 Let's explore electric current and circuit. A circuit consists of wires that have electrons, negatively charged electrons everywhere, which I have shown in yellow color over here. It has a power source like a battery. Its job is to push and pull on the electrons. The positive terminal pulls the negatively charged electrons and the negative terminal pushes on them. But the electrons are not moving right now because the circuit is not closed. That's where the switch comes in. When I close the switch, the circuit becomes complete and then the electrons can move. And when the battery transfers energy into the electrons making it move, the electrons then transfers energy into the appliance like a bulb. And that's basically how your electric circuit works. Now let's close the circuit and see what happens. Boom, there you go. Did you see that electrons start moving everywhere? Let's do that, let's look at it one more time. Boom. The electrons start moving everywhere and that's what we call an electric current. So the current in a circuit starts everywhere at the same time. Lastly, what's the direction of that current? It might look like the direction of the current is this way, but we define the direction of the current to be the opposite direction. Can you see? Opposite direction of the electrons moving. Why? Because electrons are negatively charged particles. We like to think about the direction of the current in the direction of positive charges. So if there are some positive charges moving, then the direction of the current would be the same direction. But for negative electrons, the direction of the current would be in the opposite direction. So you see electrons are actually being pushed from the negative terminal and being pulled back into the positive. But the direction of the current is from the positive side of the battery to the negative terminal of the battery. But now let's think about how do we calculate the current? The current flowing through any point will always be the amount of charge flowing through that point per second. And so the unit of this current would be coulomb, that's the unit of charge, per second. And coulombs per second is called ampere. Let's take a couple of examples. So for the first example, let's say we have charges moving from P to Q, let's say this way. And we find that there are about 10 coulombs of charges are flowing through this point, let's say, from P to Q in two seconds. What is the current? Well, the current over here is going to be the amount of charge, 10 coulombs, but they're flowing in two seconds. Two seconds per time, two seconds. And that gives me five coulombs per second, which is five ampere. Notice I'm not saying that there are five electrons are going per second. No, the charge on an electron is very tiny. So there are billions and billions of electrons flowing, but total 10 coulomb worth of electrons are flowing in two seconds. So five coulombs per second, that gives me five amperes. What is the direction of this current? Is it from P to Q or Q to P? Well, remember, direction of the current is in the opposite direction of the flow of electrons. So the current is this way, Q to P. All right, let's take a second example and I want you to try this now. Imagine I tell you that there is a current. At this time, I give you the current, let's say, and current of two amperes, okay? And let's imagine we observed this for 10 seconds. We want to calculate how many charges are flowing through this point in 10 seconds. Can you pause and figure this out yourself first? All right, let's see. I know that current is charge per second. This time, I'm given the current and I'm given the time. I have to calculate what Q is. So from this, what will Q be equal to? Well, Q will be equal to I multiplied by T. And so Q will be equal to two amperes multiplied by the time, which is 10, and that will be 20 coulombs. So 20 coulombs of charge is flowing through this point. If these are electrons, what direction are the electrons flowing? Well, if these are electrons, they will be flowing in the opposite direction. But if these were positive charges, hypothetically, then they would be flowing in the same direction.