Summary

Voltage, current, and resistance don’t need to be complicated. Learn how Ohm’s Law works and how to apply it to real world wiring problems.

00:00 Hey everyone, welcome to today's webinar.
00:02 I'm Caleb here at High Performance Academy.
00:04 Welcome along and today we're going to be talking about Ohm's Law.
00:08 It's a fundamental part of electrical and what we use on a daily when it comes to performance electrical, motorsport electrical, even just your at-home hobby electrical.
00:18 So, what exactly is Ohm's Law? What does it do? How do we use it? That's what we're going to get into.
00:24 Now, remember this is a live webinar, but it will be recorded, so you can watch at any point in time, but do hang around if you are watching live because we'll have a Q&A afterwards where you can ask me any questions you want and I will answer them in real time.
00:39 Also if you are watching live I do recommend being on a computer if you can.
00:44 I have got a bit of an interactive thing that you can join along with.
00:48 I'm just not sure if it's quite working on iOS or Android, but give it a shot if you want.
00:54 So, let's get stuck into Ohm's Law.
00:57 So, what is it? Ohm's Law is essentially the E equals mc squared to physics, but to electrical.
01:04 It describes and states how voltage resistance and current interact together and are proportionate to each other.
01:12 So, when I talk about that it's one of the things you probably come across quite frequently when you maybe hear about Ohm's Law or read about is a formula which is used to describe this interaction between the three.
01:29 So, I'm going to write this on our whiteboard now you can have a look basically what it is.
01:35 We've got V equals I times R.
01:38 Quite simply it's a very simple formula just basic math.
01:42 We've got V which is our voltage I which is our current or amps.
01:55 Spelling is great we'll just leave all that.
01:59 R is resistance and that's usually expressed as ohms.
02:05 So, how do these three actually play together? One of the things that is a bit easier to look at and you often see is the triangle of Ohm's Law and it's just a bit of a neater way of viewing it as not an actual formula and we just have V, I, R.
02:22 And basically from this formula as long as we have two of these variables whether it be voltage current or resistance whichever two we have we can work out the other one.
02:34 So, if we have our voltage say in our automotive car we have 12 volts and we have the resistance of a say a light globe or some sort of resistor we're able to calculate the current that's going to be flowing through that and vice versa if we need to work out our resistance if we have current we can work that out and also if we need to work out our voltage we use I times R or current times resistance.
02:59 So, very simply that is the core function of this formula, but what some people sort of sometimes have a bit of trouble understanding is how these all work together in a real world situation and why we actually need to worry about this and do this calculation quite a bit.
03:16 So, one of the things you often hear about that I see all the time is expressed in textbooks all that kind of thing is the I guess the the water principle like a pipe and how water and our electrical circuit flow quite similar and they have similar reactions to things like high resistance low resistance.
03:36 I was thinking about it earlier today and I think I came up with a bit of a better live kind of demonstration that can maybe help you think about how these things interact.
03:45 So, first up we've got voltage which is essentially the potential for work to be done by electrons.
03:52 Electrons in our circuit are the tiny little atoms and things that flow around our circuit and move electrical energy around.
04:01 So, when we have a battery that is, it's not creating energy you can't obviously create or destroy energy, but it stores energy and it does that by a chemical reaction and that chemical reaction creates certain negative and positive charges and holes in areas with atoms that allow electrons to move around.
04:22 And some of you have probably heard that the flow of electrons isn't actually positive to negative and in real world it is actually negative to positive and this is true, but for simplicity we all still talk about it in a positive to negative flow just because it's the conventional way it's how it was originally and instead of you know changing all the textbooks and things we just agree to do it that way and all of our functions still work the same, so we can still agree or pretend that these electrons flow from positive to negative.
04:57 So, these electrons flowing in our circuit, they have a state of charge and the amount of charge that they have when it flows past a certain point that is our speed or our current.
