Complete Guide to Series, Parallel, and Combined Electrical Circuits

hey guys hope you're well so this is going to be one of the most important lessons when it comes to electrical

circuits I'm going to explain all the foundational things that you need to know to really understand this chapter

quite well so we're going to be looking at quite a few things we're going to be looking at a series circuit and I'm

going to teach you some amazing things about that we're going to look at parallel circuits and then we're even

going to look at circuits that have series and parallel all combined and I'm going to show you some interesting

things when it comes to how to know what the current and the voltage values will be okay

so stick around there's quite a bit here so here we have an electrical circuit now the way that electricity moves is it

always starts at the long line the positive one and it flows out of that now remember the electricity can never

go through a voltmeter it never does that so it doesn't go that way it goes this way then it goes through this

device over here which is an ammeter which measures the current the electricity then carries on carries on

carries on go it gets over here now remember it cannot go up this way because it never goes through a

voltmeter so it rather go straight like that and then it keeps going keeps going keep going and by the way this is a

resistor and a resistor like we've seen in previous lessons there's anything like a tap a device like a light bulb a

television a microwave it's any type of device then it goes through another ammeter over here

then it goes through another type of resistor and then it keeps going goes through another ammeter and then goes

goes through another ammeter and then a completes the circuit so can you see that the electricity only follows one

path there was no area where it decided to go on a different path for example later on when we look at parallel we'll

see that the electricity is going to be able to follow different Pathways that did not happen in this one so that is

what a series circuit is it's when the electricity only follows One path

okay now the way that a electrical circuit works works is that the voltage

or sorry the battery supplies voltage so the battery gives the voltage to the charge those charges can then go to the

go through the circuit and they can use that voltage or energy that the battery has given and it can use it to go

through resistor number one and resistor number two so for example if this voltage is 8 volts then what maybe

happens is that this voltmeter will be 2 volts and then this one would have to be six volts can you see that because what

happens is that the battery gives 8 volts and then the Chargers use the eight volts in the circuit so maybe this

was a light bulb so it only uses two volts and maybe this one is a fridge so it uses more energy so it uses a six

volt okay so to calculate this voltage value well there is a Formula that I want you

to look at the voltage value or V is going to be equal to the voltage or let's say the sum

of voltage or voltages in series plus and then I'm just going to say

voltage of parallel branches okay but that part there is

gonna be we're gonna have to talk quite a lot about that I will talk to you about that when we get to parallel

circuits okay but I just want you to write this one down so long and this formula is going to be really important

for us to use they won't show you this formula in class but it's something that I've

um come up with to help make this section A little bit easier and when I say V you need to understand

when I say V I was talking about the battery voltage but your teacher might not always call it V maybe they call it

V1 and then they call this one V2 and then they call this one V3 so when I say V I was talking about the battery so the

voltage of the battery okay that's probably what the formula should rather say okay but stay tuned

because we're definitely gonna have to talk about this one it's something interesting that I need to tell you

about this one so can you see that um if you wanted to work out the voltage of the battery you could say the sum sum

means when you plus all the voltages in series so that's two volts plus six volts and that would have given

us 8 volts and that's where we got eight volts okay so there we have it I've just

written something down and then this part here means that there's something important that we need to talk about

when we look at circuits in parallel the next thing I want to talk about is the current so in parallel I mean in series

which is the type of circuit that we have here the current stays the same current stays constant so what I mean by

that and you can think about it we said that electricity starts over here and then it flows this way so maybe we have

a total current of 5 amps now over here it's still going to be 5 amps and then it gets over here

and it's just going to remain 5 amps all the way around the current does not change in series

so that means this would be 5 amps on this emitter it would still be 5 amps over here it would be 5 amps and over

here it would still be 5 amps so at the moment all that I want you to remember is the following

so let's have a look here now and let's remember the rules that we've learned so far so what we can say is

that the voltage of the battery which is V in the sixth circuit is the sum of all of the voltages in series so this

this circuit is all in series it starts here and then it goes like this and then it goes through R1 it goes through R2 it

goes through R3 and then back to the beginning so you see that we never change the path we didn't go off on a

different pathway the current never had to split and so this is a series circuit so in so we can say that it's the sum of

all of the voltages in series so that's going to be V1 plus V2 plus V3 and then it says plus all the parallel branches

but there aren't any parallel branches and so we're just going to leave it like that so that's something important for

the circuit and then in series current remains constant that means that the current over there is the same as the

current over there which is the same as the current over there same as A4 and the same as A5 so all of

