 So in this video, we're going to look at the units of charge. And charge is measured in a unit called coulombs. A coulomb is a very large amount of charge, so normally when we deal with coulombs, instead we'll be dealing with micro-coulombs or nano-coulombs. So every electron has a very small amount of charge. It's actually 1.6 times 10 to the minus 19 coulombs. So for example, if I wanted to calculate the charge on one million electrons, I could do it like this. I take the charge on one electron and then multiply that by a million. And that gives me 1.6 times 10 to the minus 13 coulombs. So to go the other way, to find the number of electrons that make up a charge, instead you'd need to divide by 1.6 times 10 to the minus 19 coulombs. So for example, if I wanted to know how many electrons were in one coulomb of charge, it would be one coulomb divided by the amount of charge on each electron, which if I put that into my calculator, gives me 6.25 times 10 to the 18 electrons. That is an absolutely enormous number of electrons. That's actually about equal to the number of grains of sand that are on the earth. So it's a lot of electrons to just make up one coulomb of charge.