05:09 So, current is the amount of charge flowing past a point over a span of time and our resistance.
05:15 Our resistance is pretty easy to think about it is I guess the hose is the probably the simplest way to think about it.
05:23 When you pinch off a hose and add resistance the flow of water going past is restricted and can't flow as well.
05:30 If we get rid of that resistance it's able to flow much better.
05:34 But the one way I was sort of thinking about it was if you grab your hands right, now if you have hands if you don't have two hands I really apologize you can rub any parts of your skin together, do with that what you will.
05:49 So, get your hands and you put them together now when we move back and forth we're using much similar variables that we have in our ohm's law.
05:58 When you put your hands together you can push quite hard or you can simply have your hands resting and be applying little pressure that is your voltage.
06:08 And then the friction of your skin whether you have smooth hands from doing office work all day or rough hands from doing mechanical, electrical hands obviously, are somewhere in between, that is providing resistance against the movement of our hands that is our resistance or ohms.
06:27 Now, current is the speed at which we rub our hands together.
06:33 So, when we change these variables we change things like heat and the amount of energy that's actually, being transferred.
06:41 And with ohm's law it's another sort of it's a separate part, but we can also calculate power or wattage and that's essentially the amount of energy that's being dissipated as a result of our current and voltage or resistance.
06:56 That uses a very similar function and triangle as such and I'll just draw this here quickly just, so we have a reference to it.
07:06 But it is power or our watts over uh i it is iv yeah, so it is power equals current times voltage.
07:18 And, so obviously it's the same deal if we have two of our variables there we can calculate the missing one.
07:24 If we only have resistance and voltage we can use our ohm's law calculator and get our current to then allow calculate power.
07:31 But I'm bringing up power because the the wattage is it's sort of one of the things that we're really worried about when it comes to wiring.
07:38 When when we are calculating the current that is going through a cable that we're trying to size our cable for it's the heat that's being dissipated from that cable that we're sort of we're worrying about that when it comes to our cable sizing.
07:52 Not only that though we are worrying about voltage drop and that is another thing that ohm's law is really good for calculating.
07:59 It is the way we calculate it.
08:01 So, back to my hand rubbing situation here.
08:04 We've got our three variables and one of the things that we can see a result of is our power or heat.
08:10 So, if you push together really hard or if we increase our voltage while keeping the other variables the same we can notice that your hands start to warm up.
08:20 You start getting a larger wattage or power and that is in form of heat.
08:24 In the same way if we were to rub quicker keeping our pressure the same and the resistance of our hands staying the same again we get more heat.
08:33 However, with our resistance it goes in the other way where if we were to lose resistance in our hands maybe you've got some oil on your hands from an engine or lube somehow you're able to go much faster and with less pressure or sorry go much faster, more pressure, but generate less heat.
08:50 So, that's how they all kind of work together.
08:55 So, when we have a generally a set voltage we don't really work with a lot of different voltages when it comes to electrical.
09:03 Yes, we have things like you know 5 volt in computers, 24 volt systems in trucks and things, but kept simply that doesn't vary quite that much.
09:12 A lot of the times the things that are going to vary are our current and our resistance.
09:18 So, when we're sitting around our 12 volt systems and we have say a light globe that has resistance in it, when the resistance of that light globe is more we are restricting the amount of current that can flow.
09:31 So, we're increasing the resistance of our hands, we're trying to keep a steady pressure which is our voltage and the amount of amps or heat that is generated, sorry the amount of amps that is needed to generate a certain amount of heat is determined by how fast we go.
09:49 If we have less resistance in a light globe we have brighter, we generate more heat, but we also use a different amount of wattage, different amount of amps sorry.
10:00 Sorry I'm getting a lot of these mixed up here it's probably making it a bit confusing.
10:05 So, that is where my little calculator display thing here is probably gonna make things a heck of a lot easier and it shows this.
10:12 So, let's actually go over to that and I'm just going to check to see if we've got the link in there.
