What up? Everybody? Welcome to another episode and let's ask Paul the podcast
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all right, so if you're listening to this episode, you see the title,
it's talking about combination series and Parallel Circuits, and it is the third
I believe, yeah, in the episode series actually the fourth. We did
one episode on Ohlms Law, which you need to understand Ohms Law before you
even listen to this one. And then of course we did series circuits.
You need to listen to that, and in parallel you need to listen to
that before you even attempt okay, before you even begin to get into something
like combination Circuits, which is a amalgamation if you will. That's right,
I said it of series and parallels. Okay, So let's kind of well
assume that you paused here, you went back and listened to those episodes,
and again it's you know, the episodes are available over on any of your
favorite podcasts listening platforms. You'll find them in those episodes. So let's be
episode one seventy one, one seventy two, one seventy three, and this
is what obviously I guess will be one seventy four. I guess I'll hold
me to that. That's what I believe. It's what we're at in this
series. Okay, so let's talk a little bit about it. Assuming you
already understand how to do the Olms law, which we're going to rehash a
few of those things here, but understanding you know how to do that,
You've watched, you've listened to the podcast on series, and you listen to
the one on parallel. Some occasions in an exam, they might throw in
a very basic combination circuit. And what's a combination circuit, Well, it's
made up of both series loads as well as parallel and again you might have
what's called a parallel circuit, and within that circuit it has series circuits.
And so we always want to try to solve this and get this down to
the simplest equation and make it as simple as possible. So I'm going to
give you an example, and it's kind of going to be pulling together everything
that we've done in the previous episodes, So make sure you go back and
listen to those and again, if you have not listened to my series in
parallel version or the o'mslaw one. Then do me a favor. Go on
and stop now, because this is not going to do anything but confuse you.
Okay, Okay, So if you paused it and you went away,
you watch those other episodes or listen to them. You're now at four minutes
and twenty five seconds in. You can you've jumped back to where you need
to be. Okay. To make this simple, I want you to just
draw me a rectangle. Okay, just draw a rectangle, all right,
So you should be looking at a rectangle on the left side. I want
you to draw a circle right in the middle of it. So it's a
circle with the wall of the left side of the rectangle running right through it.
And we'll call that the source. Okay. So at this point,
you got a rectangle on the left side. You draw a circle that's right
in the middle of the left wall of the rectangle. It's a circle shade
that in draw it in colored in whatever you want to call it. We'll
call that the source. Now, the first loads that you're gonna have is
from the top to the bottom of the rectangle. I want you to draw
down and you're gonna draw one squiggly line, okay, and then you come
down and you draw another squiggly line and then connect each side of the top
to the bottom. So what you have is a line running from the top
to the bottom through the middle of the rectangle about a quarter of the way
from the left to the right. And you've got two resistant loads in there.
So draw those squiggly lines to reference the resistance load or some kind of
load. Okay. So that you just drew was a series circuit. You
have two loads that are in series, but they're connected to the overall parallel
circuit, which is that box. Okay, you with me, which is
that rectangle box. Okay. Now go to the all the way to the
right side of your rectangle. In that wall, I want you to come
down, draw squiggly line in it, and go down space and then draw
another squiggly line in it. So on that right side of this rectangle,
you have two loads and they are also in series with each other. So
what you have is you have two branches. You have the one branch in
the middle that we drew, which is branch A, and that has two
loads in series. And then you had the very right side of the rectangle
and I add you to add two loads in that wall. So now you
have two loads in series on that right side wall. So what you've drawn
now is a parallel series circuit. So the circuit runs around the rectangle,
but you have branch A that runs across the middle of the actual rectangle,
and then at the end you have two loads again that are in series that
are running across the right side of the rectangle. Both of these branches are
in parallel with each other. Okay, you have branch A in the middle,
and you have branch B, which is the far right side of your
rectangle. So hopefully i've paid in you that mental picture of what we're doing
here. Okay, Now, so you have four loads here. Now you
have two in branch A in the middle, and you have two in the
right wall of the rectangle that is branch B. Okay, Now, I'm
going to give you some values so that we can work this out. So
we're not going to give you the current and I'm not going to give you
the resistance of the entire circuit, but i will tell you the voltage.
