why? I thought you were a famous rapper. I said, I am famous, she said. But I thought you were like famous, famous. You're Shalem. You have a job, too. What do you do? So I told her, I'm a civil engineer. I just passed my PE and I design water and sewer systems. She says. You do all that and make music. Wow, you gotta be really smart. And that is the type of thinking that I'm here to challenge today. Most of us are familiar with the concept of left brain people being more mathematical, logical thinking into hard facts and science and right brain people being more artistic, visual and creative. That's actually a myth that's been debunked. But the distinction between the two still exists for a reason. Right? People tend to lean one way or the other, or so it seems. My boss, a seasoned engineer, is quite the poet he uses pretty much every occasion to write a little poem. One of my band mates is a licenced master electrician, and he designs solar power systems for people's houses. So that begs the question. What is the line that can be drawn between these two types of people? What do an engineer and a rapper have in common? The answer can be found by looking at puzzles. When I was a kid, I loved puzzles. According to my mom, I couldn't get enough of them. Sounds like someone who would be an engineer if I had to guess what it is. I like so much about them. It'd be that they're simple to learn, but the challenge is still there, and the ways to come over overcome that challenge are almost infinite. If I gave every one of you in this room the exact same puzzle, you would all put it together differently. But you would end up with the same picture. Now if I gave everyone in this room the same blank puzzle pieces told you to draw on them and then put it together, you would end up with the same result but a different picture. I propose that the problem solving process is like that second example. No matter what you're trying to achieve, you reach your goal using the same materials that are available to everyone else. We're gonna explore that idea with the two things I know best engineering and songwriting.

SPEAKER 0
OK, I'll stop there. You can keep watching it. He he explains how he goes on about designing his rap songs if you're into that. But the interesting thing is really I really liked how he described the problem solving idea. So we all have the same resources, you know, and then how we come up, You know how the depending on the picture that you draw, you know, you can come up with completely different solutions. And I think that's what engineering is that that's that creative process. Does this make sense? Yeah. So you should be proud to be here. So how we achieve this is like in your in your programmes. You know, you all have a design stream where, actually, this is what you're gonna be doing. Like so you have. We feed you the technical knowledge and in your design stream is where you apply the technical knowledge to create whatever product, sometimes multidisciplinary product that has to do with your discipline. And we're starting with this particular unit. So we we feed you some technical knowledge, and then you're gonna go and and design. You know, we we want you to design a particular bridge. But you might have different ways of designing that that bridge. So my my experience. So I So I'm an electrical electronics engineer, and I specialised in what we call signal processing and telecommunications. Um, I grew up with phones like this, not necessarily pink, but with phones like this, you know, if you remember. A couple of weeks ago, I showed you, Like when I showed you the, uh the challenger disaster. Do you remember that? Did you notice the equipment that was there? The type of phones, you know, faxes, et cetera, that you had. Do you Do you not even know what a fax machine is? Yeah. Yeah. OK, so So this is This was my world when I was working as an engineer and we had phones like this. And the biggest invention was in the nineties, and I remember going all the way to New York to purchase my first, you know, Cordless phone. You know, just because it was such such a huge thing, this is This was cool. This is your your you know, first cord like your first mobile phone, actually, like a wireless phone. And when I graduated and I worked as a telecom engineer, we we were working on the, um g s m. Do you know G s M? Yeah. It's the the what we call the second generation of wireless communications. It's when we went to from analogue to digital com. OK, so it was we still had, like, bulky phones like this. And I remember the reason I'm sharing This is I was in a meeting and it was a I was I was, uh, working in France at the time, and we had a a consortium of people from all over, um, all over Europe, and one person from Scandinavia was saying, you know, um, we should we should start thinking of a phone that is also our office. OK, so this thing here but that was, at the time, probably 25 years before this was even, like, came to product. So what? I'm trying to show you here, and at that time, I was like, we're still operating. Our fact is, we barely knew how to do that. And I and I was like, I was just a young graduate engineer. I said, Like, I have no idea what this guy is talking about, like, no idea, you know. But that shows you that the the the thinking that can come up when you work with more senior engineers that have seen things like it opens your mind and you go like who? What? I I don't I can't conceive. And that's the the key word I can't conceive of what he's talking about. But somebody was conceiving of that. And he was an engineer, and he was thinking already. And this is how this came into fruition. Does that make sense? And that's what you will be exploring. This is your next generation Now is, you know, with the open A I we have with all the automation and robotics that we have is is, you know, um uh, you know, see what was coming up. I put here a video. We're not gonna watch it here, but you can watch it here. This is also another, uh, engineer is a professor of engineering and computer science science specialising in machine learning and a I. And he's describing the next 100 years of your life whether they like he's talking to people who are in their forties. But I think he said, if you are in your twenties, just have everything. And, uh but so if you have time to look at it because for me, when I was watching it, it's as mind blowing. And when the guy that I was working with, uh, 30 years ago said like, let's conceive of a phone That's also your office, OK? And that's what engineers do. OK, and that's what you grow to do in in your life. You will shape the world. You know, uh, of the future, the world that the rest of the community, uh, will live in. They might not know that you played a part in it, but that's what you you you will you will shape that world. Any questions on this? OK, all right. So we'll go back now to the technical part of things, and, um so we'll I'll I'll, um, at about just before 10 o'clock, we might have a break, and then, um and then if I don't give you a break, just let me know because I might not have, Um OK, what's electrical engineering? If you look at Wikipedia, it it tells you that it has to do with electricity, electronics and electromagnetism. And if you look at the definition in engineers Australia, it says you can do anything that has to do with the electrical, electronics, communication and computer systems, and that's basically the core of what electrical engineers do. But these