10:18 I don't think it's in there just yet but one of the guys should chuck a link in there which will take you directly to this calculator.
10:26 So, what I've got here in the screen is my V over I times R at the bottom, sorry it's on the bottom of my whiteboard it's on the screen here, and there's a little bit of a display around it of an actual circuit and we can move some sliders around and actually see how these interact with each other and cause different effects.
10:44 So, just to explain a few things here quickly, we've got on our left which is a symbol here which is showing what our battery would look like, just a green positive negative.
10:54 The right hand side we have a resistor, this can be any kind of resistance it could be a light globe, could be a ECU, it could be a relay coil and it could just be a simple resistor.
11:05 The fact is everything has some sort of resistance, even our wires which is one of the things that is important for calculating our voltage drop.
11:13 But for an example like this we just sort of take into account that it has very little resistance and it's not sort of what we're worried about, we're looking at how the main big parts affect each other.
11:25 So, we obviously have our wires that are joined together and these little blue dots are our electrons, they're representing the electrons moving along and going around our circuit.
11:35 As we mentioned in real world they go the opposite way, but also another thing to kind of think about is they're not moving in a nice straight line like that, they're not going at exactly the same speed.
11:47 In real world electrons are actually bouncing around quite erratically and at different speeds and things, so the terms that we use here they're describing the average or general direction and speed.
11:59 So, when we have a current flow that's the main direction that all those electrons are going.
12:05 Yes, they're bouncing around going every which way, but their general motion is going in one direction.
12:11 And if you think about in another way when those electrons are bouncing around, hitting things, hitting each other, that's when you get things like heat being generated or light or other types of energy.
12:23 They're kinetic energy inside bouncing around, being transferred and turning into a different type of energy, heat or light.
12:31 And when we have something like a resistor what that's doing is it is providing more things for it to bounce around, there's more things to bounce around and hit and things like that.
12:44 So, they generally just go slower through there and that's why we kind of get more heat and or more energy transfer because it's hitting, so much more stuff and transferring that energy.
12:55 And this little calculator here will show that nice and easy.
12:59 So, just down the bottom here I've got my first formula here the V equals I times R and we can click to solve for either voltage, current or resistance.
13:08 And then it's got a couple of sliders down the bottom that we can vary those inputs.
13:14 So, if we have a look here I'm going to do solve for I, so solve for current because that's something we often do.
13:21 We might have a component that we know the resistance of, we know the voltage but we want to know what sort of current it's going to need to run.
13:30 So, I'm just going to slide my bar across here for voltage, I'll just set it to about 12.8.
13:35 Now, if we have a look at our resistance here, if I go all the way to one way we can see my resistor bunches up, has more coils or whatever is causing resistance and it's slowing that flow of electrons.
13:48 If I go the other way, spreads out, less resistance and we can see here our electrons are speeding up and going much much faster.
13:57 And, so we can see here that with our voltage staying the same if our resistance goes down then our current will increase and vice versa if our resistance goes up our current will decrease.
14:10 So, that is sort of the fundamentals of Ohm's law and why it's, so important and how it describes the relationships between all of these things.
14:19 So, how do we actually use this in our real world and why is it important? Well, for something like wiring up an ECU into our car for our engine and everything or a PDM, we always talk about wire lengths, calculating what wire we need to use and a term that is used quite a bit is voltage drop and that's because our wires do have resistance in them and that means that some of our voltage, our potential of energy is going to be lost across that wire.
14:49 And normally in small lengths, decent sized wire, that isn't an issue at all and the resulting voltage drop is, so little that we don't need to worry about it.
15:01 But if we have something that has high current and is traveling a long distance, what we're doing there is we have increased our current and we're actually increasing our resistance as well.