those would be the same so the only summary that I want you to remember now for series circuit is that in series

in series current remains

constant and then that formula that I showed you about the battery or that you are going

to use for all circuits so it's sum of all sum of voltages in series

plus parallel branches which we haven't looked at yet we haven't looked at that and there's

something special that I need to show you there okay so let's have a look at the circuit so the circuit always starts

here at the positive terminal and it goes like this and then it gets here now because it gets here and by the way it

doesn't go this way because it never goes through a voltmeter now when it gets here it can go two different ways

so some of the current is going to go that way and some of the current is going to go that way it then joins

together and Carries On like that

so because the current had to split over here we will say that this area is called a parallel or that's a parallel

part of the circuit okay then all of the rest well that's still going to be in series that's still in series okay so

that part's in series and then that part is in parallel guys a few interesting things now here

it is in parallel the voltage of each pathway is the same but now we

need to talk about that carefully so let's say for example we've got this part of a circuit okay and then some of

it goes this way so there we've got a resistor and then there we've got another resistor okay and and

there we've got that now let's say we've got a voltmeter V1 and another voltmeter V2 so what I've just told you is that in

parallel the voltage of each path is the same so that means that V1 and V2 will be the same okay but now be careful

there's something very interesting we're going to talk about but first let me just show you that this

is parallel so the electricity would go over there and then some of it would go this way and the rest would go this way

and then it would combine again and go like that so when it's in parallel the voltage in that in the top branch is the

same as the voltage in the second Branch But Here Comes the most important part if we have a circuit that looks like

this where in this top Branch we've got three resistors for example and in the bottom Branch we only have one resistor

so let's go call this R1 R2 and R3 and let's call this R4 and let's say we had a voltmeter over here V1

V2 and V3 and then here we had a voltmeter called

V4 but let me just show you that this is parallel so here you've got this yellow

circuit arriving over there and then once you get over here well that's when the current can then split so some of it

would go that way while the rest would go this way it would then join up to go that way so the rule that I showed you

says in parallel the voltage of each pathway is the same I didn't say that every single device has the same voltage

it is the total pathway okay now would you agree that from here up to here that is in series why because that green

pathway cannot split it's only going through there so that part from there to there that is called series

okay so to be able to work out the total voltage

of this pathway now the rule that we spoke about it says in parallel the voltage of each pathway is the same

so let's look at this Pathway to work out the total voltage of that pathway you are going to plus all of them

together so for that pathway you are going to plus all of those voltmeters together because this part

over here is actually series from here up to here that is in series because this the current can only go like that

it can't split it only goes through R1 R2 and R3 so to work out the total voltage of that pathway

you add them together V1 plus V2 plus V3 now whatever that total adds up to maybe that adds up to I don't know 12 volts

maybe then that must be the same as the voltage of all the other Pathways have a look here in parallel the voltage of

each path is the same so that means that this pathway would also have to be 12 volts so let's practice this a little

bit so for example if you have something like this and you've got a resistor and then you've

got another resistor and then um down here we've only got one resistor okay let's actually just do this okay

now if this voltmeter here let's say that V1 that let's say that's a two volt let's say it's measuring 2 volts and

let's say this one is measuring um seven volts then you've got to try to figure out what is this voltage okay so

try give that a go try think about that well the first thing to understand is that electricity would normally flow

over there and then some of it would go this way and the rest would go this way it would all join up again and carry on

and you could imagine the electricity is flowing in that direction so this is parallel so what does our

rule tell us in parallel the voltage of each path is the same so in this top path

there's two voltmeters so you'll just have to add them together so for that path it would be so that would be two

plus seven which is 9 volts so that that's that pathway so that means that this pathway would also have to be 9

volts but this pathway only has one voltmeter so this would also be nine volts let's look at another example

let's say we have something like this so once again this is parallel the electricity would flow there and then

some of it would go this way the rest would go this way oh let's say that this is R3 and R4 and then it would carry on

like that so if you look at this Branch this pathway over here if you just add the

voltages together so the voltage of that path would just be six plus two which is 8 volts so that

means that this path must also be 8 volts they've told us that this one is already three volts so that means that

