 Hello, my name is Lachlan McGinnis and I'm a departmental visitor here at the ANU as well as an excited particle, a science performer at CuestaCon and I'm a high school teacher here in Canberra. And what I'm going to be talking to you guys about is one of my favorite topics in physics, electrical circuits. And what I love about electrical circuits is how easily we can apply them to everyday life. Example, every day I use my phone, heaters, lights, kettles, computers and all these devices are powered by electrical circuits. Power is brought to buildings using extremely high voltage power lines at hundreds of thousands of volts. Power lines allow electrical energy to be transferred over hundreds of kilometers. This voltage is then decreased or transformed by one of these transformers when it reaches your house or office. So there's only 240 volts at the power points where we plug in our appliances. So batteries can also be used to power circuits. So every battery contains two terminals, a positive terminal and a negative terminal. Of this battery here, a positive terminal and a negative terminal. And what happens is when you connect an electrical component to the two terminals of the battery, electrical energy is transferred from the battery to the component and transformed or converted into a form of useful energy. These circuits allow electrical energy in the battery to be transformed into sound energy, light energy, heat energy and also kinetic energy, which we call motion. Please note that the energy in a battery is not used up, it doesn't just disappear. Instead, it is changed from one form of energy, electrical energy into another useful form such as light energy, heat energy or sound energy. And this is the basis of how circuits work. So welcome to this part of the course, electrical circuits.