So the voltage is one hundred and twenty volts, and I will give you
the resistance value of each one of these resistance loads or these loads in the
equation. I will give you that, but I'm not going to tell you
the voltage and I'm not going to tell you the current, because you're gonna
have to work that out. And that's why it's so important that you have
watched our series. I keep saying watched, that you listen to my series
podcast and you listen to the parallel podcast in order to understand what we're doing
here. So I'm going to give you the resistance. So the first one
on the top of the branch A is twenty homes, and then the bottom
one on Branch A, that's the one cutting through the middle. That one
is forty homes. And then on the right side, the top one in
Branch B that is ten homes, and then the bottom one in Branch B
is fifty homes. Okay, so we have twenty, forty, ten and
fifty. Ok Now, that's what we have so far. We all know
anything about the voltage at any of these loads. We don't know. We're
not worried about the current any of these loads right now. We're just simply
we're given the resistance. And this is very common to give you this way.
Good news is we do know we have voltages values, and we do
we have some stuff that we can work with. Okay, all right,
So the first thing we want to do is we want to start with the
branches, and since we have loads, and we're working on each branch separately,
because each one of these branches, if we treat them separately, it's
nothing more than a series circuit. Right, So remember what we said about
the series circuit, if you remember earlier when it comes to series, when
we're doing series and we're dealing with the resistance, what does it say in
series? In series, the resistance is what it's additive R one plus R
two plus R three. So it's pretty straightforward, right, So let's kind
of work this out. So you always want to redraw this each time,
same way, draw the rectangle and then you combine your lost. So in
the first branch it's twenty oms and in the bottom one is forty oms,
so it's simply twenty plus forty. That's sixty oms. That's Branch A,
right, and then in branch B exactly the same. We're working the series
part first, and that is ten plus fifty. So if I redraw this
rectangle, and I draw the circle for the source back in the left wall
and just put that s for source. And now the resistive that I draw
through the middle is one line down, big squiggly line, and then draw
it to the other side. Now that resistant load is sixty homes. And
then the back right side, I combine the fifty and ten. So now
that one is sixty homes. Pretty straightforward. Right, So now we have
less complex combination circuit. We still have a parallel, but now we don't
really have any series anymore, right because now what we have is a simple
parallel circuit. We took the series, he worked them down and now they're
part of a parallel. We don't have any series anymore. These are it's
now purely a parallel circuit. Now here's the beautiful thing about it. When
it comes to the parallel, you remember we have multiple ways that we can
solve this to get our total resistance. Okay, because we want to get
that first. It's going to get our total resistance because we're right here,
we can go in and work that out. And we got to remember that
when it comes to total resistance, we need to get the value for our
resistance and then we can, you know, we can work through the rest
of the stuff and get everything else we need to work and get our equations
in our values because we're going to solve all the everything in here. We're
going to find out what the the the voltage is, we're going to find
out what the amps are at each one. But we're going to work these
out. Okay, So remember the first way that we could do this,
that was a simple method. If you remember back in the Parallel podcast,
it was our one times R two and divided by R one plus R two.
Okay, pretty straightforward. And in our case, we're using branch A
and branch B. So it's R a times RB divided by r a plus
RB. So what did we say. There's sixty oms, right, So
it's sixty times sixty. That's the top part. So sixty times sixty is
thirty six hundred. That's the top, and then the bottom was R A
plus RB. And the reason we're using A and B is because we said
this was branch A and branch B. But again, don't get confused because
it could be R one R two whatever your exam may show you, it
doesn't matter. Same thing it's the loads that are given. So in this
case, sixty plus sixty is one twenty. So if you divide thirty six
hundred into one twenty, that's going to give us thirty oms. Okay,
so that's our total for this for this one, it's thirty oms okay for
this parlevel. Okay, Next, the next thing we could do? Okay,
well, is there an easier way to do this? Well, yeah,
because both of these are sixty. Remember what we said we could do
if they're equal value, then you just take one of them, which is
sixty, you divide it by two and that's thirty. So you could get
the answer that way as well. Makes sense. Yeah, but there's also
a third way you could do that if you listen to my parallel, there
is another way to do it. And and in this case it was our
one over RT equals one over R a plus one over RB or one over
R one plus one over R two, depending on what you're what you're doing.
Okay, so the common denominator I waited one of the ways to do
it. The common denominator for this is sixty because they're both sixty, so
that would have been one over one one over sixty plus one over sixty would
be two over sixty, right, so two. So one of the ways
to do this now is to invert it, right, and so it'd be
sixty divided by two, it would be thirty, right. Okay. So
there's many ways that you could do this, and I mean you could even
work it out even further. Another way to do that, because we just
did it that way is the common denominator way. But one other way to
do this, which is which we explained in the parallel podcast, was to
take the full values that you'd get with the decimals and work that same formula
one over our T equals one over our A plus one over are b and
again, so this case would be one divided into sixty, which would be
point zero one sixty sixty six six sixty sixty six. Uh. And then
of course that would be the value for the one over that, And then
of course then you'd have the other one over sixty, which would be the
same one divided into sixties point zero one six six sixty six six sixty six.
