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Current time:0:00Total duration:3:57

Video transcript

- [Voiceover] When we start to study electricity, we need to get an idea of what is Current and what is Voltage and in two earlier videos, I talked about the idea of current and voltage, current and voltage and, 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 was 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. So talking about current in terms of what's actually happening inside a wire makes 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 any more, 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, uh, this was built up by analogy and the analogy was to electrons rolling down a mountaintop, so here's our mountain, 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 its 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 gonna redraw my circuit and my battery. I'm gonna 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 conventional current or just plain current.