15:13 And if we look, at our calculator, if I solve for voltage we have high current, sorry that's my top bar, which will say around 10 amps and we, I'll start with very low resistance because this, I did this calculator really quickly today, so there are some bugs in it, but at very low resistance, say this is just our wire, we can see that electrons pass nice and freely, but if I increase our resistance it does slow those electrons and we get our voltage here increases.
15:43 Now, in our automotive world our voltage can't just increase like that, so what happens is we have a voltage drop, that voltage is lost along the way.
15:52 And with something like a fuel system this is really detrimental because if we are losing any of that voltage before it even gets to our fuel pump, so it's being lost in maybe a bad connector or our voltage drop across our wire, that fuel pump isn't going to be running at its proper 12 to 14 volts.
16:11 And if our wire is undersized and it's too long we can get really drastic situations where it's running at 9 or 10 volts and this will make our pump run really underwhelming, less pressure, it'll generate more heat and generally we're just gonna have a bad day.
16:29 So, touching on that as well, as I said a wire has its own resistance.
16:34 When you increase the size of a wire we are essentially lowering that resistance, there's more room for things to flow through, you've got more, there's more room for those electrons to flow and it's easier for them, so we less of that voltage drop and we also get less heat.
16:51 So, that is why when it comes to sizing wire voltage drop is really important because if our voltage is dropping before it even gets to our component it's not good and we also by decreasing the amount of voltage that's there we do generate more heat in some situations.
17:08 More heat also reduces the, sorry, more heat increases the resistance of a wire which as we've seen here increasing the resistance is going to cause issues in itself.
17:18 Another thing we're going to touch on here is the power.
17:21 So, this is also important for us, I know I've sort of left it to the side, but when it comes to calculating something like a light bulb it shows here as well how important that is.
17:33 A lot of the time when we have a light bulb, say we're sizing up our wire or a PDM output, something like that, we're often given a wattage on our light bulb and the voltage rating.
17:44 So, we know our voltage and our power and we can use this separate calculation.
17:49 As I said we can use our Ohm's law to get our power and current, sorry our voltage and current from that resistance as well, but it's easier when we have a little calculator like this.
18:00 Now, if I solve for our current that's something we often do, we're trying to work out the actual current that's going to be flowing through, the speed of our electrons and we'll have say a 14.8 volt system and a headlight globe, say a high powered high, high low, high headlight bulb, they're generally around the 100 watt range.
18:27 So, if I set our calculator to that we'll see we've got about 6.86 amps and our light bulb is fairly bright.
18:38 Now, if I reduce that down to a 21 watt which we'd find in say a taillight park light globe, we get more resistance and that is then slowing our electrons which then results in less power, less light, less heat.
18:53 There's a little kind of calculator here for temporize, now that's a bit hard to really calculate when it comes to this kind of thing because it's very dependent on our cable and the insulation, it's based on how quickly that cable can dissipate our heat and it also depends on our ambient temperature, things like that.
19:13 So, I've just got a few little different things you can select here to kind of give you a bit of an idea, but say just a single wire free to air, if you're pushing 1.42 amps through just a single wire we're going to get a 210 degree increase in heat.
19:35 If I go to say a large resistor in free air, that's probably more of a light bulb kind of situation, we can see that a 21 watt bulb would in this situation, this wouldn't be real world obviously because we have different scenarios, but just for an example 63 degrees that's above ambient, so it adds on to our ambient temperature.
19:56 If we go back to our 100 watt bulb we can see that that temperature drastically increases up to 300 degrees and if you ever touched a light bulb when it is on we know that they get pretty dang hot and we can burn ourselves quite easily and that is because of this relationship between all of our current resistance and our voltage.
20:17 In this situation we are reducing the resistance of our light bulb and that's allowing those electrons to flow much faster and with your hand situation if you start moving your hands a lot quicker you generate more heat in your hands, so that's how that is sort of referenced there.
20:35 Now, what else, I think that pretty well covers most of that, I'm just trying to think if there's anything else that might be sort of detrimental here.