And so that gives you a point zero three three three three three three
three two. And so when you divide one into that, that gives you
the thirty ohms, right, So I mean that's a longer way to do
it. So that's why in the parallel podcast, I explained how to do
the the You know, when you are doing the value and you actually work
it out with what's called a common denominator. In this case, they both
were sixty, so there wasn't that sixty is their common denominator. So again
and so you just added how many times does it go into sixty? One
for each, So that's one and one, it's two. So that's why
you get the two over sixty. You invert it sixty divided into two.
That's how you get to thirty. Right. So there is couple ways you
can do this. I showed you the very long way with your calculator.
You just have to make sure you use all of your decimal points or all
of your spaces after your decimal point, otherwise the numbers won't add up exactly
as what it gets you when you do the denominator value. Okay, the
one where you use the common denominator. Hopefully that makes sense. Go back
and watch the parallel one I mean, excuse me, yeah, Parallels podcast.
Go listen to that and it'll make more sense. Okay. So let's
go back and solve the missing variables in our circuit. You remember our circuit,
which we knew was one hundred and twenty volts at the source, and
the first load on branch A was sixty oms, and we need to find
out what the voltage is, and we need to know what the current is.
And then the second load, which is in the right side of our
rectangle, if you will, that was sixty oms of resistance. Okay,
and we already know what the overall is, right because the overall we can
calculate out and find out what the overall is, okay, And so let's
now kind of do this, okay. So let's see here, first thing
we want to solve for Let's go on into the loads in the branches.
Let's do branch A, so we know it's sixty oms. So we want
to solve for what the current is, and we want to solve for what
the voltage is, right, all right, So the one thing to remember
about volts, the voltage one is easy, okay. Remember, for parallels,
the voltage across each branch is equal to the voltage at the source.
So if this et the total voltage is one twenty and that is given to
us. Then we know that it is one twenty at each one of these
branches. So that's easy. So we know it's one hundred and twenty vaults
at both of these branches. That's easy. Now we want to solve for
the current. Well, now that we know the voltage and we know the
resistance, that's easy. Then we can solve the resistance, I mean,
the current at each one of these locations. Okay, so how do we
do that? Remember your your omes all. Remember the circle with the line
through the middle of it to separate the top from the bottom, and then
there's a line down from the middle down to separate the lower left quadrant from
the lower right because EI R. So to find out now what the current
is, it's simply you put your finger over the I and now it's E
divided by the R because we have those values. So it's one twenty is
the E. We just calculated that, and we're going to divide that by
sixty and that gives you two So that is two amps. So that first
load in our equation is one hundred and twenty volts, two amps and sixty
oms. So now let's do the branch B same thing. We know that
it's one twenty, and in fact it'll be exactly the same because the same
is on branch A is exactly the same is its own branch B, so
we don't even have to do the math. Then this one is also two
amps. Okay, So now that we have branch A, we it's one
hundred and twenty volts, two amps, sixty oms. Branch B is one
hundred and twenty volts, two amps and sixty olms. Now we can do
the source, which we know is one twenty. But now remember what we
said to find the total current. Remember, in a parallel circuit, the
current is additive, so you add the total of each load. So it
was two amps on branch A, two amps on branch B. So guess
what the total amps are. You guessed it four ams, So it's one
hundred and twenty volts and four amps. Now what about that resistance. Now
remember what it's said to do to get the resistance to total resistance. Okay.
Now, one of the things that we saw here is is okay,
so the total resistance is the little voltage divided by the total amps. Right,
So what was the total voltage one twenty. What were the total amps
one twenty divided by four, it's thirty. So thirty is the total resistance.
Now we already knew it was thirty because we already kind of did the
total resistance anyway. We already did that earlier, and that's what we came
up with the thirty oms. But this is a way you do it again.
Once you have all the variables in place, and once you know the
amps in that scenario, and once you know the voltage, then you can
solve for the olms. We just showed you how to do it if you
didn't know what it was. Now let's say that I had the omes and
you solved, and you said, well, I have one hundred and twenty
vault source and you've already calculated what the total resistance is, then you can
use that to solve the whole amps. Anyway. For example, if I
know the vaults and I know and I know the total resistance, and I
don't even know what the current is, I could solve what the current is
at the source right by simply using the owns law. So if I'm solving
for current, it's going to be the one twenty and I'm going to divide
this into what was the total resistance which was thirty, and that gives me
four and that is the amps. So, as you can see, you
can solve the equation many ways depending on what they give you in the question,
right, And so what's important is to really realize how to work each
one of these out itself and to be able to calculate it out right.
