 You have now been introduced to both voltage and current, two of the key ideas that underpin electricity. However, before we continue, I just wanted to spend one minute sharing with you guys two quotes, which I think are amazing. They're both from Michael Faraday, a man who lived in the 1800s and he played a key role in the development of electricity. So the first quote is this. So this is in 1850 before electricity was commonplace. And so a British financial minister came up to Michael Faraday and said, what use is this electricity? And Michael Faraday is responsible as, well, maybe one day you'll be able to tax it. At this stage, people had absolutely no idea what all this research into electricity could lead to and how could underpin all our technology today. The second quote, there's a shortened version that I'll share with you and it is simply nothing is too wonderful to be true. All right, that's enough with quotes for now. Let's get back to voltage and current. So current and voltage are two very important concepts when it comes to electrical circuits. And I want to share with you guys the way that I understand what they are. So for me, the key to understanding current and voltage is to look at the units of these two quantities. So let's start out by looking at amperes or current. So electrical current is represented by the symbol I. So that's capital I and its units are amperes. When ampere is a Coulomb per second. So an ampere is a Coulomb per second. And to help you understand how this works, I'm going to show you a simulation. So if we were to have a look at an actual circuit, so here I've got the circuit simulation that we're using before. So the current would be the number of Coulombs that go past a certain point in the circuit per second. So I was going to have a look at this part of the circuit right here. If one Coulomb of charge goes past every second, then I have one ampere of current. If I had the charges moving twice as fast, so I had two Coulombs of charge going past each second, then I would have a current of two amperes. So if I had more electrons moving through a certain point of the circuit, then I would have higher current. I'm now going to show you a formula that you can use to calculate electrical current. The formula is I equals Q over T, where I is the electrical current in amps, Q is the charge that flows through a point in the circuit measured in Coulombs, and T is the amount of time that is passed in seconds. So you can use this formula to calculate the current. Have a go at doing this now.