20:44 Make sure if you guys are in the chat definitely give me some questions, this is a fairly short thing to talk about, I just want to go over the important parts.
20:56 We will have this calculator up on the website permanently at some point, it's definitely easy to visualize and see how things work together.
21:05 You can also notice I've got those little heat lines on the resistor, they just give you a bit of an idea of if I go back to my I over R, set voltage and changing our resistance, the less resistance we have and the faster those electrons are moving through, we get a lot more heat and power coming out of that wire or the component, light, whatever is transferring energy.
21:30 And vice versa if I go all the other way back, now there's a bit of fine tuning here, the more resistance, the more those electrons have to work to get through, the electrons are moving through quite a bit slower, there's less heat because they're going through slowly and not doing a hell of a lot.
21:51 And we can see that because the light bulb is quite dim.
21:55 Solving for resistance, often we can use that to diagnose some issues in our cars, so, you might know the set resistance or current of a circuit, so let's go with you know the current of a circuit, so you know how much something should be drawing, you know the voltage that it should be drawing that at, 12 to 14 volts, with that information we can get a pretty good idea of what the resistance of that component should be.
22:28 And if we go back to our light bulb example, let's just say what's our 60 watt bulb, this is saying the resistance would be, where is resistance, does it have it on here? I don't think I do.
22:45 That's all right, the voltage we've got 14.8 and 4 amp, so I can put those two in, solve for resistance, that's what sits there, and that tells me that R is 3.7 ohms.
22:54 Okay, so, we know that our light bulb should be 3.7 ohms.
22:58 Now, with a light bulb it's pretty easy to say you know if the light bulb doesn't work, we can see if that's the problem, but if we're testing something else we can use that amp, the known amps and our known voltage, we now know what resistance that light bulb should be, we can go and check that with a multimeter, if it's drastically higher or there's much much lower resistance, we know that there is an issue with that light bulb.
23:24 In a light bulb situation where the filament is actually blown, we will see infinite resistance or infinite ohms, that's because we have more than we can actually measure there, we're actually measuring the air gap between that filament, and air itself has resistance and that's why we can't pass electricity just through air as it is with DC low voltage, because there's, so much resistance in our air that it can't get across, that's why if we increase our voltage a lot to you know in the tens of thousands we can actually jump that gap and you see sparks like in our spark plug, and that's because we've increased our voltage to a point where it can actually, pass through that resistance.
24:09 I think I'm getting pretty close to explaining as much as I wanted, as I said this would be a pretty short one, but I would really appreciate if you guys got any questions, so I can you know elaborate on a few things.
24:23 I'll jump into the, I'll check the questions in a second, just really want to think about whether I've, I feel like I've glossed over something way too quickly.
24:33 Just going over an explanation of the the symbols here, you see if I increase the voltage there's extra lines, generally that's because in a, I've done it that way because batteries will have cells of you know the lead and things and electrolyte and things like that that make up your battery.
24:52 Generally, the more voltage you have from a battery it is more cells when you have you know, that's why if you put two batteries together in parallel you're essentially adding all those cells together or in series you're putting them in a straight line or in series with each other and we add to the voltage.
25:11 So, that's kind of just what is explained there is extra cells.
25:15 I talked about already with the resistor your increase in resistance and it's sort of showing that by adding more zigzags to it, more resistance lines and increasing the heat and you can see the electrons moving faster.
25:29 Let's see if we got any questions while I am running out of things to talk about.
25:34 Got a couple here, awesome I was worried that I was going to just cut things way too short.
25:40 Jerry3567, I'm looking for the correct wire sizing for 1.21 gigawatts at 12 volt, any recommendations? 1.21 gigawatts? What are you doing that's 1.21 gigawatts? That's quite a bit.
26:01 So, just touching on this as well I am working, we've got some tools on our website, I'm working on a wire calculation calculator and interactive thing as well which will be a lot easier for this kind of thing.
26:15 It's very hard to give a correct wire sizing just from limited information.
