00:02
So it looks like you have a question about how the junction rule works and how we can tell what the current flow will be at different junctions.
00:12
So you didn't include a picture of the actual circuit that you are looking at.
00:19
So i'm going to just look at in general what the junction rule is.
00:24
And i've made up an example circuit here.
00:27
And i hope that's helpful for you.
00:30
So if not, you'll need to resubmit a new question with the actual picture.
00:36
But i think explaining what the junction rule is and doing this example should help you be able to solve the issue that you may have on your circuit.
00:48
So here i have a common circuit.
00:51
It has two junctions.
00:52
A junction is wherever there's a split in the wiring.
00:57
So it's usually a three branch wire here.
01:02
So that's what i have.
01:04
It's basically if i was imagining that i'm traveling along on the road, i come into a fork in the road.
01:11
That's what we call a junction.
01:13
So there's a place where the current flow is going to split off in two directions would be a junction.
01:19
And then we also have the corresponding junction where the current is going to come back together into one current.
01:28
So our first step that we have to do is come up with what's the total resistance of our circuit.
01:34
And then we can find out what our total current flow is, which is what we need to know what the total current flow is before we can figure out how much is going to split each direction.
01:47
So the first step is to do a the parallel rule here.
01:52
I've got a 40 -oom and a 20 -oom resistor sitting here.
01:56
They're in parallel.
01:57
So i'm going to combine those.
02:00
And remember that when we have parallel circuits, we've got to do the 120th plus 140th method.
02:07
So i'm going to type that up so you have that for your notes.
02:11
So the first step here, i'm going to call this r sub one for the first loop here.
02:24
I'm going to do 120 plus 140th.
02:30
And i need to find the inverse of that because the total of a parallel is the inverse of the fractions here.
02:39
So i'm going to type this up so that you have that for your notes.
02:47
So let's see what that number is if i solve for it.
02:56
So 120th plus 140th and the inverse of that, i get 13 .3.
03:09
So that's how much we have for this, what we call the equivalent resistance for this part of the circuit.
03:19
And then what i have after that is i can treat this whole thing as one resistor that's at 13 .33 oms.
03:28
So i'm going to imagine that it's connected in series now because it's all one loop.
03:33
I've reduced this loop down to its equivalent resistance.
03:37
So i just have one more step to find the total.
03:43
And remember when we want to find, and i'm just going to call this r2, which is going to be the total amount.
03:50
So this second loop is going to be 10 plus 13 .33 plus 30.
04:01
Oops, i need to do a plus and dot.
04:08
And that's our total resistance.
04:15
Of, let's see, 10, 40, 53 .33 .33.
04:20
So now i know my total resistance of the circuit.
04:25
It's 53 .33.
04:26
I have the voltage.
04:28
So now i can use the oms law to find the total current flow.
04:32
So that's my next step here is using v equals ir, which is oms law.
04:38
And to find the current flow, i'm just going to rearrange my variables.
04:44
And it's going to be v as 9, and then i'm going to divide that by my total resistance at 53 .33.
04:53
So the current flow is going to be running about 53 .33 .3 by 0 .169 amps.
05:10
So that's the current flow now.
05:13
And that's the current flow up here.
05:16
So just to make it a little bit easier, i'm going to label where that's the total current flow, and then we can start looking at when is it going to split based on this junction rule.
05:28
So i've got 0 .169 amps to start with as it leaves the battery.
05:38
And due to the conservation of charge, that's how much has got to come back in.
05:43
So whatever comes out of the battery must come back in...