V1 would have to be 5 volts why because then if you look at this pathway if you look at that pathway it would be three

volts and then 5 volts which would give you 8 volts and so the voltage across this pathway will now be

exactly the same as the voltage across that pathway okay so that's what I want you to know for now in parallel is that

the voltage of each path is the same so for this circuit we will say that V1 is the same as V2 because that's a

voltage and that's a voltage okay the next thing is that you can see there's this voltmeter number three over here

which is measuring all across there to there so it's measuring the entire parallel pot so that one is also going

to be the same as V1 and V2 you're not going to say V1 plus V2 you're actually just going to make it equal to V3 like

that okay then the next thing is that can you see that

A1 and A4 are in series they not in parallel they are in series they are part of the main circuit now we know

that in series current remains constant so we could say that A1 is the same as A4 okay now let's quickly talk about A2

and A3 let's see what happens there so let's imagine that we've got let's say there are people that are busy

walking so let's say um oh no let's just stick to normal electricity let's say the current

flowing over here is 5 amps 5 amps of current now when it gets to the spot some of the

current is going to go this way and follow the green pathway and some of the current is going to go this way and

follow the blue pathway okay now let's say for example that two amps goes this way well then what happens is that 3

amps will go this way so that when you add these two numbers together it still adds up to five

the two amps is then going to go all the way through here and the three amps is going to go all the way through here and

then they're going to join together over here again and then carry on as 5 amps okay so when you are in parallel those

currents do not have to be the same okay but they will add up to the total current in the main circuit so here's a

little activity that I want you to try so what we have here is we've got five amps of current

approaching now let's just see if this is parallel so the current gets there then some of

it would go this way and then the rest would go this way and then it would carry on again so let's actually put

another little ammeter over here let's call this one um let's call this one

A3 okay so what they've told us is that the current over here is 2 amps okay and

they've also told us that this is a four volt and they've told us that this is a one volt so the question says the first

question says determine A2 so A2 is over here so how much current is Flowing there

well we started off with 5 amps and how much goes this way well if you look at the ammeter reading it's two amps so how

much is left over well 5 minus two is three so that means three amps goes this way so any ammeter that you connect over

here will be three amps so that would be the answer 3 amps over there okay and we're also going to say

determine A3 right the next question says determine V3 so V3 is over here so now we've got

to go back to our rule in parallel which says that in parallel the voltage of each pathway is the same so if you look

at this top pathway what is the voltage well there's only one device and so the voltage of that pathway is 4 volts that

means that this pathway must also be 4 volts this whole path has to be the same as

this whole pathway so so the blue pathway must also be four volts

so if this one over here is already one volt then that means that V3 would have to be 3 volts V3 would have to be 3

volts because then you've got three volts over here plus one volt over here which gives you 4 volts and that'll be

the same as this pathway over here then the last question so let's just answer this three volts this question is is

what is A3 well A3 is over here so what happens is that the 5 amps enters 2m squint this way three amps goes this

way and then it all comes together again over here and then carries on as 5 amps remember in series current stays the

same so that would be 5 amps so what I was trying to show you here was that A2 plus A3 A2 plus A3 will be the same as

whatever the current is in A1 okay and also just remember that A1 and A4 are the same so we could say that the sum of

parallel currents is the same or is equal to the current

in the main circuit now when I say main circuit I'm talking

about this part that is in yellow okay the part where it has not split up so the sum of parallel currents so what I

mean by that when you say sum it means plus so when you plus the parallel currents together so two plus three

that'll be the same as the current in the main circuit and so there is our next rule the sum of currents in

parallel is equal to the current in the main circuit okay so that's what I've showed you there so just remember these

two rules and then the next thing I want to talk about is this formula that I showed you here so to calculate the

voltage of the battery you take all the voltages in series now if we look carefully if we look at all the part

that's in series which was all the way up to there and then it was also this part there are no voltages okay so we

just ignore that part and then it says all of the parallel branches but now here's where you've got to be careful

where do we see parallel well the parallel part is over here so you only choose one of them M because you can

either choose V1 you could either choose the total branches you could add so you either choose the total path of this top

one or you choose the total path of the bottom one or you just choose this one over here

so the battery voltage you're either going to make it equal to V1

or you could make it equal to V2 or you could make it equal to V3 remember they all equal to each other anyways but just

don't go and don't add all of these numbers together no you only choose one of them okay now let me show you

something else that's quite interesting so you could say V1 is equal to that or you could say the battery is equal to V2

or you could say that the battery is equal to V3 and we would have normally added any voltages that are in series

but we just said that there weren't any so let me show you some examples all right so we've said here that the

battery voltage which is over here is equal to the sum of all of the voltages in series but if you look at the circuit

there is nothing there are no voltmeters in the series you can't say this is one of them because that is the battery's

voltage so we don't have anything over here then you're gonna plus all of the voltages or the parallel branches so

if you look at this top pathway over here what is the voltage of that path well the voltage of that pathway is just

going to be 3 plus 2 which is 5 volts so we've learned that in parallel the

voltage of each pathway is the same okay so that means that V1 is also going to be 5 volts because this pathway only

has one device okay so once again we've said that there's there were no parts in series

over here okay I know that um I know these two are in series but they also part of the parallel Branch so we don't

include we don't include those over here okay now okay so the parallel Branch um we've got this parallel part of here

and so what we said was when you're busy calculating this formula over here and for this parallel