activities can apply to multiple things, and actually, at the moment um uh, you know, electrical engineering with all the work that's been that's done in automation. A I, um, and in renewables is probably shaping the the the future of what this world is going to be like. So, um, it has to do with anything that generates basically electricity. So there was a huge focus on for a long time on possibly mining. But there is a strong focus now on renewables, and the governments are really feeding into that like, from solar to water, wind, hydrogen. You know, all sorts of, um, of, uh, sources of electricity that needs then to be distributed, and the distribution of it is not only so. Obviously, there is a lot of work on power lines what we call power engineers. But the power engineering now is becoming a bit blurry because to be able to do this, you need to know communications. You need to be able to send, you know, electricity to the grid. There's a lot of control that takes place. And so the installation, like the the distribution and the installation, also falls within the realm of electrical engineering. So whether it's businesses, um, various sites or domestic installation of, uh, uh of, um, uh, electrical devices. Um, telecommunications. So I showed you, like, that's my what? I, uh, my, uh, work as an engineer. But it's growing like, uh, from, you know, we went from analogue to digital to sales to, um uh, to micro cells to PICO cells. So there is a lot of work around R f and and, uh, distributing of, like, basically being able to, um, send information. You know, uh, data and and and also signals. And there is also this new growing field of internet of things which is at the junction of computer science. So the computer and electrical engineering So it involves, like, you know, the ability to automate everything. So control comes into it the ability to have everything networked and connected. And there is also that communication. And there is also high security aspect to it, from crypto cryptography to network security and all that falls within, uh, electrical engineering with the with the focus on the computer computer science aspect of it. So this is if you have heard the term of it. This is what we call, uh, industry 4.0. I don't know. whether you've heard that or not. Uh, but that's basically network the the connect automation connectivity. And now we're working into, um, going into Internet what we call 5.0. Well, actually, it's not just about machinery. It's about machine machines interacting with here. And and that falls within the realm of what we call collaborative robotics, which is also Cobos. And that's so if you you don't, it doesn't matter if you don't haven't heard this term. But that's basically where the future is like machines and people collaborating and, uh, with a huge networking and automation aspect associated to that. So if you hear the term industry 4.0 industry 5.0, um, Cobos, that falls within the realm of, uh, electrical engineering. Um, there is also an extension from that instrumentation of control everything that has to do, you know, with robotics and artificial intelligence. This is a manned vehicle. All that falls within the realm of electrical engineering. And a few of you are going to do, uh, you know are in the what we call the vertical double that field into the master of robotics and a I, and then you'll be doing a lot of these things, OK, back. So this was just a broad aspect of, uh, what electrical engineers do. Uh, but we start from the basics. OK, so electricity is a bit difficult because we don't see it, you know? So So you you have to be able to One of the things that engineers also have is the ability to abstract things, you know, like if if you can't see it or you can't touch it, you have to be able to abstract it. Even if you see things at some point, you have to abstract things to be able to resolve it at abstract level and then bring it back to building it. So, um uh, and actually, the Ele electrical engineering is probably the field where there is a bit more abstraction than than others. So in your design, so you have a structural subsystem That's your green bridge, Uh, and you need to open it. So this is where the mechanical subsystem comes into it and and you and you do that using motors or one motor or more motors, Uh, depending on your design. And you have to provide, uh, power, electrical power to be able to operate. Um, what we call an actuator. And I think after this lecture, you're gonna start the mechanical lectures, and the lecturer will go more into actuators. But, uh, it's basically something that allows movement, OK? And the motor is going to be able to allow movement for your mechanical subsystem. Um, that's that is basically, uh, opening your structural subsystem, which is your bridge. OK, so far. Yeah, OK, so some of you may have seen in high school uh, some physics. So this is gonna be a reminder some of you might not have done physics. And this is gonna be the first time, um, that you're gonna see some concepts of electrical engineering, So it's, um it's not too happy. So in your project brief, we say that the power that you need to supply, um, so that your your power supply will have a 12 volt basically supply. And can you can have currents up to three. Ms. If that doesn't mean anything to you, it will mean something to you after after this lecture. And then you have Pras to implement these things. So and we say the peak power measurements ignoring initial peaks must be under 10 watts. And you go like what? What does that mean? And then we say that if you want to have a grade mogen pass, you might need to keep this peak power under three watts. So we say in general, you can have it under 10 watts. But if you want, uh, because we're always looking at saving you know things. If you can keep it under three watts, it's an optimal requirement. OK, that's all in your project. Brief. And so let's find out what this means. Uh, in here. So we are doing so in the supply of of control of electrical power. Generally, you have to find the the electrical power that's gonna, uh, create that's going to operate your your motor. So this is normally step one and step two. You want to create, like, control that supply of electrical power. We want to keep things under the three watts, and we want it to ba. Basically, we want things to do what we we want them to do this. Step one. You will do, actually, uh, when you come back from the break through the mechanical lecture, that's you're gonna have two mechanical lectures that will address exactly this step. So for us, we're gonna have Look at what are the motor specifications that you're gonna have? Uh, what is the peak power? And depending on your design, you might want to start looking at some elements of circuit design. OK, so, um, so basics electric, basic electrical engineering one. Oh, one. What we talk about is voltage, current and power. These are the three things that we, you know we always talk about. And then in a circuit, there would be like you can have various components, so those components can be what we call passive or can be active. Passive components are resistors, capacitors and inductor. You might have heard the term. Yeah, And active components are things that do something to your circuit they might amplify. You know, your power, et cetera. They're generally like diodes of amps, you know, and various other elements that have that form part of this. And, um so in this particular class, we'll just have considered one