On the bottom because I can see that you couldn't see it.
Okay, when we first started this problem we were given Vs Is and that
the resistances and we were asked to find all of the currents which we just did.
Now we'd like to be able to find the power from this particular source.
Well, how do I find power?
Let me look in my toolbox of possible equations to use.
Here we used Kirchoff's Law.
And here is how we, and this is how we calculate power.
So when I had Kirchhoff's Law I knew my current source and
my voltage source and my resistance and I was able to calculate current.
Now, if I want power, I need to have one of these three things.
I need to have voltage difference in the current, or
voltage difference in resistance, or current in resistance.
Here I have, can I have voltage difference and current?
I certainly have current, I've got I but I don't have voltage difference.
So how can I get voltage difference?
Well, there are several tools that I have for getting voltage difference.
And this is actually the one that I'm going to use.
If I have, oops, is that the one I want?
Sure, voltage difference is current times resistance.
So I have current, and I have resistance.
Right here I have current and resistance, so I can get voltage difference.
So watch how I'm going to solve this problem.
I'm going to use Kirchoff's Law with my known sources to find current.
And then I'm going to use my current and resistance to find voltage difference.
And then, kind of here in a line,
I'm going to use my voltage difference and my resistance to find power.
So let's see how we do that.
Let's flip this over.
Okay, now I know I one, two, three, and IX.
I also know my resistances.
So the next thing I'm going to do.
Remember I use my Kirchoff's Law to get those.
Now I'm going to use Ohm's Law to find the voltage difference, and
the voltage difference is going to be V3 here.
So V3 is going to be I3 times R3.
That's the same voltage difference that is across this current source, so
if I had V current source, let's call it VS2, that would be equal to V3.
Now, I've used my Kirchoff's Law to find my current.
I've used my Ohm's Law to find my voltage difference.
And now, I want to use my Power equation in order to find the power.
So, the power is equal to VS2 times Is,
which is equal to I3R3 times Is.