If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains ***.kastatic.org** and ***.kasandbox.org** are unblocked.

Main content

Current time:0:00Total duration:8:03

in this video we're going to talk about some terminology that we use to talk about how circuits are put together in previous videos we've talked about the components or elements that are used to make up circuits so for example resistor capacitor and inductor our circuit components we also call those elements in addition we have some sources like a voltage source or for example a current source those would be the components or elements of a circuit LM mints now we're going to start assembling these things into circuits and we need a few more words to talk about here's some circuit components that are laying out on the tabletop and we're going to connect those up with a wire so for example I could connect this one to this one with this yellow ideal wire and an ideal wire has zero resistance and it's perfect everywhere and this forms a junction between these two components and that is called a node node is the word for junction meaning the same thing that's what it that's what it notice if I connect up these two other components I still have one node because I have one junction that's the same voltage everywhere so that's what a node is we're going to go over to this circuit here and we'll identify the nodes this is a little more normal-looking tiny circuit here's a junction right here between a resistor and this voltage source so that's one node if I move over here I see resistors connected together by ideal wires so that forms one single node like that so that's our second node and down below same sort of thing I see the an ideal wire connecting the resistors and the source so I can color that in and that's node number three so this circuit has three nodes now what's connecting the nodes the thing that's connecting the nodes is called a branch and a branch is the same thing as an element well count the the branches or elements in this thing this voltage source connects the third node to the first node so that's one element this resistor connects node 1 and node 2 so that's the second branch this resistor connects node 2 and node 3 so there's the third branch and this resistor with a separate current also connects those two nodes so that's the fourth branch so this this circuit has 1 2 3 4 elements in it and it also means it has 4 branches 4 branches so that's what a branch in a node are I would move the picture over a little bit so that we can do this again on a little more fancy circuit so first thing we're going to do again just to repeat the process we're going to count the nodes here's a junction between a resistor and a source here's three resistors connected by a perfect wire so that's the second node here we find three more resistors connected by a perfect wire there's third down here we have there's a junction between two resistors so that's our fourth node and finally we have this node here connecting these four elements with one node this is sometimes called a distributed a distributed node when it's all spread out on the page like that but it's still just one node so this circuit has five nodes and if we count up the elements that tell us how many branches there are one element two three four five six seven seven elements alright there's our two two keywords elements and nodes now I'm going to quickly move again down bring in another circuit here we're going to talk about the idea of a mesh and the other thing we're going to talk about is the word loop the word mass comes from screen doors or screens that you put on on your windows to keep the bugs out if I draw a screen like this this is what it it looks like bunch of crossing wires and this little space right here that little gap is called a mesh that's what that word comes from so we're going to find the meshes of our circuit and what we look for here's the branches and the mesh is a it is a kind of a loop that fills up this open space this circuit has one mesh two mesh three meshes that's how that looks to draw a mess you start on a node you go through elements until you come back to where you started that's how we did those three and they fill the open windows of the circuit so this circuit has three meshes now that a mesh is a loop and we can have other kinds of loops too they don't have to be just the ones that fill the fill the windows so in general this circuit has other loops and we'll identify some of those we start let's just start at one of these nodes here and go around like that and this is a loop and I could draw their loops in here we'll make them all different colors there's a loop if I start right here I can draw a loop through these elements and finally if I have a sharp eye there's one more loop in this circuit if I start let's just start right here and it actually goes all the way around the outside so that's this circuit has three actually if I add them together this has three loops that I drew here plus the three loops that were the messers so this circuit has six loops circuits always have a lot of loops and so usually we don't talk about these more often it's more organized and straightforward to talk about how many meshes are in a circuit alright so that does it for this video we got mesh and loop we talked about components and elements and we finished up with the idea also of nodes and branches so that'll do it there's our new vocabulary for talking about circuits