what is going on everyone my name is codmore and welcome back to electronics episode 17 in this episode we are going to talk about series and parallel circuits which are extremely important to understand because whenever you're doing Electronics work you're going to be using either one or the other or even both at the same time and I'm going to try and explain them as best as I possibly can so I have two circuits up here now I have just some random resistors in these circuits but of course these don't have to be resistors these can be LEDs or any other electronics component because any Electronics component for the most part has resistance so even an LED has some internal resistance but anyways I'll just use resistors for these examples on the left here we have something similar to what we built back in episode number 8 or something like that where essentially we had a battery right here and then we had a resistor then we had an LED and then that just went right back to the battery after that means the electricity could just travel in one big loop just like this right here electricity is just going to travel in one direction in one one gigantic Loop something like this is called a series circuit and that's the only type of circuit that we've worked with this far but let's take a look at the circuit over here on the right this is a bit different we still have three resistors all the same resistors and we still only have one battery except electricity doesn't have one path it can travel through it can travel through this resistor right here it can travel around to the second resistor back to the battery and it can even travel all the the way through to the third resistor and back to the battery there's multiple paths for the electricity to travel through now we've never worked on something like this but something that has multiple paths for the electricity to travel through is called a parallel circuit and we will be working with parallel circuits very shortly but let's get the main differences about these two circuits because we have to understand when and why we use which type of circuit so I'll begin with a simple example in your house you have most likely quite a few kitchen appliances so you have maybe a refrigerator a microwave and we'll say a coffee maker and all three of them are just plugged into an outlet in your house so we can say that in this series circuit R1 is maybe your refrigerator maybe R2 is your coffee maker and R3 is your microwave and they're all getting power and they're all running just fine but then all of the sudden you decide to unplug your coffee maker so you essentially just remove this resistor you remove the coffee maker from the circuit and now electricity has no path to travel through electricity will try to travel but oops you unplug the thing and now it can't travel through it to get to the other appliances that means your refrigerator and your microwave both stop working just because you unplugged the coffee maker as another example let's say you have a string of Christmas lights so you can just picture that each resistor here is just another light in that string of Christmas lights they all work perfectly except when one of the lights burns out if say this Middle Light right here burnt out then all of the other lights are going to stop working because you create an open circuit now there's no pathway for the electricity to travel through so series circuits are actually a really bad design for many things like the wiring in your house that you plug appliances into and Christmas Lights of course because in a giant string of Christmas lights there's bound to be at least one light that goes out once in a while so we fix that by using parallel circuit Tre if we have the same setup of Christmas lights in a parallel circuit so picture each resistor here being a separate Christmas light in that Christmas light strand then they're all going to work perfectly and if the second or the middle Christmas light goes out then this pathway is broken however the other two lights are still going to work because electricity still has a path through the first light and it can still have a path through the third light here that means the only light that goes out in the Christmas lights are just going to be the middle one because it burnt out and now there's no path of electricity through the middle one and if we bring this back to your house let's say and each resistor was a different Appliance if you unplug one of the appliances then the other appliances will still have a path for electricity to travel through so that's a big advantage to parallel circuits now we have these two different types of circuits except there's some pretty big differences between them in a series circuit current which remember is I is the same at all points in the circuit where voltage can differ at different points in the circuit like we've seen before let me rewrite that that looks very bad differ so if we took a multimeter and we measured current at any point in this series circuit at absolutely any point and we did it properly then we would get the same exact reading in a series circuit current stays the same but voltage will differ so if we measure the voltage across this R1 right here we might get a different voltage from the voltage across R3 down here so voltage can differ but current stays the same now if we take a look at a parallel circuit however it's the opposite current can differ at different points within the circuit