passive component. So that's resistance. And for most of you who are doing a GB 1 20 next semester, you'll be looking at both passive and active components, and then we're going to look at three laws. And if you and these are the three laws that govern all electrical engineering, that it's S law Kiko's voltage law, K v l or Kirk's current law kcl some people say Kirchoff, some people say Kiko so so s Law K v K C. You can analyse and design any circuit you want, whether it's like a small, tiny circuits electronic component or whether it's for power lines, et cetera. It's they are the same principles. So once you understand those, you just have to practise them. They get they're the same laws. The circuits get more complicated, but they are exactly the same laws, and that's what we're gonna be looking at today. OK, so electricity electricity is is basically made of, um, you know, a flow of electrons. Yeah, OK, so far. Yeah, all right. And so, um, an electro like an electron, like, you know, the the measure of of the charge is called the Coon, and the current and A is how many coons like, so is the number. The sorry current is how many of those charges do we have in a second how many flow in a particular second And that's what we define as current. The voltage is an amount of energy is the amount of energy and the amount of charge doesn't mean anything and I'll give you an analogy for that. And, uh, the symbol for VAT is V So these are the people. Actually, this is Mr He was French, I think. I don't know. I think he was Italian And the last one is what? Who was a Scottish engineer? So the pro the power by by definition is current time voltage and we have to look at some examples. And the symbol for power is P and the power is measured in watts. OK, so what you need to remember current OK, flow charge per second volt, like the, uh, the voltage measures in volt and the power is the the is the product of current and voltage. OK, so what's really what's the best way to to describe electricity? Because we don't we can't see it is to often give the analogy of water OK, so if you imagine that you have a pressure pump, you know, and then that pressure pump is like sending water flowing to a particular component that we call a. You know, it could be like a bigger pipe, a smaller pipe. Uh, whatever. So we have something going, some water going through a particular circuit here. So the equivalent of the constant pressure pump is your voltage source here. And that voltage source could be, for example, a battery. Yeah, so that voltage source sends water so current through a particular element. So this element could be a passive component. Like we said, the resistor. So it's like a resistor is like a narrowing of the pipe, or it could be any other component. It could be, uh, an active component. It could be a transistor, a whatever, and these elements we're going to see next semester in a GB 1 20. And depending on what you have here, your current is going to be changing. So this is a bit like what you're gonna have in your circuit design, so you might have a voltage source. OK, um and then it will. This voltage source will send will create will have a particular current. So you have a possibly a motor here that will be drawing some current to be able to operate the bridge open its close, its whatever. OK, any questions so far? OK, so for example and I've just made up some numbers, So first time, I just, uh can I just have a show of hands? Who has heard of this before? Ok. Whoa. Who has never heard of this before? That might be easier. Ok, All right. So for those of you who have seen before, please, uh, I hope that's OK to have a reminder of these things. Yeah, it's It's, uh And to put that in context. So this is your voltage source and we say it supplies 24 volts, OK, And then let's say you've put a motor here and that motor is going to operate. You know, your bridge and the motor takes 100 mili APs. OK, so 100 milli amps is 1000.1 amps. So that's how many charges you have per second. And the question is, what is the power OK for this particular circuit and for this particular circuit. So here we have 24 volts. The current is 100 What is the power? Ok, I'm gonna ask those who has never have who who has never. Sorry. Uh, there was somebody here who has never seen this before. Yeah, I'll put you on the spot. Are you happy about that? No, you're not happy. OK, I won't put you on the spot. So by definition, power is voltage. Times current voltage is 24 volts. Current is 100 million amps. So which is 0.1 amps? The product of those two is 2.54 watts. Ok, so far. So if I have this, if I manage to have a circuit and then the motor but the motor that's operating my bridge is is drawing 2.4 watts. Am I happy with that? Yeah. Why am I happy with that? Because it's it's one of my optimal criterion. And I wanna keep things under the three watts. Yeah, so I'm I'm geared for a six or a seven. Yeah, but suddenly I put a load on the motor, And then when we put a load on the motor and you're gonna do a track on this suddenly draws more, you know, current to be able to operate Does that make sense? if you put something heavier, you're gonna need more current to be able to operate that. What is the power now? Am I still happy? No, sadly, I'm not even within the non optimal component. I'm not. I'm I'm drawing a current. That's below. That's above. You know, the 10 watts maximum. OK, so something is not quite right with this particular design. What can I do? The two things that I can manipulate are current voltage and possibly bring in some other components to control this. And this is what your circuit design is. So if you can keep everything and the and the, you know, the 10 Watts requirements or the three watts optimal requirements, you're all good, depending on what your design is. And that's what your design is going to involve. Does that make sense and you'll and you'll work on that. OK, so let's bring in a component. That's gonna be resistance. OK, so what the resistance does is that it dissipates power. So the voltage across the terminal to the current OK, so the symbol of So, um have you I I don't know whether you've seen this, but have you seen, um, just pure coil like resistance. Things that you can put somewhere and and and then plug them in, and then the water starts boiling. Have you seen those before? Yeah. Who has seen those? But but yeah. Anyway, so it's just like it's just pure resistance. So basically, you have, like, just, uh uh, a device that's just pure resistance. Like from from metal. You can plug it in, and then suddenly it heats the water. So the water, so the So there is a dissipation of heat of power, you know, and that dissipation of power goes through the water and heats up the water. OK, so far so and the resistance is or and that's Mr Or who came up, uh, with with the resistance. Actually, you know, he was He was actually quite, um, prosecuted as an electrical engineer. He he didn't He wasn't always happy. He was, like all his Um uh uh um, all the the sorry. The research that he's had has been all denied has been like, you know, um, and it's almost like before he died that he became recognised for the work he's done. So So this is what the resistance does OK, so you have a bit of a Mr Vault here. The pressure, you know, to push some current through a circuit and the resistance is is opposing that. OK, so that's what's what the, um so one of the most important laws or law. OK, and that's the law that has been contested for a long time before