00:03
All right, so this time you have four different circuits that you want us to work through.
00:07
Again, bir chart.
00:09
That's how to do these.
00:11
They're all, well, we have three in series, one in a combo circuit.
00:17
So i'm going to solve a couple of them here.
00:21
Since there's four of them, our video would get way too long if i was going to sit here and number crunch every one of them.
00:28
So i want to give you time to practice these, not just give you.
00:33
You answers as well.
00:34
So that's part of this too.
00:36
So i've got this one set up for letter a.
00:41
I've got six oms.
00:42
I got two oms and a four ome resistor.
00:45
We also know on the two oom resistor what voltage is, it's 20.
00:49
So we'll put that into our table as well.
00:52
So this, you need to practice this.
00:55
Just writing all the numbers into the table and then saying, hey, i know how to do that.
01:00
It's not going to work.
01:01
You have to know why the table works.
01:03
Works.
01:04
So you got to practice.
01:06
I'm not just ask for us to give you the answer.
01:08
So i'm going to walk through this again.
01:12
So we've got 20 volts.
01:13
We've got two oom resistors and then we know those.
01:17
Now the first step that we have is this column right here, six plus two plus four, the solid series.
01:24
So we can say that the overall currents are not but total resistance is 12 oms.
01:38
Now the other thing that we need here, because we're being asked to find this mystery total voltage.
01:45
So we don't have to find everything this time.
01:47
We just gotta find this mystery pieces.
01:54
So the current flow can be found right here.
01:57
So remember, oams law is voltage divided by resistance.
02:02
So the current flow here is 10.
02:04
So that must be the current flow throughout the circuit because it is a series circuit and due to the conservation of charge, all parts of the ceriscict must get the same current flow.
02:21
So here's all the mystery pieces for question a.
02:26
Now, why do i get these numbers? it's all about oms law.
02:32
So once we found the current flow, we knew all of the current flow for every device.
02:38
To find the independent voltages, it's just i times r.
02:42
So 10 times 6 is 60, 10 times 2 is 20, 10 times 4 is 40, 10 times 12 is 120.
02:50
And then 60 plus 20 plus 40 gives us 20 or 120.
02:56
So voltage, these are your answers for each of those devices.
03:03
Current flow is 10 amps, and then we've got our oms over here for resistance.
03:10
So that's how to solve number, our letter a, so let's try letter b.
03:14
I'm going to just use the same chart here because i don't have a lot of space to do all of these.
03:21
So we'll erase out everything and start again here.
03:25
So we got r1, r2, r3 again, and we're on a 120 volt power supply.
03:32
So we'll leave that here as our total.
03:34
So they're giving us different information.
03:36
We're going to use the same method to solve for all of these.
03:40
So it's the exact same method each time.
03:44
Vir chart.
03:50
All right.
03:51
So let's start drawing this in.
03:54
So on letter b, we've got 120 volts.
03:59
On r1, we don't know anything.
04:03
We need the voltage.
04:06
We need the total resistance.
04:09
So r1, we're out of luck right now.
04:13
R2, we do do the voltage.
04:15
It's 10, but we still, we don't know anything else.
04:21
So that's missing also.
04:25
And then vr3, we've got 80.
04:34
And we don't know its voltage either or it's resistance.
05:01
Okay, so we don't need to fill out all of this.
05:04
I was trying to figure out what is this question asking.
05:08
We only need to figure out the voltage.
05:10
We don't need to figure out the rest of the table.
05:12
Because right now, we don't have enough information to find anything but the voltages.
05:16
So this is trying to talk about kirschhaus loop rule.
05:19
Or voltage law, which just says that every loop has to have on the total voltage is zero.
05:27
So notice how if we have our current flow coming this way, we've got a 120 positive negative terminal.
05:36
And then each of these resistors is basically subtracting away the total voltage until there's zero left.
05:45
So this whole loop has to have a total, the voltage has to basically be used up by the time.
05:50
Gets back to the current or to the battery.
05:53
Otherwise, it would build up all that and it blow up.
05:56
So it doesn't do that.
05:58
So it's got 80 and 10.
06:00
We need to figure out how much more is needed to get to 120.
06:04
So 120 minus 90...