Now, here's the funny part. Maybe that's how you work it down all
the way to the end and find out what the total voltage is, the
total current is, and total resistance and you worked each of these brands is
down. Okay, but what if you wanted to go back now and you
say, well, you know what, since you gave me the resistance at
each one of those loads, which was twenty, forty, ten and fifty
right originally that's what they were originally, then guess what I can actually find
out what the actual voltage is, how it breaks down right, using owned
law across each resistive point. It's pretty cool how you can do that.
So if we were to go backwards now and put that original equation back in
there, and you say, well, Paul, can you can you tell
me since what is it actually at each one of these these points? Okay,
well, since we know the current doesn't change, right, so when
we have a resistance value for each one, then we can simply do what
to find the vault. To find the voltage at the first one, which
is the twenty oms, it's simply twenty times what the current, which is
two, so that one is forty volts. So twenty times two is forty
So the voltage drop at that first resistor is forty volts. Then you could
go back to the second one if they ask you say, hey, what's
the voltage drop at this one load point? Well, you know the current
stays the same, so it's forty times two, and that means that one
is eighty at that one. And then you go to the third one,
which was I believe ten homes, and it'd be ten times two and that
would be twenty volts. And then the last one, which was fifty,
it's fifty times two, which is one hundred volts. So I can tell
you exactly what the voltage that's dropped at each one of those loads at that
twenty homes forty, ten and fifty, right, So it's not nearly as
difficult as people want it to be. You just have to work out the
values and find out each little component and take your time and work them out,
and it becomes pretty simple process to be able to do it. And
it can be complex where you have what appears to be a simple series,
but then it has parallels off of that. Well, you want to take
the parallels and try to solve them down into what you want to solve them
down into a simple series circuit and try to make it as simple as possible.
So you might have a parallel series circuit where you have parallel but you
have series within it and you're trying to get it down to a simple parallel
circuit. Or you could have a series circuit that has parallel circuits added into
it and you're trying to get it down to a simple series circuit. So
one of the things to remember is how I call it. Like for example,
if I tell you that I want you to solve this series parallel circuit,
then that tell yous that the circuit is probably a series circuit with a
parallel component, and you want to take the parallel and get it down to
a series. Or if I tell you there is a parallel series circuit.
Then it's probably a parallel circuit with some serious circuits in it, and you
want to solve the series ones to get it down to a simple parallel.
Does that make sense? And so you really got to pay attention what they
ask you when it comes to the actual how they present the question. Okay,
that's kind of one of those things that's kind of a little tip for
you that kind of puts you into the right perspective. Okay, all right,
folks, that's pretty much it. When it comes to combination. I
would not let them freak you out on an exam. You know, My
old rule as always save the calculations for last because they take the most time.
If it's a parallel do your best to possibly use the common denominator method
if they'll if you know, that's kind of advice on that, but don't
let it panic. It's again, usually on an exam, it's maybe one
or two questions, if any. In the real world, you'll probably never
have to do this unless you're into electronics and whatever that type of thing.
But it's something that you know, if you listen to this, you know
this podcast, you probably had an interest in understanding the basics and maybe you
are just taking an exam, and and many times they ask you stuff on
an exam that you may never do in your life in the real world.
Just remember it's an exam and they're going to have to ask you to make
sure you understand. And usually these questions will fall under general questions or trade
knowledge, not so much a code look up or a code calculation. It
is kind of just trade knowledge that you learn in your apprenticeship programs and things
like that. So you might have already put your hands on a lot of
this, So this might not be you know, new to you. This
might be old hat to you and that type of thing. So anyway,
hopefully you got something out of podcast. Remember if you have questions you want
to submit, all you got to do is go to Paul Abernathy dot com.
We love to take your questions. I answer tons of questions. There
are hundreds of them that come in a month, and I'm just doing my
best to try to keep up with all of them. Some cases I have
one hundreds come in a week. Again, a lot of them I reply
back via you know, email, And then of course we have plenty of
them that are stacking up that I'm doing for upcoming podcasts. It's just so
hard to be able to do them. It takes time. Podcasting is my
favorite platform. I love it more than doing videos. I love to just
sit and talk, and I find it a challenge for me to try to
convey a mental picture knowing that you're just listening to it, and some people
will get it and some people won't. Some people get confused. I get
it, and I understand that, but it's it's kind of a challenge for
me to try to convey a mental picture. So for those that got it,
you're welcome. For those that didn't, I sorry. There's videos on
our fast Tracks tube that explain series parallels and combinations. I urge you to
check them outni't next time, folks, Stay safe, God bless and we'll
catch you on another episode of Let's Ask Paul.