 Now we're ready to look at a full loop example for Kirchhoff's Voltage Rule. And I'm going to start with a circuit here that's a little bit simple, but might have some things you're not quite used to in it. So I've got a symbol for a battery here. I've got one, two resistors. And then I've got a symbol over here, which I haven't shown in my class yet, but which is the ground symbol. Now that ground symbol just means that that particular point is set at being zero volts. In other diagrams it might just tell you exactly which point is zero volts. Now ultimately I want to find out what's happening with the voltage all the way around this circuit. And I'm going to start by actually making a line here showing the direction of my current. Because of the direction of the battery, and there's only one battery in the circuit, it's reasonable to assume that my current is going to flow around the circuit in this direction. That's going to let me know which direction it's going through each resistor so I can figure out whether there's a voltage drop or a voltage gain as I analyze my circuit. And I'm going to analyze my circuit going in the same direction as the current here. Now going back to some of my earlier videos, I can start labeling different points here. So for example on the battery you're always going to have a higher potential on the top side and a lower potential down here on the negative side of the battery. Similarly, when I look at the resistors, if you go back and watch those videos, the potential drops over a resistor. So I'm going to have a higher value and then a lower value. And a higher value and a lower value as I go around. Now as I finish this video, I'm going to take off some of this so it's not quite as such a mess as we're going through. Now symbolically, I can start to write this out because as I move around the circle, I'm going to start with a potential increase as I move across the battery from the lower to the higher side. But then when I move across the resistor, it's going to be a drop because I'm going to have a potential going from the higher side to the lower side. And how much is going to drop is going to depend on the current times the resistance. Similarly for the second resistor, I'm also going to have a drop in potential and it's going to be equal to the current times the resistance. And what Kirchoff's rule says is that in the end, all of the drops and the increases have to balance out to be back to zero. Now it's not zero because I started at zero volts. It's just as I increase and decrease, the amounts of increases and decreases have to balance out. If this was at a different potential, you would see that I still have to follow this if I look at the increases and decreases. So in order to start working with the equation, the first thing I'm going to have to do is I've got to figure out what is my value for the current. And for that, I'm going to be using Ohm's law because the current is equal to the voltage divided by the resistance. Remember the voltage is going to be the current times the resistance. I use that down here. So for our particular circuit, it's going to be the equivalent resistance I need and that equivalent resistance is the sum of the two values. And so that sum of the two Ohms and four Ohms gives me six Ohms and when I plug in my voltage of my battery, that's going to tell me that my current is 0.25 amps. Once I've got that, then I can actually start to figure out the voltage drop over each resistor. And I see for my very first one, it's 0.25 amps times two Ohms and then 0.25 amps times four Ohms. So that lets me know that here I'm going to have a drop of 0.5 volts and here I'm going to have a drop of 1.0 volts. So I'm going to start to clear up a few things here on my chart just to make sure that we've got our information all in here and pull out some individual pieces of information. So I know that I went from lower to higher and I started at zero volts and I have to increase by 1.5 volts, which means I'm going to have a value here of 1.5 volts. Now I'm going to drop and the amount I'm going to drop as I go from the higher side to the lower side is the value I calculated here, the current times the resistance, which is 0.5 volts, which means when I get here, it's got to go from 1.5 minus 0.5, which gives me 1.0 volts because that's a drop of 0.5 volts as I went over that resistor. And now I'm going to drop even further and I can figure out my potential at this corner because now I've got to drop 1.0 volts. So in this particular case, that dropping of basically 1.0 volts minus 1.0 volts is going to give me a value of 0 volts. Now that makes sense because between here and here, there was nothing to change the potential. If I had had another resistor here, then the individual drops would have been smaller. I would have dropped part here, part here, part there. The battery pumps it up, drops part, part, part. The battery pumps it up, it drops a little bit, a little bit, and a little bit, but it always comes back to the same value. Now again, as you're working through this, it can get a little bit confusing. And that's why I've tried to break this down into several videos showing you what happens over batteries, what happens over resistors, before we put it into a full loop where you were then able to find out what was happening to the potential all the way around the loop.