00:01
In this problem we are going to compute some equivalent resistance between two points a and b.
00:09
Okay, we have two figures, so let's do the first one.
00:15
The terminal points are like this.
00:20
We have a here, b here.
00:26
We have this parallel branch and another parallel branch.
00:31
Okay, let's get some new colors.
00:36
We have some resistance.
00:41
Here each 20 oms we have two here each 10 and we have a single one 30 oms now we see that this group is serious so this also serious and this is just a single guy and all are connected in parallel so first we are going to focus on this outer structure namely the fact that these three restance values are connected in parallel so we have one over something plus one over something plus one over something to the power minus one okay for the last one it is simple we just one over 30 for the second one we have 10 plus 10 because they are in serious connection and similarly for the first one 20 plus 20 plus 20 and that's it if we just compute this number we get 10 oms okay now the second figure is more intricate and we have the following we have a here b here and we have this diamond type of a connection so we have 20 oms here 15 oms here 13 oms here 30 here, 10 here and 15 here.
02:49
Okay, now from this figure it is not very clear whether this is a combination of series or power connections.
02:58
So in that case the trick is kind of really nice.
03:03
We are going to imagine that there's a power supply here or at least there's a potential difference of v here between a and d.
03:14
And there is this current that is generated by this potential and it sees this equivalent resistance value so we have v equal to i times our equivalent and using appropriate kirchow of equations we are going to find this value of our equivalent and now let us write some loop equations and some junction equations.
03:55
Okay, first we need to assume some directions for the currents.
03:59
Let's say this is i2 and this is i1, this is i3, this is i4, this is i5.
04:13
Okay, we will use the following equations.
04:18
So this is junction 1, so let's call j1...