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:3:57

Video transcript

when we start to study electricity we need to get an idea of what is current and what is voltage and in to earlier videos I talked about the idea of current and voltage current and voltage and what they meant and when we talked about current it's easiest to describe current when we talk about wires let's say we have a copper wire we talked about a copper wire and inside it was there is electrons in it and they have a negative charge we know they have a negative charge and if we put a voltage on them those electrons would move in some direction like that so if I put a plus voltage over here and a minus voltage over here the electrons are repelled by the minus voltage and they're attracted to the positive voltage that is called an electron current you so talking about current in terms of what's actually happening in inside a wire make some sense it's easier to understand current and that these electrons are moving around and whenever we talk about this we'll talk about it specifically that there's an electron current going on here now at the same time what I said in that video and I'll say again is the convention for describing current is this this is called the conventional current direction the convention we've had for hundreds of years is that current is the direction that a positive charge would move if there was a positive charge there so whenever we talk about current from now on it'll always be conventional current and in fact we don't even need to mention conventional anymore it's just current current is the direction that positive charges would move if we ever talk about electron current then we'll use the word electron current now as a reminder when we talked about voltage this was built up by analogy the analogy was to electrons rolling down a mountaintop so here's our mountain to remember this and I built a battery or another voltage source like this and we said that what a battery does is it pumps out energetic electrons and they go down a hill roll downhill and go back into the back into the positive terminal of the battery and when we design circuits what we do is we we put stuff in the way of this electron on his path and this is where we build our circuits so the the electron current is going in this direction here down the hill the conventional current direction or the current direction is this way so now I'm going to redraw my circuit in my battery I'm going to flip the battery around it until the positive terminal is on the top and I'll put my circuit over on the side over here like this there's my circuit that I just built let's connect those circuits up like that this is the plus side of the battery this is the minus side the plus side goes with the long bar and the minus side goes with the short bar there and the current direction here the conventional current direction or just plain current direction is in that direction out of the positive and back into the negative from now on this is what we mean by current and we know that the electrons are in here they're heading around this way like that but that's okay this is the this is the nomenclature for or conventional current or just plain current