 So using these two rules I can make all sorts of predictions about circuits And in this case here, I'm going to use them to predict what the current is going to be through this circuit here So let's see. What do we know? I've got nine volts on this side So that means that at this point here, I must still have nine volts And at this point here, I'm at zero volts So as the charges move across these resistors here, they must lose nine volts of energy And I also know That the amount of current that's going into this resistor must be equal to the amount of current going out of this resistor Because of the node rule So I know the current through each of these resistors must be the same Let's put this into equations. I'm going to call this resistor resistor 1 and This resistor resistor 2 and I know that the voltage drop across Both resistors, so the voltage across resistor 1 Plus the voltage drop across resistor 2 must be equal to nine volts And I also know from Ohm's law that the voltage Across one of these resistors is going to be equal to the current times the resistance So in this case, I would have Then using conservation of charge or the node rule I know that the current going across resistor 1 must be equal to the current going across resistor 2 So i1 equals i2 So now I have a series of four equations I can use all these equations together to find the current that's flowing through the circuit So first of all, I'm going to substitute first of all, I'm going to substitute equation 2 into equation 3 into equation 1 So that will give me And now I'm going to substitute equation 4 to get rid of i1 So now I can rearrange this to solve for i2 And in this case, I know that both r1 and r2 are equal to One ohm each so that gives me Excuse me nine volts over two ohms which is equal to 4.5 amps So now I've worked out the amount of current that is flowing through this circuit