it came to uh and we take that we can take it all for granted if I have a voltage source and I'm gonna talk about conventions a little bit later on how to do things. So I have a voltage source that's supplying, um, some current I and it goes through a resistance and you'll be in your product. You'll be playing with this. You're gonna use different resistance. Resistances. So and we say that I have a resistance of 50 or and if I have a current of 500 mili amps, what is the voltage? So the s law, It says that the voltage is current times resistance. In in 1 20 you're gonna see that voltage is current times. What we call impedance impedance is, um is the equivalent of resistance. But when you have different components whether you have a capacity or inductor or whatever. OK, but in here we say voltage is current times resistance. So we've seen before that power with current times voltage. And now we say voltage is current times resistance Who's familiar with, Um OK, so then you tell me what is the voltage? Very good. So I have So how do I How do I calculate that? So if V is I times R, then I is 0.5 always always go back to, um the, uh, conventional units, which is 0.5 amps. The resistance is 50 s, the voltage is 25 pos. OK, I'm just making up numbers here just to clarify that. But if I have a law is also saying that if v is i times r, then I is the the ratio between voltage and and and resistor and and also, uh, resistor is voltage divided by current. So you can manipulate this, uh, equation the way you want to. So if I have a resistance of one kg or so 1000 and a voltage of 25 volts, then what's what's the current? You can have your calculators, by the way, if you want to. So it's 24 volts divided by one kg. Um, how much is that? It's 0.0 24 amps, which is 24 million amps. 0.0 24. OK, so all these you might choose for your design. OK, if you want to control, you know, the current that you have, Uh you may or you may not. OK, so this relationship between voltage and current So if you were to draw voltage as a function of current, you'd find that you have pretty much a line, and that's the straight line. And the slope of that straight line is the value of the resistor. And that's gonna be what you're gonna be doing in one of your cracks. OK, you're gonna vary the resistance, and you're gonna so sorry you're gonna vary the current, and and for a particular resistance you're gonna find, you know, you're gonna find what's the character characteristic function of this, Um, for this particular surfaces for those who haven't seen this before. Are you OK? Are you OK? Yeah, I think there were some people here also. OK, K V L Cocos Voltage Law. So let's say, And that's that's important for you. Like, because you're gonna have a motor. Let's say you have a 12 volt motor. And, um so your motors generally have a particular They have some specs you can operate them between, Um, you know, let's say if 12 volts, I'm just, uh between say, nine volts and 14 volts. OK, so they they give you some specifications for the operation of that particular motor. Uh, and it depends on the motor that you're gonna be that you you're gonna have. What happens if you have a voltage source? Um, and that voltage source supplies. Um, so a voltage of five volts. What happens to the motor? What does it do? So But it operates around 12 volts plus or minus three volts. For example. What happens if I supply five volts to it? Yeah, very good. It doesn't require the required magnetic field. If you don't understand what that means, you're gonna see that next next semester. But basically, it's not gonna be able to operate. OK, so nothing happens, OK? It's stalling. Yeah, and if I supply, say, 20 volts or 24 volts like motor, what happens to it? what happens? It burns. Yeah, All right. So you have to be careful when you with your design. Depending on the motor that you're gonna be using to open your bridge. That's the The supply of voltage is is right. But it's not gonna be as dramatic as this, But you might have a range of motor, and depending on your supply, you might Yes. Hurt me. Yeah, it's it's powered. Yeah. You won't be like turning a little thing, you know, Um, so if you for this amount of time Oh, you can Actually no, no, you can operate your you can manually press a button. Yeah, you don't have. Yeah, yeah, yeah, yeah, yeah, yeah. No, no, no. You can actually press a switch. But you Yeah, it it still has to be powered somehow. Yeah. Yeah. OK, so it's This is a dramatic scenario, but yeah, So one of the ways we can possibly control that and again, like you might not need any like, all of this. But some of you may need This is you may, for example, add the resistor before or after the motor. So, intuitively speaking, so I have 24 volts here, and my motor operates at 12. Needs optimally 12 walls across that. So I'm putting pressure here to put to have a current going through this particular circuit. And this pressure is some of it is used to put to push the current through the resistor. And the rest of the pressure is used to operate the motor. So intuitively speaking, and we're gonna see that it's one of the laws is that you have You're gonna have some voltage a voltage drop here, V one and then followed by the voltage the the pressure that you need to operate this motor. Does that make sense? Yeah. So if I supply 24 volts and I need 12 volts to operate my motor and I don't want it to burn OK, then what is the the voltage that I need to cross this resistor? I also need 12 volts. Yeah, if I If so, basically what I wanna do is I wanna drop the pressure, you know? So that's I only have 12 volts operating the motor and I need I optimally need to drop the pressure by, you know, another 12 volts. So I want to voltage here about 12 volts. Does that make sense? OK, so if I was to do that, I was gonna ask you a different question afterwards, But so So I I want a voltage of 12 volts. So the question I have is like, could I put the resistor on the other side of the motor? Yes. I can absolutely put the the because I will need still need the same pressure. I could swap the r and the motor. I could have the motor first. I still would have 12 volts across the motor and I have another 12 volts across the resistor here. Whoa! Are you OK? Have I lost you? Who gets that? OK, who doesn't get it? And I'm happy to explain it Different? Who doesn't? Ok, so which bit? The last bit where you can swap the the first bit. You're OK with that? Yeah. OK, so, um uh uh it might be I just thought about it two seconds ago, so it might be a bad analogy. OK, but like please forgive me if I So let's say you have to jump, you know, from, say, two metre heights, OK, and then you have a particular um you have an obstacle that you have to you You can only jump one metre at a time. OK, so let's say the obstacle you want the jump is one metre. Ok? So do I put some staircase before it? Or do I put staircase after it? Which is which is is it possible to do so I I'll put some staircase before that's that's obstacle. So I'll have, like one metre and then I can jump to one metre. You get that? But if I put my obstacle first and then the staircase afterwards Is that OK? I could still do that. Yeah, because either way so whether I have the staircase before or the staircase after, I still I'm only gonna be jumping one metre either way. Is that a bad analogy or does it make sense? No. Only 12 volts go into it. So and then we're gonna So So I have 24 volts here, actually. Let me let me, uh, there's a camera. Why is it uh