but voltage stays the same in a parallel circuit so if we measure the voltage across R1 right here and we measured the voltage across R3 right here and we measured the voltage across R2 we should get the same exact voltage reading however the current off of these multiple branches might differ R1 might have a higher current than R3 does so those are some pretty big differences that we're going to have to take into account in the future when we're working with this now let's talk about adding resistors what is the total resistance in a series circuit well it's just going to be our total I'll just do R Tau so the total resistance in a series circuit is going to equal to all of the resistances added up so in our case it would be R1 plus R2 plus R3 dot dot dot if you had more resistors so that's the total resistance in a series circuit what about a parallel circuit though parallel circuits are actually quite different in a parallel circuit 1 over the total resistance in a parallel circuit is equal to 1 over all of your resistance values added so 1 over r1+ 1 over R2 whoops 2 + 1 over R3 dot dot dot if you had more resistors and we'll do some examples with this that way we can understand the math maybe a bit better but for right now that is the difference in the total resistance and it's quite drastic now what this means is that if you add a resistor so if we add a resistor into a series circuit our total the total resistance in that circuit is going to increase it's going to go up that's pretty obvious because we're just adding another resistor onto this total value however in a parallel circuit if we add a resistor so we just add another resistor in another Branch or whatever then our total resistance R to is actually going to decrease the total resistance in the circuit is going to decrease and we're going to see this when I do an example in just a second now when you add a resistor in a series circuit not only does your total resistance go up like it should but your current actually decreases because you're adding more resistance and by ohms law V equal I are if we're adding more resistance then current must decrease but if we look at parallel you might have guessed it if we add resistance resistance total will decrease Therefore your current throughout the entire circuit is going to increase and remember current in a parallel circuit can be different at different points all right so we know the main differences between a series and a parallel circuit we've made a series circuit before but we haven't made a parallel circuit yet now let's get to some examples so we can actually understand how to calculate all this properly and trust me it's very important we have a 9V battery and we have some resistors in parallel so let's find the total resistance of the circuit now remember one over the total resistance is going to be equal one over all of our resistance values added up so in our case we're going to have 1 over8 + 1 over 4 + 1 over 2 and that is the same thing as I believe it should be 78 now now this means that our total is just going to be equal to the reciprocal of our result or 8 over7 ohms as our total resistance in the circuit now if you're on a calculator and you want to do this then you can simply do all of this work right here 1 8 + 1 4 + 1 over2 and just raise that to the power of -1 and that will get you the correct result if you're on a calculator anyways we now know the total resistance of the parallel circuit now let's go ahe ahead and find the total current within our parallel circuit now if we were in a series circuit we know that current stays the same at all points except we are instead in a parallel circuit so we can actually calculate current at different points first of all though I jumped ahead of myself let's find the current or the total current of the circuit total current by Ohm's law V equals I is going to equal V over R voltage over resistance we know the total voltage in our circuit is just 9 volts like I put it so 9 over our 87th which is our total resistance and that if we do that out on the calculator that is about 7.875 amps so that is the total current that is traveling through the circuit right here that's quite a bit of current 7.8 amps but anyways let's figure out how we get to this total current in other words let's measure how much current that each component each resistor is getting so we'll calculate it first for the 8 Ohm resistor and we can just use Ohm's law once again so we know that voltage stays the same so I is going to equal V / r as always so I is going to equal 9 Vol over and since we're calculating the current from just this one component we're going to use the normal resistance value so 9 over 8 ohms is what that would be and that's the current for resistor 1 we'll calculate the current for resistor 2 and the current for resistor 3 go ahead and do that yourself right now all right I've made a huge mistake that is not ohms these are amps of course we're not measuring resistance I is current so here are all the three correct currents that are passing through each resistor here and if we add them all up we get 7.875 amps which is the same thing as we calculated as the total current running through our circuit so that adds up that's proper that means we hopefully did everything correct and just to prove that voltage in a parallel circuit stays the same throughout we should be able to use ohms law once again to go ahead and calculate that for each individual resistor so for