26:21 One of the things I'm trying to sort of get into here, like I said voltage drop is a huge thing, we really need to know a lot of things like what type of wire you're using because higher quality wire such as tefzel versus a pvc coated wire, that wire's ability to dissipate heat through that insulation is a key factor in what its current rating is.
26:45 So, if a wire is able to dissipate heat safely, it can handle holding more heat in its insulation, that generally gives it a higher current rating because we can pass more current through, we can rub our hands together quicker and generate more heat, but we can do it safely and we can dissipate it safely.
27:05 I think we're getting some add-on to that question maybe, hopefully? Just also, oh here we go, just 1.21 gigawatts required by the flux capacitor in the delorean time machine to travel through time and back to the future.
27:22 Okay, that makes more sense, that's probably why it's a ridiculous amount of watts.
27:29 Well, let's, how many is giga even for watts? So, i'm just going to continue on this, Jayden can you look up just what 1.21 gigawatts is in watts? I'm curious how many, I can't remember off the top of my head how many zeros that is.
27:43 Anyway what was I saying? So, yeah when it comes to actually calculating wire size we really do need to take into account quite a few things.
27:50 I think it's a bit, that's one of the things that I get a bit frustrated, but just is a bit of a worry.
27:57 There's diagrams and charts that show rated amps for a wire.
28:01 People often look, at those ratings and go okay that's the max amp, so I can run through that and they'll just go ahead and do it regardless of every other sort of variable.
28:12 And that becomes a problem if you're as I said long wires with high resistance from that long stretch of extra copper.
28:20 Also if you're running that wire in an engine bay where there's high heat that will then impact how much heat can actually, be dissipated.
28:29 So, all these things come into account when calculating how much amps is going to be bad for your wire.
28:35 And you'll find those charts actually do state somewhere what scenario environment those amp ratings were calculated at.
28:43 So, it might say you know 60 degrees above ambient or say 60 degrees with a heat rise of something something ambient temperature.
28:52 And then it will say a length of wire and things like that.
28:56 They're all things we need to take into consideration.
28:59 It's sort of there as a basic understanding of what wire is better for what.
29:04 So, when it does come to measuring your voltage drop you do need to know the resistance of your wire.
29:10 As I said we need two things here we've already got our voltage and we've got our no, we're calculating our voltage sorry.
29:18 So, we've got our current that we're going to be passing through.
29:20 We need our resistance of our wire to know how much voltage is going to be dropped.
29:24 For our resistance we can look up the data sheets for our wire.
29:28 Most wire companies should have that somewhere and it will tell you generally a per foot resistance in ohms and you can use that in your calculation.
29:37 If we put our calculation of current if we say we've got five amps give that with our resistance that will give us straight up a voltage and that is our voltage drop.
29:47 Cool, so we got here one one ah, so that's one billion two hundred and ten million watts.
29:56 Okay, so divide that okay, so to actually do this it's p equals i times v.
30:03 We need what have you got you had 12 volt yeah, so it is 12 1 billion it's that divided by 12 essentially and that'll give you the current.
30:16 So, let I'm just going to bring my calculator and quickly do that.
30:24 I've got here we've got one two one zero zero zero zero zero zero divided by 12.
30:31 So, that is going to that amount of power with our voltage is going to give 100 million well about 101 million amps.
30:42 I don't think we've got any wire that will take that at least not off the top of my head.
30:49 I don't yeah it doesn't yeah I missed the back to the future reference.
30:55 I'm sorry yeah my mind is on other things right now, but I appreciate that one.
31:01 Hopefully, they don't like it yeah that was a you know a non-realistic scenario of watts, but the fundamental is exactly the same.
31:09 Obviously, with our light globes for a car we're looking at 100 watts as opposed to a billion.
31:15 So the the calculation's still exactly the same and you know by that we can see we we're probably not be able to run a flux capacitor with today's wiring and yeah I don't know if you didn't get a fuse that would last that big.