uh so just a bit of a uh So I'll put the voltage source like this before I answer your question. OK, I have, uh, 26 you can. I can also put you might see the voltage source like this also. Plus is the the positive thing and then that's generally referring to a battery. And this is also generally referring to a battery. OK, just a convention thing. So now I'm I'll I'll get to your thing. OK, so I have a voltage source here of 24 volts. Um, can you see? OK at the back. Ok, so you understand that I want 12 volt here? Yeah, And then to be able to do that to To be able to do that, I'm adding a resistor here. Yeah, and that resistor I'm gonna calculate it is gonna be able to allow for a drop of potential. You know, between this point and this point so that I only have 12 volts here. So now the question is, let's say I have 24 votes and my motor is here, and I still only want 12 volt here. Yeah, I want 12 volts. So if I want 12 volt, I can say Well, all I have to do is create another 12 volts here. If I so only 12 volts. So this whole potential is gonna be is gonna be chunked between the various components that I have in that circuit. OK, so this is basically the K v l law. It says like you're gonna have a particular voltage. So this total voltage is gonna be this voltage Plus this voltage. If I had another component here, then it would have also this voltage here. So basically, it's going to be a sum of voltages across the whole, um, the whole circuit. What? And actually, I haven't put it there, but basically So let's say I have an element here. I have to apologise for my handwriting. It's not the best you know I have. This is the symbol for the earth. This is the voltage. Here is zero volts. Yeah. Zero vote. This is, say, 24 votes, for example. OK, in general. And we put an arrow here like a vector. So this is, uh, c and this is AD. D is linked to the earth. OK, zero volts. So this is I have a different convention. This is V. See, this is the voltage between A and D. Yeah, V AD The voltage between A and D is the voltage between A and B plus the voltage between B and C, plus the voltage between C and D. Like vectors. Yeah, so I can have as many elements as I want and the voltage between those they might not be equal at all, but it's basically whatever voltage that you have between each element. So every time you add something to your circuit, you're having a a voltage drop of some kind. Does that make sense? So now if if this is a B and C, I said the voltage between A and B plus the voltage between B and C is the voltage between a n c. Now, if I swap those elements, it's the the the rule still applies. So let's say now I have I put my motor first and I'm putting the resistor afterwards, OK, the voltage between this point and this point is the voltage between this point and this point, plus the voltage between this point and this point, Yes, So as long as I create a voltage so here of 12 volts, my motor itself is safe at 12 volts. Also, Yes, yeah, yeah. Tell the no, because it's No, it doesn't overheat because because I always have 12 volts across this motor. I'm not. It's not like if you if you put just the motor, it would have 24 volts across it. And then if you put the voltage, you might It might drop. But if I have the two elements straight away, it never. It's never It never has 24 volts against it. And same modules. I was thinking that tomorrow, this week, the motor is not hit with 24 volts. The motor is hit with 12 volts only. Yeah. Yes, OK, Yeah, exactly that. Yeah, because the pressure. So if you the analogy was that the pressure against this element plus the pressure against this element plus the pressure against this element makes up all the you know, the 24 votes? Yes, I'm dealing with K V l I I what you're saying we're gonna cover a bit later. Yeah. Sorry. Can I just So And just to address, address your question, Is the motor hit with 24 volts? Ok, the motor is hit with the difference between the voltage at this point and the voltage at this point, not the voltage at this point and the voltage at this point. So the motor is hit with this particular voltage only. Yeah, it's And this voltage is not 24 volts. So I'm plug, I'm plugging in, and I know it's a difficult concept. OK, so I have, say, a 24 volt battery and I wanna put a motor in here. Yeah, If I connect those two, this here, then I have I am hitting the motor with the whole voltage source here with the whole voltage. Yeah, all right. If I put I have a motor and I have something else in here I hit the motor with this with this. Only who? Who? Yeah, And this The voltage here is not the same as the voltage here. It's whatever it is who gets who doesn't get that. Still, I'm I'm happy to go explain it. Who gets that? OK, do you do you under? Yeah, Well, it's, um uh, This Yeah, Yeah. I don't know how to turn the brightness on on my, uh it seems to be giving me just one. Let's see if I can or maybe yeah. Doesn't seem to be controlling the brightness, Michael. So the lamp? Yeah, there's a lamp that says so. It's either you have this and all the shadows. True life there's there's one lamp thing it seems to be And then the other one is auto tune. And that is a brightness button. You you're welcome to come and have a look if you want, but, uh, please yeah, I think that should be. And the brightness doesn't seem to work. So this is the brightness the It's the same thing here. You can see it from here. You got it? I'll try and control it with the mouse. Yeah, three months that. I think we're gonna let it go. I'm just gonna results, OK? Sure. That's one thing. Thank you. Well done. Thank you. Very good. What happened here in terms of current? Very good. Thank you for that. OK, so in summary, in summary, like so it's not just this point that counts. It's the difference of those two points that counts around. OK, OK, I'm gonna So please have you, Do you? Is that that's important? But did you get that? Ok, All right. OK, ok. So the voltage across this resistor is 12 volts. The voltage across the motor is 12 volts and I can swap them around. And what's important is the difference. What? What? Between the two ports of the motor. Yeah. So if the motor now is drawing 300 million amps, you know, to be able to lift a load or whatever What is the resistance that I need to be able to not burn the motor? What law is that? What low is that? What am I applying? Low. Very good. So I want 12 volts across resistor. I have the motor is drawing 300 milli AMP. How much is the resistance? 