instance the voltage going through the first resistor is just going to be equal to the current going through the first resistor which in this case is 9 over 8 amps so 9 over 8 amps times the resistance value in this case it's 8 like so and that equals out to 9 volts and if we did that for the second and third resistors and any other resistor or component that's in parallel we would get 9 volts in this case because we have 9 volts running through our circuit all right that's awesome we've learned two different types of circuits and I'm sorry that this video is so long but I really have to push these two types of circuits cuz we will be working with them quite a bit now what happens if we added a resistor right here in the middle of our wire here and we'll say that that resistor is I don't know a 4 ohm resistor all right what I have here is the exact same circuit that I just drew just drawn a little bit differently that way you can clearly see that we have a parallel part of the circuit and if you thought of this parallel part of the circuit as just one little thing then we can see the series part of the circuit runs from the battery through this first resistor into this block of mystery parallel this and then comes right back on out just like a series circuit having one path of electricity so these three resistors are all in parallel that should be hopefully clear to see and we have this one outside resistor that is in series instead now in a series circuit our voltage doesn't stay the same that means we're going to have some voltage drop across this resistor so we're going to say that the voltage drop VD however to calculate the voltage drop across this first resistor here we're going to need the current going through the series part of the circuit now in a series circuit current Remains the Same everywhere so to calculate current we're going to need the total voltage which is 9 volts and we're also going to need the total resistance so remember how I said earlier that we can just think of this parallel part of the circuit as being just sort of its own Electronics component in a way so think of this as just one gigantic resistor now if we're going to think of this as one gigantic resistor we're going to need to figure out how much resistance it is and we already calculated that using 1 over the resistance total is equal to 1 8 + 1 4 + 1 2 and we got that the total resistance for the parallel part of the circuit is 8 over7 ohms so to find the total resistance in the series part of the circuit we just have to add 4 Ohms to that 4 Ohms plus this giant component that we said which is really the parallel part of our circuit so plus 4 Ohms and that will get us the total resistance in the series part of the circuit and I'll just keep it simple 4 and 87 ohms now still before we can calculate this voltage drop of this resistor up here we're going to need to find the total current running through the series part of the circuit this shouldn't be too bad because we already know ohms law we'll say is so the current in the series part of the circuit or essentially throughout this entire thing for the most part is just going to be equal to so is equals our voltage over our resistance we've used this many times before which is just going to be our 9vt power supply divided by the total resistance in the series part of the circuit which in our case is 4 and 87 ohms so divid by 4 and 87 ohms and if we do the math correctly that should be 1.75 amps so the total current running through the circuit is 1.75 amps now that we have total resistance and total amperage which we found using the total resistance we should be able to find the voltage drop across the 4 ohm resistor in series up here by the simple formula of V equal I so current which we found is 1.75 amps multiplied by the resistance of the resistor we're finding the voltage drop of which is 4 Ohms multip by 4 and that will equal 7 volts great so why did we find the voltage drop across this resistor well we found it because if the resistor is taking up 7 volts from the battery and the voltage in the parallel part the circuit must stay the same then what's the voltage in the parallel part of the circuit well since the resistor takes up 7 volts we're only going to have so many volts going into the parallel part and that should be easily found because we know we have our 9vt power supply minus the voltage that this resistor up here is taking so - 7 volts that leaves us with 2 volts so 2 volts should be coming from this resistor over here and into the parallel part of the circuit it therefore we'd have to redo all the calculations that we did just minutes ago to find out the current in each one of these resistors but nonetheless we now know that the voltage through each one should stay at a constant 2 volts instead of 9 volts because we have this pesky resistor here so I challenge you guys to go ahead and do the same calculations that we did just minutes ago to find the current through each one of the resistors make sure everything adds up properly the total current in the parallel part and if you can do that successfully then you know more about series and parallel circuits than you probably think you do I'm really sorry for the long video guys but it was really important that we touched a lot upon this and a lot upon the math that way we can do it fairly quickly when we get to more and more advanced circuits thank you guys so much for watching and I hope to see you guys in the next episode