31:28 I guess that's why things were blowing up, so much and you know things caught on fire.
31:33 What else have I got here? Next question I've got is CL audio tuning.
31:39 Would this webinar go into wire gauges versus length versus current demand? So, yeah I think I've touched a little bit on it, but I do I did have another webinar yeah I've got another webinar that goes a bit deeper into actual wire calculations and determining what wire size you want which I go more into detail on you know why these things play a factor in our wire size, so I do recommend going and checking that one out.
32:07 Links versus current demand.
32:09 So, that's yeah it's probably one thing I want to touch on though is how do I explain it? A lot of people I see talking about you know wire size and that kind of thing and they often say that I hear people saying things like you know you don't push that many amps through or they're sort of talking about it as if we have control how over how many amps are going through.
32:33 Now, we do have control by adding resistance but in a real world when we're wiring something up we have our set voltage and we have our set resistance of components and when those things are set there is only going to be a certain amperage it's not going to we can't change that unless we increase or decrease our voltage or add more resistance or take resistance away from our circuit.
32:59 And we can see that quite obviously here if we if we go to my solve for current we're going to have a voltage of 14.5 and yeah whatever resistance I put in there, so whatever resistance of the component is our current is determined by that and it is as I said at the beginning fundamentally they are linked together essentially and they will react together.
33:25 You can't just say at 14.5 volts with a component that has 3.4 resistance I want you know 20 amps going through it.
33:34 When we do things like that we need to add resistance or take resistance away from the circuit.
33:41 That plays into LEDs we do often see when you are fitting LEDs to something because their voltage that they run at is quite low we need to limit the amount of electrons passing through per second, so we need to limit that current.
33:58 So, to do that we add resistance into our circuit.
34:01 I'm just trying to think if I can easily show that here yeah, so if you just think about it that LED is going to have very very low resistance and as we see here if I have very very low resistance our electrons can flow through really fast it's going to generate a heap of heat and energy in that little LED and that LED is going to fail because it can't actually handle that.
34:25 So, we need to actually add resistance and we do that by adding resistors and things in line with the circuit which if we think about our LED being after this little resistor on my screen if we increase the resistance we're slowing down that current we're reducing the amount of current and that won't burn out our LED.
34:44 Our LED will be getting the amount of current and voltage that it needs for the amount of resistance.
34:51 So, yeah while I did say you can't you don't necessarily control the current in a set circuit you can't just simply say I want it to supply this much current or like a battery to supply this amount of current that's just that's not how it works we need to change one of these fundamental rules to get that to change.
35:12 That was a bit of a detour from the question.
35:15 To answer the question I do recommend going to that other webinar I do talk about choosing wire gauges and that kind of thing a bit more in depth.
35:29 Jerry 3567 Mr Back to the Future, you guys are absolute legend for solving that question.
35:35 I had to like it was going to bug me all day if I didn't actually do it so yeah while it was ridiculous yeah we got an answer.
35:45 Philip Kan might be outside the scope of the discussion.
35:48 An electrical device only draws the amps it needs to run correct.
35:52 Yeah, so that yeah exactly what I was saying before because we have a set resistance of that component it's only going to draw x amount of amps unless there is a fault.
36:02 Yeah, so often what you'll have if something faults it'll generally be a short or an open circuit.
36:08 In an open circuit we are we are disconnecting something somewhere or we are increasing the resistance, so much that electrons can't flow.
36:18 Sometimes a component on say a circuit board might go faulty it might not completely you know burn out or disconnect, but it will become so damaged that it's or even like corrosion is probably a good example.
36:32 We get, so much resistance there that our current can't flow properly and we get no energy essentially.
36:39 Then on a short circuit end we're bypassing any resistance that's in our circuit.
36:44 If I go back to my display here if we have a look on the computer if we show here if I go to absolute minimal resistance you can see we get such a big flow of electrons things get really hot and that's why that's why fuses blow.
