Video: Energy transfers

﻿Hello, I'm Dr. Fishwick. And I'm one of the science teachers here at Oak National Academy. I'm going to be taking you through the key stage four physics topic of energy. We're going to be exploring the ideas of stores and transfers of energy, along with ways in which we can change energy within a system. And finally, we will eventually discuss global and national energy resources. But before we get started, can you please make sure that your area for working is distraction free and as quiet as possible. So that means turning the notifications off on your phone, turning it off completely if possible, closing any additional browser tabs and making sure that you're fully prepared to be as focused as possible for these lessons. For this lesson, you're going to need the following equipment. A pen and some paper, a ruler and a pencil and rubber to allow you to complete all the tasks. Please pause the lesson now, if you need to go and collect this. Today's lesson is the first lesson in the energy topic for key stage four physics. In this lesson, we're going to be looking at the main eight energy stores. We'll describe and define them. And then we will talk about pathways in which we can transfer energy. Following that, we will look at how we can describe those transfers to create a full description of an energy system. So, the title is at the top of the page, make sure you've got that written down. On the screen now, you can see a series of six different jobs that require a good understanding of energy sources, energy stores and transfers. I'm just going to let you look at them for a second. So you can see that there's quite a wide range, not just your traditional science based careers, such as the oil rig engineer. You can actually see that nutritionists or designers will need a good understanding of energy stores and transfers as well. So, let's begin with our lesson. When discussing energy stores in physics, we're specifically interested in stores on which we can perform calculations to understand what is happening in terms of transfers and where energy is currently being stored. It's important to know of these terms and how we might describe them. So out of the eight stores, we have a gravitational potential store, which can be filled by raising an object in a gravitational field. The kinetic store, which is filled by objects that have mass and are moving at a speed. The thermal store, which is filled by particles vibrating more as the temperature increases or during the change of state for a substance. A chemical store, which can be filled by molecules being pulled apart from each other. An electric magnetic store, which can be filled by charges being separated or due to the attraction and repulsion of magnets. So now we're up to the electric magnetic store. We also have a vibrational store, which can be filled when something vibrates more. So with a larger amplitude. We also have a nuclear store, which can be filled by combining small light nuclei into heavier nuclei. That's only really possible inside stars. And finally, we have an elastic potential store, which can be filled by stretching or compressing an object so it is no longer its natural size. There are several of these that we will be learning about over the next few lessons where we will perform calculations specifically attached to some formulae for them. And these are the gravitational potential, kinetic, the elastic potential, and we will be calculating parts of the thermal store. For now then, let's see what we understood. Which store is linked with stretching and compressing? In three, two, one, say your answer. That's correct, it is the elastic potential store. Which store is linked with the state or temperature of an object? In three, two, one. That's right, it is the thermal store. Which store is linked with the nuclei of atoms? In three, two, one. That's correct, it is the nuclear store. So, now that we've had some quick practise to check that we understood what was being said, I'd like you to pause the lesson now so that you can match all of the stores with their appropriate description. Do so by writing this out on your paper. And here are the answers. Please pause the lesson now so that you can mark them. Well done for the ones that you got correct. Any that you didn't get correct, it's now time for you to go and add any corrections. It's really important that we understand these stores, particularly the ones that we're going to be performing calculations on. These are really important to understanding general everyday actions. Physicists are interested in how energy is transferred when something happens. And we can write descriptions of these energy changes by thinking about the following things. Where is the energy at the start of the event? And where is the energy at the end of the event? In what way is it stored? And additionally, we can think about, by what method is the energy transferred between these stores? And we're going to look at different methods of transferring energy and then apply this to some different systems. So there are four ways of transferring energy. And we call these ways of transferring energy pathways. They are radiation, which just means energy given out or emitted from a source. And that can be light or sound for example. So that's radiation. Another pathway is the mechanical pathway, by which we transfer energy when a force does work on an object. It's causing it to move or change shape. Heating is a method of transferring energy by directly heating an object. And then there is the electrical pathway such as the transfers in electrical circuit, due to the charges moving. So to recap, we have radiation, mechanical, heating and electrical pathways. Now it's time to check our understanding again. There's going to be a few more of these quick questions to check what we've understood. So, on the count of three, I want you to answer which pathway involves forces doing work? In three, two, one That's right, it is the mechanical pathway. Which pathway involves lights or sounds? In three, two, one. That's right, it is radiation. Which pathway involves circuits? In three, two, one. That's correct, it is the electrical pathway. Which pathway involves changing temperature? In three, two, one. That's right. Well done, it is the heating pathway. Which pathway involves lights or sounds? In three, two, one. That's right, it is radiation. Which pathway involves circuits? Three, two, one. That's right, it is the electrical pathway. And which store was linked with the nuclei of atoms? Three, two. That's right, it is nuclear. Okay. We've reached a point where we've gone through and understood the different stores and the different pathways. What I would like you to do now is pause the lesson so that you can complete these questions. And here are the answers. Pause the lesson now so that you can mark them. When we describe transfers, we need to think about where energy is stored initially and where it is going to end up. If energy ends up in a store temporarily, then it might not always be useful to think to include it. For example, when a car on its journey starts with all the energy stored in the chemical store of the fuel and at its end point, the car has the energy stored in the thermal store of the car and the surroundings. It will, during that time have transferred energy to the kinetic store whilst it was moving. But as our start and end points have the car stopped, we don't need to consider the energy in the kinetic store. So, we're going to