40. You found 40. Let's find out. So the voltage is current times Resistor. The resistor is voltage divided by current. And the resistor is 40. Oh, well, very good. Is this clear? So that's how you control. You know, basically your circuit. OK, you can and and as you, uh, advance in electrical engineering, you can control it in various various ways. But so, um yeah, I've I've gone through this now, so I'm not gonna go through it again. You can do it yourself. OK, so Kev's Voltage law says that Please just do this and then we can go and have a break If you are in any circuit the voltage in what we call here a little loop here is that the sum of all the voltages is equal to zero which is basically what I showed before. Like when I said v The voltage between A and D is the voltage between a and B and B and C and DC and D So if you put the algebraic sum, it means that all the voltages in that loop is equal to zero If I go back to so if I apply it in here, it's like this voltage. There are a lot of conventions here, but, um convention. So this is V AD. OK, you've all done vectors before. How do I write this? This is V AD. You ok with this? It's like I'm adding the vector components of the things. I can also write this as v AD minus VA B minus V BC minus V CD is equal to zero. You OK with this? And you OK if I say you OK with this? Ok, this vector here is minus this vector here. Yeah, So this is V B. A. This is V C B and this is V DC. Yeah, So I can write that the sum of the total voltage is the sum of all these voltages. Or I can write it in algebraic sum like this here equivalent following This is K V L in this loop here. This plus this Plus this. Plus this is equal to zero. Yes. Any questions? Yeah. Oh, OK, so this is basically what we've just written V one plus V two plus V three plus V four is equal to zero. That's that's basically voltage the the K V l. And it's one of the very important laws that we need to to remember. So, in any circuit that you have, you have to have a look at where all the loops are. How many loops do I have here in this particular one? Where are the where is the third one? Who says one Who says one live? Who says two Very good. Who says three Ok, where where would the third one be? I don't see what the third one is. This one, this one. OK, so a loop is something that has no no other component in it. So it's just like basically the contour, so you can't have anything. So if I if I have, uh sorry, OK, for example. OK, something like this. OK, so these are just basically wires. OK, so that's you know, uh and we say that the wires have zero resistance. So what you're telling me is that this is also a loop. Yeah. OK, so if I had something in here, would that be a loop for you? Then? It's not. It's basically the uninterrupted thing. It's like, you know, So that's nothing in between. That's what we call a look. So if I had just this how many loops here? What? How many here? Two. How many? Three. Ok, I can add as many, but like it's 123 and then you can apply K V l in each one of them. OK, so in a simple case like this, we've already applied it. We said that this voltage plus this voltage Plus this voltage is equal to zero and then we say that the same current flows through the same components, which is I think, what you said before, like the same water flows through the same components and they all. All the the the same. Water flows through our one and through our two I'm gonna do, um Do you need a break? Yeah, OK, have a break, then. It's so probably the best one for the future on. Yeah, it's really up to you because you can learn the fundamentals. So the electrical major is the broad electrical measure where you learn the fundamentals about everything. If you go to aerospace, you're going to apply those in the context of aerospace, but it's still fine. Transfer into. I have one of my first graduates in, uh, she was in aerospace, and then she went and worked for her first job. So it's not, but so choose whatever you are interested in. What are you interested in? You like that? We going to mechatronics, mechatronics or aerospace? You can do that. Yeah, that's good. And so the aerospace mechatronics, you learn the same principles, except that you have. So there is a stronger systems engineering in the aerospace because of all the safety stuff that takes place. Um, but it's basically a drone Is a drone is a drone. What if, like, the aerospace flows? Yeah, yeah. No, it is question the loops. I think through, um so don't worry if if you, um you'll get used to those circuits, OK? And you'll get used to know, um and and And it's very hard now because I'm abstracting things next week you will be actually Well, not next week, because you'll be on on leave. But the week after, you're gonna be plugging things in a circuit and you'll see that you'll see what I'm talking about. So it's possible that the electrical majors are the ones that require the most abstract thinking and possibly rely the most on mathematics because it's more abstract. Um, so this is my voltage source. I called it the N, I think, and, um, the same current, like water flows through each one of those resistors. I call them R one and R two. The voltage across R one are called V one, and the voltage across R. Two are called V two. And I know that some of you have already seen these things, but it's a, um it's a good way of, uh, applying, um, the laws. So K V. L tells me that this voltage here the in is V one plus V two and I'm all Law tells me that v one How do I write v one? In terms of this resistor R one and current Very good. I R one and V two is the same. Current goes through r two i r two so I can write Sorry, the in here. So the voltage in is the current If I factorise by the current r one plus r two Yeah So this is s law applied to this voltage V one This is s law applied to this Sorry to this voltage v V two, OK, And so I can write this as a particular resistor that I call RSS for series. So which means that I have here an s law that involves a current and a new resistor That's r one plus r two and I can say that this is the same And some of you already know that as replacing two si two resistors in series with just one resistor that I called r s so in your So what I wrote here is basically this. So what? What's the implication of that for your design? That if if, for example you calculate that you need a 40 or resistor like what we have calculated before and you don't have a 40 or resistor. You can choose two resistors in series that are of 20 or each. All one is 13 and the other one is 27 or something like that. OK, so you can make up whatever resistor you have that that you need for your design with or or three resistors as long as the sum of all of them is equal to the resistor that you have. OK, that's what we call an equivalent resistor. OK, so that's an application of K V l Law and s law to resistance in series. Now the next law that kirkoff has is and that's possibly more intuitive If I'm in a node and I have various currents coming to the node, whatever currents come to that node also leave that note. OK, so if I have three on coming three, uh, sorry amps coming and five amps coming. So I have eight amps come into that node. The eight amps have to leave. That node also sorts. OK, so, um Ok, so water coming in water coming out. So for example, in a circuit like this, where I have, you know, a junction here, all the currents that are coming to this particular point. So I one plus I three have have to leave that that particular junction through this resistor IQ. So I have to write that I one plus I three is equal to IQ and same thing at this point here. The other junction is if I two comes in here, then I one leaves this particular junction and I three leaves this particular junction. So either way, um so either way, I two is I one plus I three and that's you may have seen it, but it's called, um k c L. K s current law. So I now have some resistance that are called resistance in parallel. Um so if V in, say, is 24 volts OK, I'm just v. This voltage here is 24 volts. So I'll say that this is connected to the earth. So this is the earth here, and I say this is the end. And let's say this is 24 votes. What's the voltage at that particular point? So this is what's the voltage at this point zero Vote voters at this point, what's the age at this point? This is a wire. What's the voltage at this point? And we assume that there is no resistance in the wire. OK, perfect wires. What's the voltage at this point? 