37:00 That's the whole point of them is they're you know rated to a certain amount of current and they're to stop short circuits from creating, so much heat and energy.
37:10 If we didn't have a fuse and you've probably no doubt seen people connect batteries just straight negative to positive there's such little resistance there that we get all this sudden heat transfer and heat yeah it's transferred the electrons are transferring into heat and you get things like sparks that's the you know the light and heat energy you know escaping and it causes bad things and that's why we don't want it in the car.
37:35 But we can see all that kind of reference from our Ohm's law, so yeah that's how a short circuit and open circuit sort of correspond.
37:43 It's still it's a set amount of amps, but because we're changing the resistance we're getting two essentially different problems.
37:50 In our perfect world we'll have our working component that'll have its set amount of resistance and we'll get a certain amount of current going through it.
38:00 Just going to go back to my questions I don't think I read through this completely.
38:09 So, Philip Kan, the reason I ask is because if a battery can supply 600 amps is there a concern of having the residual power with nowhere to fully dissipate? 600 supply amps, but only enough devices to use 200 amps.
38:24 Hopefully, that makes sense.
38:26 Yeah so, that's something we uh I do often see people think about that and uh you know think hey my battery is rated for 600 amps why can I only just disconnect this little led and something doesn't blow up? It's because we're only allowing a certain amount of that current to flow when we connect we're applying we've got resistance there and the electrons can't flow that full 600 amps.
38:52 So essentially that 600 amps is our electrons flowing really really fast that's the maximum flow that that battery can supply safely without you know things going wrong.
39:04 And, so we've got devices use 200 amps, so that's saying in your whole circuit your all your system with everything on you've got enough resistance that at 12 volt you're going to draw 200 amps.
39:17 So, we can actually use that calculation in our calculator uh excuse me sorry we've got 12 volts and uh, so it's 12 we'll say 12.8 volts divided by our 200 amps we've got very little resistance it's 0.064 ohms, but as I said when we have less resistance we get quite a high current draw and that's uh if you think about a starter motor we're essentially we are almost not a short circuit but a starter motor has very little resistance that's why it draws, so much current and we get things like you know 250-400 amps.
39:52 We're doing it quite quickly though that's the other thing.
39:57 So, yeah your actual circuit through the starter motor is quite low resistance and that's why we get yeah high amperage through that, but only when we have our starter motor in our circuit we only have uh we're only creating a circuit with that low resistance when the starter motor is on.
40:14 All other situations we've got uh all our other circuits that have quite high resistance that's restricting the uh electrical flow and we're not drawing anywhere near that it's only 10-15 amps and that is all that's going to be demanded, so yeah there's no there's no risk of that uh extra current going anywhere when a battery states uh 600 supply amps it's purely saying that that's what it's uh that it that's what it's capable of it can do that if we need to.
40:42 Um hopefully that wasn't too long-winded of an answer to that question this was quite a short webinar, but I figured it would be kind of short and sweet.
40:51 I appreciate the questions guys uh definitely helps me uh fill these out a bit more and yeah I do enjoy answering the questions.
40:58 If you've got any more jump on the forums and uh we can I can answer them there as well.
41:03 Also keep an eye out for those tools I'm going to try and do a few more of them um if you do like them let us know if there's any other ones that you want to see any recommendations.
41:14 Also make sure that you jump on our 2JZ giveaway that's a absolutely huge one that's been going on uh everyone here is excited about it I wish I could enter because I love my JZ engines and that is a huge one.
41:26 But anyway that's the end of this webinar I hope that has made Ohm's Law a bit more make a bit more sense.
41:32 It's a very simple thing it is you know it's a very it's simple maths it's just stating how everything is working together and it's just how we use it in our scenario that determines things like our current.
41:44 Again yeah thank you for coming I really appreciate it and looking forward to seeing you in the community.
41:50 Catch you all later.