00:02
All right, looks like you have a question about how do we find the total resistance of these two circuits.
00:09
I don't have access to what these resistors ratings are.
00:15
So i'm just going to do a general plan of how you can go about getting the total resistance in these two scenarios.
00:24
The main thing is to recognize where is the junctions to know if you have to use the parallel resistance rule or the series.
00:32
Rule.
00:33
So i'm going to mark where the junctions are to start with with red.
00:37
And so a junction is anytime we have a spot where there is at least a three wire pathway.
00:45
We have two of one's first one here.
00:47
And so that means that we're going to get a split in the current, and that means there's got to be some stuff in parallel.
00:53
We've got that here as well.
00:58
Got a junction there, a junction here.
01:01
Sometimes when we look at these drawings, you can get tripped up by these diagonals.
01:07
Like there's something different about it than when it's like this.
01:10
It actually doesn't matter.
01:12
The r1 and r2 are in series and then they're in parallel with this one, just like these three are in series, but this one is in parallel to those three.
01:23
So it's not any different whether we draw it this way or draw it diagonal like that.
01:29
So you don't need to get tripped up by that.
01:32
Now this is another junction right here.
01:34
That we need to focus on.
01:37
All right.
01:37
So what i'm going to do is i like to attack this in terms of loops.
01:42
So i have one loop right here.
01:45
Excuse me.
01:46
These are all in, they're all in a series together.
01:51
So my first loop is going to be adding up r1 plus r2 plus r3.
02:03
So that will give me the equals.
02:06
I need plus there.
02:09
So these three here, if we do that, we get a sum that we're going to use with this.
02:17
So the next one, let's say we'll call this, i'm going to call it a number, r4, just to keep track.
02:26
So my first is going to be like an equivalent resistor that we're going to call r4, whatever that total is.
02:34
Now i need to get this one.
02:36
And this is in parallel with this whole whole loop.
02:40
So my next one is going to be, so this is my first step, my second step i'm going to put right down here.
02:48
That one i've got to do one over r2 plus one over r4, whatever our total was with this other one.
03:04
And then the total resistance, remember we have to do the inverse of that.
03:10
And i know this looks a little messy with typing it out like this, but this is to the negative first power.
03:16
Remember, the parallel resistant equation is 1 over r plus 1 over r2, plus 1 over r3 and so on.
03:27
And to find the total resistance, you take the inverse of all those sums.
03:33
So that's what we have to do here.
03:39
So we take this total, called it r4, 1 over r4 plus 1 over whatever this.
03:45
Is inverse that whole thing.
03:47
Now tell us this whole loop now.
03:50
This whole loop has been reduced.
03:52
So i'm gonna call it r5, just so i can keep track of that.
03:57
Now notice that now i'm down to one loop, here to here, here.
04:02
This whole thing has been reduced down to, i'm calling it r5.
04:06
Well, this is in series, right? this is a series.
04:09
There's no junctions left now.
04:11
So i can do one more addition here.
04:15
These are considered in series, with each other, r1 plus r3, plus this new value that we just figured out that i've called r5 from right here...