 In this video, we're going to be using the turns ratio that we can determine using the voltage here instead of turns. We don't have the turns that we've had in other videos, but we have the voltage here to determine what the current is through each winding, and it doesn't matter if we're talking about the secondary winding or the primary winding. So the first thing we're going to do when we get started is we're going to determine what the turns ratio is, and we do that by taking 1200 volts divided by 240 volts to get our turns ratio. Again, it is always the higher number divided by the lower number to get the turns ratio. In this case, it's a 5 to 1 ratio. Next up, what we're going to do is we're going to assign a voltage at the source here. So it is rated 1200 volts to 240, but that doesn't necessarily mean that we're putting 1200. It just means that the maximum voltage that we can handle here is 1200 volts. In this instance, however, we will add 1200 volts to the source. So we have 1200 volts at the source. With a 5 to 1 ratio, 1200 divided by 5 will give me the secondary voltage here, which in this case is 240 volts. Next up, we'll be adding resistance. So in this case, I'm just going to assign the resistance to be 16 ohms. So we can determine the secondary current at this point by taking 240 volts divided by 16 ohms to get my secondary current, which in this case is going to be 15 amps. Now this is where we can start using the turns ratio. So we have 15 amps on the secondary and we have 240 volts on the secondary. We have 1200 amps on the primary. We need to remember that lower voltage means higher current. Higher voltage means lower current. So when we use this turns ratio, we've got the higher current here. We're going to go 15 amps divided by 5 to get our primary current, which in this case works out to be 3 amps. So that's using the turns ratio. Now I find that using the turns ratio for current can be a bit confusing sometimes because we get so used to stepping the voltage down that we forget sometimes that we have to take the current and if we've got a higher voltage here, we end up with a lower current. So that can get a little confusing when using ratios. The way I like to work out these is taking that extra step and using the idea that our VAN is equal to our VAN out and what I mean by that is the power that this side uses is the power that this side has to give. So if I have 240 volts here with 15 amps, I can determine the power by taking 240 times 15 amps to get the power that this side is using and whatever the power this side uses, this side has to give. So that is the idea of VAN equals VAN out. VAN equals VAN out. It's one of the primary rules of transformers along with the volts per turns primary equals volts per turns secondary, whatever the output of the power is of the transformer has got to equal the input of the power of the transformer. So going back to our original example, 240 volts divided by 16 amps, ohm sorry gives us 15 amps, 240 volts times 15 amps will give us 3600 VA. If we have 3600 VA on the secondary, that means we have to have 3600 VA on the primary. Now that we've determined that we have 3600 VA on the primary, we take 3600 VA divided by 1200 volts and get our primary current. In this case, that equals three amps, which is what we worked out before when we used the turns ratio. I know it seems like there's an extra step involved, but I just find it way easier to deal with the VAN VA out rule than trying to remember that I might have to step up or step down my current depending if it's a step up or step down transformer. So again, VAN equals VA out will get you the right answer all of the time and you don't have to confuse yourself so much with the turns ratio and the current.