24. What's the voltage at this point? Zero at this 10. This 10. So what's the voltage across this resistance? Uh, one. This is 24. This is zero. What's the voltage across R one If this is 24 votes because they're all the same. So this is basically having something like if you if you were to use a breadboard, which you will, you'd have something that looks this. Is this Yeah. All connected in same point. Yeah. What? The voltage across this one. The same as this voltage. And the voltage across this one is also the same as the the voltage. Yeah. So far, so good. What happens to the current here? It splits. Yeah. According to which law? The one we've just seen K. C. L. We're at at the junction here with a note. Some of it is gonna go into R one, and some of it is gonna go into R two and I'll call the current R one into R one I one and the current into R two. So now in your design, you might consider that this is for the for example, a motor that has an internal resistance A so this current. So if r one was the same as R two, what would you say about the current I one and I two? That'd be the same. OK, because we have the same resistance, you know, same voltage. Everything is the same. So if I was to apply k c l to this, it says that the uh So I is I one plus I two. And if I apply apply s law to this. I is. What's what's Ohm's law across I one What's what's I one is the voltage across r one divided by the resistor But we know that the voltage is the same. So it's V n yeah, or V Whatever I called it. And same thing this one is You OK with this? So this is then v times one on r one plus one on r two. So I'm gonna call this I so I'm gonna replace this. Are you familiar with the sine equivalent here? Well, this is equivalent. OK, so this is equivalent to a single resistor. Uh, and I'm gonna for those two things, it means parallel. And I'm gonna say that's V um this R parallel is this is s law. You with me? This is V. If I replace those two resistors in parallel with a single resistor, I could write s law here. You right with this? If you don't say anything, I'll just won't move on. OK, so if I replace this circuit with I'm gonna replace those two resistor with a single one. Yeah, if I could. And I call this resistor a parallel and I apply or Ms Law, across this, the voltage is the current times. This resistor. Yeah. So I could write that the current here is this voltage divided by this resistor? Yeah, So that's what I wrote here who get who? Who doesn't get that? Who gets this? OK, and there are some that would some of you won't answer. So I can say that the the inverse of the the resistance in parallel is the inverse of r one plus the inverse of R two and you may have seen that for those who have done physics before, that's, um that this resistance. So I I'm gonna call that r parallel is R one plus R two on R one R two and therefore our parallel is R one R two on r one plus r two. These are fractions. OK, so why why is that important is because for the same reason, so I like as before you could have a resistor that you need 40 0 could be replaced by two resistors in series but they could also be replaced by two resistors in parallel, depending on the value that you know that depending on what's more appropriate for your design. So I'm just rewriting this here, OK, so before I move to this one. So if I If I needed a 40 0 resistor yeah, and I wanted to replace that 40 0 resistor with two resistors in parallel and let's say they're of equal value, what would be the value of each resistor that I have to put in parallel? Pardon? A very good. So let's have a look. So I'll have I need I need 40 0 here because that's what we calculated before. Remember for for your motor thing. And I'm gonna say I don't have 40 or so I'm gonna replace that with two resistors that are the same and I don't know what this value is gonna be. It's r so I know that one on 40 is one on R plus one on r So it's two on R. So what's the value of r? So 40 has to be equal to R on two. What's the value of R a t o. So if you have two atoms in parallel, basically your equivalent resistor is half that. If you have two resistors in series that are the same, the equivalent resistor is twice that. OK, so if I have question for you, what's the equivalent resistor? What's the equivalent resistor of this 20? Oh, very good. What's the equivalent resistor of this? So this is the same as 20 of them. What if I had? This was the equivalent resistor of this 18. As as you progress in this, it will become obvious you you become very it will be intuitive. But that's basically how we control things and you go like I had this electronics teacher who used to drive me mad, and he used to say, Oh, well, let's just put this component in there and it will fix everything, and you go, It does. But how? You know, So OK, so a very quick example. This is also K CLI have AC circuit. You have your motor and you want to put you know because it's your bridge and you really want to create some nice lighting, you know, in your bridge, you know, and you're gonna go like, I'm gonna put a little lamp in here, and it has a resistance or R one here, and, um and I know that the motor needs 300 million amps to be able to operate the bridge, for example. OK, And I have a voltage source of 12 volts, for example, a battery. And, um and that lamp needs, you know, um, 1.2 kg kilo on, you know, to to light up. And the question is, what is the total, uh, current I So you're designing your bridge? You have your motor that's gonna draw 300 million amps. You want to put a little light and and what you want to know is like am I still under budget power budget? OK, how do you know whether it is still under the power budget? You know, you have your voltage of 12 volts. What do you need to know? To know if you're under the budget or not? You need to know what the current is. Because if you knew that the current is, then you can calculate your power and then you can see if you still enter three watts or 10 watts or over. So what is the current I? How would you go about it? What do I need to find? So what do I What do I need to? What do I need to find? I k c? L tells me that the total current has split between this lamp. That's I wanna and then the motor that needs to to open the bridge, OK? And so I know that I two is 300 Mili APs. Do I know I one? Not yet. Can I find I one? Yes. How do I find it? Which law? Very good. Low tells me that voltage is current times resisted. Do I know the voltage across our one. How much is it? 12 volts. This voltage. So this is all the same point. This is all wire with no things. So the voltage here is the same as the voltage here. Voltage voltage here. So the motor is fed 12 volts. So it's operating fine. And I can write the 12 volts. The voltage is the current, which I'm looking for times the 1.2 kg Can I find I one. I one is V one, divided by R one and 12, divided by 12.2 kg kilo is 10 millions. So what's the total current? What's the total current? That's that's feeding my circuit? Have this current here split here and it's 10 million amps and it's gone to the to feed the motor So the motor is drawing that and it's 300 million amps. Am I on the budget or not? How do I know? What's the total power? Pardon? Please engage. Was the total power 12 multiplied by 120.31? And how much is that? 3.72 watts. So I if I've added a lamp here, I need 3.72 watts to operate my my bridge. Am I in the budget? Yes. I'm under the 10 watt budget. Am I under the three watt budget? I'm not under the three watt budget. OK, Ok, so this is what I've done before. I'm not gonna