0:00:00.060,0:00:01.859
On the bottom because I can[br]see that you couldn't see it.

0:00:02.890,0:00:07.480
Okay, when we first started this[br]problem we were given Vs Is and that

0:00:07.480,0:00:12.950
the resistances and we were asked to find[br]all of the currents which we just did.

0:00:12.950,0:00:16.950
Now we'd like to be able to find[br]the power from this particular source.

0:00:16.950,0:00:18.610
Well, how do I find power?

0:00:18.610,0:00:23.130
Let me look in my toolbox of[br]possible equations to use.

0:00:23.130,0:00:25.190
Here we used Kirchoff's Law.

0:00:25.190,0:00:29.960
And here is how we, and[br]this is how we calculate power.

0:00:29.960,0:00:34.310
So when I had Kirchhoff's Law I[br]knew my current source and

0:00:34.310,0:00:38.440
my voltage source and my resistance and[br]I was able to calculate current.

0:00:38.440,0:00:42.390
Now, if I want power,[br]I need to have one of these three things.

0:00:42.390,0:00:45.020
I need to have voltage[br]difference in the current, or

0:00:45.020,0:00:48.520
voltage difference in resistance,[br]or current in resistance.

0:00:48.520,0:00:52.840
Here I have,[br]can I have voltage difference and current?

0:00:52.840,0:00:57.130
I certainly have current, I've got I but[br]I don't have voltage difference.

0:00:57.130,0:00:59.450
So how can I get voltage difference?

0:00:59.450,0:01:02.210
Well, there are several tools that I[br]have for getting voltage difference.

0:01:02.210,0:01:04.540
And this is actually the one[br]that I'm going to use.

0:01:04.540,0:01:07.880
If I have, oops, is that the one I want?

0:01:07.880,0:01:11.900
Sure, voltage difference is[br]current times resistance.

0:01:11.900,0:01:14.180
So I have current, and I have resistance.

0:01:14.180,0:01:17.440
Right here I have current and resistance,[br]so I can get voltage difference.

0:01:17.440,0:01:20.180
So watch how I'm going[br]to solve this problem.

0:01:20.180,0:01:25.410
I'm going to use Kirchoff's Law with[br]my known sources to find current.

0:01:25.410,0:01:32.340
And then I'm going to use my current and[br]resistance to find voltage difference.

0:01:32.340,0:01:34.817
And then, kind of here in a line,

0:01:34.817,0:01:41.000
I'm going to use my voltage difference and[br]my resistance to find power.

0:01:41.000,0:01:42.550
So let's see how we do that.

0:01:46.083,0:01:46.855
Let's flip this over.

0:01:48.512,0:01:53.500
Okay, now I know I one,[br]two, three, and IX.

0:01:53.500,0:01:55.250
I also know my resistances.

0:01:55.250,0:01:56.770
So the next thing I'm going to do.

0:01:56.770,0:01:59.340
Remember I use my[br]Kirchoff's Law to get those.

0:01:59.340,0:02:02.670
Now I'm going to use Ohm's Law to[br]find the voltage difference, and

0:02:02.670,0:02:05.790
the voltage difference[br]is going to be V3 here.

0:02:05.790,0:02:09.720
So V3 is going to be I3 times R3.

0:02:10.810,0:02:15.890
That's the same voltage difference[br]that is across this current source, so

0:02:15.890,0:02:22.730
if I had V current source, let's call[br]it VS2, that would be equal to V3.

0:02:24.340,0:02:28.170
Now, I've used my Kirchoff's Law[br]to find my current.

0:02:28.170,0:02:31.240
I've used my Ohm's Law to[br]find my voltage difference.

0:02:31.240,0:02:35.510
And now, I want to use my Power[br]equation in order to find the power.

0:02:35.510,0:02:40.761
So, the power is equal to VS2 times Is,

0:02:40.761,0:02:45.245
which is equal to I3R3 times Is.