Branch you only choose one of the branches so you could either choose the top Branch so then you would say five

volts over here or you would choose the bottom branch which would obviously also be 5 volts or you could choose if they

ever connected a voltmeter like this then you could also just choose that one but that one would also be 5 volts okay

so this battery would only be a 5 volt battery so the battery would be 5 volts in later parts of this lesson we're

going to look at ones that have series and parallel combined I'll prove it to you

um over here here you've got series and you've got parallel combined okay so let's move on to this one now so now

we've got a couple rules that we can now remember um right so let's see what happens here

so it is here in parallel the voltage of each pathway is the same so let's first see how the circuit works so the circuit

always starts by flowing out of the positive terminal so there it goes there it goes flows down here gets to this

point over here it doesn't go this way because that's a voltmeter now some of the current is going to go this way some

of it will just go this way and then the rest will go this way it would then combine again to go into one current so

we are told in parallel the voltage of each pathway is the same okay so look at this green pathway how many voltmeters

are there well there's only this one okay if you look at the blue one how many voltmeters are there is also just

this one and then if you look at the purple one there's only just this one so it says that in volts in parallel the

voltage of each path is the same so this means for this circuit V1 will be the same as V2 which will be the same as V3

okay and that'll also be the same as if you look at this V4 it's connected from there to there can you see these lines

okay so that that V4 is connected all across the parallel part so that V4 is also going to be the same like that okay

you're not going to plus them together nothing like that right the next part says that the sum of the currents in the

parallel in parallel is equal to the current in the main circuit so what I mean by that is

if we have let's say for this A1 over here let's say we have 12 amps okay now let's say 4 amps goes this way

and let's say six amps goes this way then that means two amps would go that way because 4 plus 6 plus 2 is 12 okay

and that's what we're saying here the sum of currents in the in parallel is equal to the current in the main circuit

so A1 is the same as A2 plus A3 plus A4 okay and then also remember that A1 and A5 are the same

because they are in series and in series we know that current remains constant okay the next thing the voltage of the

battery which is over here will always be equal to the sum of all the voltages in series so look at the yellow part is

there any voltages that you can see there no there's nothing so we're just going to scratch that out

plus all of the parallel branches but now for these parallel branches you only choose one of these you don't choose all

of them you just choose one of them so you could say that the battery's voltage then

will be the same as V1 or you could say V2 or you could say V3 or you could say V4 okay so in parallel we could say the

following that the voltage of each pathway is the same and the sum of currents in parallel is equal to the

current in the main circuit what that means this part of here is that if you have for example 5 amps and then if two

amps goes this way well then 3 amps has to go the other way okay now we're going to start looking at

combined circuits so we're going to keep all of our rules with us now okay so here we have a combined circuit

and these are all the different rules that we need to know okay so let's see how the electricity flows

so electricity starts by flowing out of here and it goes goes goes goes goes goes through this device it doesn't go

this way because that's a voltmeter and then it goes here and it gets to this part of here then

some of the electricity will go this way some of it would go this way and the rest would go this way and then this

would go like that okay so let's start with this part of here in series current remains

constant so remember series is the part that is in yellow so we could say that A1 is the same as A5 so we could say

that okay so A1 is the same as A5 and in the next lessons we're going to be doing actual

examples with numbers now let's have a look here in parallel the voltage of each pathway is the same

okay so in parallel the voltage of each pathway is the same so we could then say that

um V2 V2 is the same as V3 which is the same as V4 which is the same as V5

Okay so we've looked at we've looked at this one then the sum of currents in parallel is equal to the current in the

main circuit so A1 will be the same as A2 plus A3 plus A4 and then lastly we've got this rule that

we have at the top here which says that the battery's voltage is going to be the sum of all of the voltages in series

okay so the battery voltage is going to be all of the voltages in series so if you look in series we've got this

voltage meter yes we can say V1 then it says Plus now we look for all the parallel Parts

but this parallel part you only choose one of those voltmeters so we could choose plus V2 or you could choose V3 or

you could choose V4 or you could choose V5 but don't choose all of them you just choose one of them okay