go through it again. So this is the equivalent resistor and I we said that we need to have a t o. And, uh, OK, I'm just gonna do one example. And then, um and I'll just give you one little, um, thing at the end. One thing that you might see I'll give you two examples is, um so I'll have this OK, same voltage is what I'm drawing here. The same as what you have on the slide. Yes. So it's the same way I think I can, Um, it's also it's basically one point here and two to resist us here. If you were to put it on your breadboard. OK, so I'm just writing it here because this is how you're gonna often, um, see it. But you're OK that this is the same as this. Yeah, So I'll have, um V one here and V two here and and in some textbooks, you see, it that way. And the idea is to go like, what is the how can I express V two as a function of V one? OK, so, um and the reason why we do that is because sometimes we want to control a circuit by, uh, using resistors to divide the voltage. OK? And we call that a voltage divider. So how it goes. So yes. So you can I use So V is V one plus V two. And if I say it's the same current that going through everything. So this is V two. This is V one, and, uh, I need to do that. OK, maybe I should do it. I can't remember how to do it. So it's R one uh, I plus R two um plus V two. Sorry v is R one plus R two. Oh, sorry V is I times R one plus R two. Are we OK with this? It's almost it's almost law across the whole thing. And it's also, um uh I r one Oh, we're getting stuck here. No, that's all right. So I I one plus v two, I'm going to do it in a very complicated way. which is not the easiest way of doing it. Do that. It's a really bad moment. I have a blank. Uh, what am I doing? Oh, I'm expressing everything as a function of V. Sorry. V is, um I r one plus i r two. And I is, um v on r one plus R two. This is really embarrassing. Sorry about that. Uh, so it's Oh, can I go back to this? I'm just having a blank now, which is really bad. But please don't give me the solution of those that feel even more embarrassed. So, uh, v is blank. I'll come back to it. Sorry, I'll come back to it. So let's start with example two and I'll come back to example one we just shows, OK, you have nothing to OK, so we have a total current of 0.5 MS here we have R one is 10 0 200. Or and the question is like, how I would like to find out three. How do I go about that? So that we have three. I have three laws. Ok, so K v l k c l OS Law. How do I go about finding out three. You tell me. Let's find out what we know. First I know the total current. OK, it goes through this resistor R one. I know the total voltage here. 24 volts. I know the resistor R two, which is 200 on what happens to the current here, is gonna split. I'll just call this I three and this is I two. What do I know about the voltage across R three compared to the voltage across R two? Same. They're connected to the same point. They have the same voltage. Yeah. How would I go about? How would I What are the ways I can find r three? These are the things that you're gonna be doing like all the time, analysing circuits and designing circuits. How do I go about finding R three? What? Can I find voltage across our one? Can I find the voltage across our one? How do I find the voltage across our one? Which law? Almost What's the voltage across our one? So the current going through our one is 0.5 multiplied by 10 arms is how much was the voltage? Five volts. So if I know that this is five volts. What else do I know then? Do I know that this voltage here? Yeah. How much is this voltage then? I have 24 volts altogether. I have five volts across this 19 volts. Very good. So that's 19 volts. So I have five volts across a 1 19 volts across a two. What's what is what? Um does that give me if I know that it's 19 volts? What? What does that give me? So I know the voltage across r two. And what about the voltage across R three? How much is the voltage across our three? Say 19 volts. OK, if I know that the voltage across R two is 19 volts, what can I find? I can find the current across r two. Yeah. How much is the current across R two? I call it R two. So the current across R two or low again is a voltage across r two divided by the resistance R two. So that's we know. It's 19 volts divided by 200 ors. And it's what, nine point five? Yeah, what's how much is that? 95 millions. So if I know that the current across r two is 95 billion amps. Can I find the current across our three? Yes. How very good. Um, is this too fast or you're OK, So I know that this is now 95 Midi amps. I have 500 mili APs coming through 95 Midi amps are going through a two. How much is left? That goes into a three. OK, I think I'm going a bit fast. OK? Do you want me to recap this quickly? Total voltage is 24 volts across our one. We find that it's five volts. Is this OK? Yep. K V l tells me that 24 votes is five plus, whatever is left here, what's left is 19 votes. Yeah, we know that the voltage across R three and R two are the same because they're connected to the same points. So the voltage across R two is 19 volts. The voltage across R three is 19 volts. Therefore, you know, and I know that I know the resistance r two it was 200 s. I'm gonna apply s law and s law tells me that the current so voltage is current times resistor Current is voltage divided by resistor. Yeah, so current r two is voltage. So that's 19 or divided by 200 or and we find 1995 million amps. Yeah, OK, so and I and I know that the current when it comes to this point here is gonna split between r two and r three. That's K K C L. Yeah. So if 95 go here and I have and I have, uh, 500 mils altogether, how much is left across R three. Very good. So the current across R three is 500 mili amps minus 95 which is 405 Medi APS. Yeah. Can I find R three now? Yes. So before I find r three just a question Is r three gonna be larger than R two or smaller than R two? Why is that Smaller is the answer. Who says Smaller? Who says larger? How would you know whether it's smaller or larger? Which one has more current? Our three has more currents. It allows more current. Is there more tightening or less tightening? It's tightening to go through. Does that make sense? So I'm expecting r three to be smaller than R two. So let's find out. And that's the These are the type of questions. When you solve something, ask yourself this question. Does this make sense? Does it not make sense? Yeah. So r three is s law again. The voltage across r three. So which was 19 volts divided by the current, which was 405 MA. Can you tell me what that is? 19 divided by 190.4 oh five, 46.9. Let's say approximately 47 47. Oh OK, smaller than Archie. Then the next question could be find the power dissipated by r three because the power dissipates. How would you go about finding the power across R three Power power is current times Voltage. Do I have the current? Do I have the voltage? Can I find the power? That's what you So then what I could is this is this example Clear Then what I can do is add another resistor. Would you be able to solve this? How would you go about it? It's pretty much the same thing. I've added the resistor, you know, same laws, same three laws apply. You do the same thing you can go back to, you know, And in fact, when you have a circuit design like this, you can you can simplify it and add and complicate it up to it. But exactly the same principle. So, yeah, so you can do that on your own. I just wanna show you something quickly, which you might need in your design, like