 Now, let's practice a little bit with how to determine the direction of the current. I had a few videos that I had links to made by other professors that talked a little bit about conventional current versus electron flow, and I encourage you to watch those, but let's actually do some practice with it. So we've got this equation here for current, which really is just telling us how much current we have, because we've got charge and we've got time but we haven't indicated direction yet. For something which flows in a particular direction, you're going to have the amount of current and the direction of current. Really what that means is that current is actually a vector, and having vector quantities, you can represent them either with arrows, which is what we're going to do first, or using vector notation. So we're going to start out here by actually just indicating whether or not we've got positive or negative charge with the words. Then we're going to use thin blue lines to give us the direction of motion of those positive or negative charges. And finally, we will indicate the direction of the current using some thick red lines. That way, even if you're watching on a device that doesn't show you the color really well, you can see what it is we're dealing with. So let's start here with a case where I've got a positive charge moving towards the right. Well, conventional current is in the direction that the charges actually move, the positive charges. And so my current would also be listed as towards the right. Similarly, if I had a positive charge, I'm just going to copy this down here for a minute, but the positive charge was moving towards the left, then the current flow would move towards the left. Because the direction of positive charge motion and the direction of the conventional current are always in the same direction as each other. So if I've got a negative charge and it's moving towards the right, well the conventional current is actually going to be pointing in the opposite direction. So even though the flow of electrons is towards the right, we would define the direction of the current as being towards the left. And similarly, if we've got a negative charge moving towards the left, the conventional current would be moving towards the right. Because whatever direction the negative charges are moving, the conventional current is going to be opposite of that. Now that's expressing it in terms of arrows. And that's probably enough for most of you to be able to understand what you need to do on that. I'm going to go ahead and put up some vector notation here. If your class isn't using vector notation because you're watching this for a different professor, you can probably ignore the rest of this. On vector notation, this case that we have right here says that my charge is positive and I'm moving in the positive i hat direction. And when you multiply a positive and positive, you get a positive i hat and positive i hat is towards the right. If I had this case down here, I've got a positive charge but it's moving in the negative i hat direction. And so the net current flow is in the negative direction. My other two examples could be written out here in vector notation by noticing that I have a negative charge but it's moving in the positive direction. Remember the motion was the blue arrow. But this tells me the negative and the positive I'm going to have an overall negative direction for my current. And my last case here, I've got a negative charge moving in the negative direction. Again that's my blue arrow. But the negative and the negative multiply to give me out something in the positive direction which is why my current points towards the right. So you can think of it in terms of the arrows or you can think about it multiplying out the vector notation. But remember that positive charges, that's the direction of the conventional current. For a negative charge, the conventional current is going to go in the opposite direction.