All right, so this is the final video in our little series about the basic electrical circuit and it's inspired by the trip I'm taking to Haiti, where I'm going to be teaching young people about electrical basics, to hopefully inspire them to get into the trades or consider A trade education help the progress of their country and their own lives, and I want to show you the way that we describe this in the book. We talk about switches as being like a police officer who directs traffic, tells you when to stop. Tells you when to go and tells you to go in different directions and they also show a switch. The open and closing of a switch.

A closed switch is like a closed drawbridge where the electrons or cars can go across and when the drawbridge opens, the electrons can't travel across. So we're going to show a couple of the terms that are actually very simple but are easily confused both on schematics and then also in reality. So this would be a single pole, single throw switch. So, as the pole is the part that moves - and you can remember it's a pole because it looks like a pole and however many places it connects to - it - can either be a single pole, single, throw where it can only throw in one direction.

And then it's just open the other direction or it can be a double throw, which means that it can connect in either direction. Now this is actually a double pole, because you have two poles double throw because you have a throw in each direction. This would be a double pole: double throw switch so you'll see that on different relays or boxes or whatever we will say spst. That would be single pole single, throw dp/dt that would be double pole, double throw or even a single pole double throw which would be SP, DT.

So very simple, that's of those that are connected. Now you look at a contactor. This is a two pole contactor. So you have two and we know that we say that all times is a two pole.

Contact or the poles are the parts that move, but it's still only a single throw because it only opens or closes. So this is a double pole. Single throw contactor in this one is quite quite murder, not by the looks of it, and then we've got a 9340 relay, which I talk about all the time, and this is an example of a double pole, double throw. So this is very much like this.

In fact, it's very much even laid out the same way, so you can see this little diagram on the 9340, which makes it really nice you've got a normally closed connection between these two points and a normally open connection between these two points. So it's very much like this switch only in the case of this switch, it's manually moved from one side to another and there's not like a normally open or normally closed. It can be closed between these two open to both or close to these two and open to the other side. So you have this sort of manual control, whereas with a 9340 relay you are opening and closing alternately based on whether or not you energize this electromagnet.

I've showed this in other videos as well, but it's a really good basic understanding of what's going on, and so with. This relay being normally closed. Right now there's a connection between this point and this point and this point and this point and if we energize it, then it will switch and that will go open from here to here and go closed here to here and just a show very quickly with a Meter here we can show that we've got a closed path, so there we've confirmed that that we've got a path and then, if we go between these normally closed contact points, you'll hear it beep and then to whom this one. And this one same thing and you can see that very easily with that little diagram right on the face of it that these are normally closed.

That's that symbol there, and if we were to energize it, then those would go open and now these normally open ones would go closed. So that's it single pole, single, throw double pole, double, throw double pole, single, throw and then another double pole. Double throw the difference between these and these being. These are manually activated these types of switches and these are activated using electromagnets.

So there you have it. Hopefully that's helpful, we'll talk to you again next time.