have a look at some of these descriptions and we're going to use stores and pathways to help us describe them. Let's think here about a bullet being fired into a block of wood. We have a before picture and an after picture. We can see that initially that bullet is moving. So it must have a filled kinetic store. But at the end it has stopped. And so that energy that was in the kinetic store, must have transferred somewhere. So when the bullet is travelling, it has a filled kinetic store because it is moving. When it hits the wood, the bullet does mechanical work on the wood, and that's going to transfer energy from the bullet's kinetic store to the thermal store of the wood, bullet and surroundings. So, kinetic, this one is clearly a store. So I'm going to highlight this with light blue. So the stores I'm going to box in light blue. Any place where we see an example of a pathway, I will box with the orange. So when it hits the wood, the bullet does mechanical work. So that is a pathway. This transfers energy from the bullet's kinetic store to the thermal store. So we can see here, we have the stores highlighted in blue and the way in which it was transferred, highlighted in orange. So it's really important that we understand where we're using stores and transfers in our descriptions. So for this example, I'd like you first to look at the picture, and then I want you to read the text that's on the screen and we're going to work through this one together. Okay, so when we look at this diagram, we can see that there is an archer pulling back on his bow. And to start with, all of that energy is going to be stored in the elastic store of the bow. When he releases that string, the arrow is fired from the bow. And all of the energy that was stored in the elastic store of the bow, is transferred to the arrow. And the arrow is moving, so it's in its kinetic store. So at first, when the archer is pulling on the bow string, what's being done? Well, mechanical work is causing energy to be transferred from the chemical store of the archer's muscles, to the elastic store of the bow. When the string is released, what's happening? Mechanical work is being done on the arrow. Then when the arrow is travelling through the air, the arrow has filled its kinetic store. So once again, our stores are being highlighted in blue. You had a chemical store in the muscles, elastic store of the bow and the kinetic store of the arrow. In all cases here, the pathway for energy transfer was mechanical work. Pause the lesson now, to add this to your notes. So, we've had a go together. You've seen me talk through an example. Now's the time to pause the lesson, so that you can complete some practise. Pause the lesson now so that you can complete this question. And here are the solutions. Pause the lesson if you need to spend longer identifying the stores and pathways. And here we have another problem for you. I would like you to identify the stores and pathways in this example. Pause the lesson now. And here are the solutions. Can you see that the three... We have two stores involved, one of them involved more than once. The chemical store and the gravitational store. But we have two pathways involved for the energy transfer. This time we have the electrical pathway within the motor and then mechanical work being done on the mass to raise it in the gravitational field. So far, we've spoken about how these changes occur and the use of pathways and stores model to discuss this. Once I talk through this next section, I really want you to make sure that you're not writing and that you're just focused on what I'm talking about. So, we've spoken about how the changes occur and using stores and pathways to model this. However, we're eventually going to need to consider how to calculate these changes. And to do that, we need to consider the quantitative values of what's stored within these different systems. We're not going to be performing calculations, but we need to be able to represent different quantities in different stores. Let's consider a pendulum moving between the two extremes of its positions. So let's start, with the pendulum on the far left of the screen. This has been pulled up to its maximum height. By raising it up, we will have added energy to its gravitational store, and this is the maximum height that it's going to reach. So in terms of quantities, it will have a maximum. Next, we release the pendulum and it begins to swing. In this direction towards the midpoint. And it will end up in the blue position here. When it's in that blue position, it's at its minimum height. So none of the energy that we added to the gravitational store will remain in that store. It's moving and it's actually moving at the maximum speed that it can have. So all of the energy will have transferred to the kinetic store. It continues to swing, passing in this direction. And on its way back up to its maximum height, we consider this point about halfway. We can see, in this perfect position that it's not at its maximum height, so the energy cannot be solely in the gravitational store. It's also not moving as fast as it was when it passed through the middle. So the energy cannot solely be in the kinetic store. It must be a combination. Here is a combination that represents where the energy is stored in this position. Not all in the gravitational store, not all in the kinetic store. What I would like you to do now, is pause the lesson to make a copy of these notes, to identify where the energy is stored for this system. Now that we've had a go at modelling an example, what I want you to do now is pause the video and I want you to describe the stores and transfers and represent each of the changes in a chart. Pause the lesson now, so you can complete this task. And once again, we have another task for you to complete. So pause the lesson now so that you can complete this task. Here are the solutions to the first question. Pause the lesson now so that you can mark it. In that intermediate state, whilst the candle is burning, some of the energy will be stored in the chemical store, still some is going to be in the thermal store of the surroundings. Not all of it will have transferred. You may have different values. You may have one in the chemical store and four in the thermal store. That doesn't matter. It's just as long as it's an intermediate stage. And here are the solutions to the second question. Please pause the video now so that you can mark your answers. So, in this situation we've started with all of the energy in the gravitational potential store to start with all being transferred to the elastic store at the bottom of the bungee jump. And finally, we have another example for you to try. So, a wind up car is going up a ramp. When it is wound up, a spring inside is stretched. When the spring is released, it causes the car to move. If you're ready to tackle this without any additional guidance, please pause the lesson now and begin. If you're not ready to tackle this without some more guidance, I'm now going to put up some images to help you. So we have the spring wound at the bottom, the car's travelling up the ramp and the car is stationary at the top. I'd like you to think about which stores of energy are filled in each of those three locations? Where is the energy most going to be stored? And therefore which stores are going to need to be involved? Think about for the car stationary at the top It's at the top of a ramp, what store is going to have its most at that point? That's right, it is the gravitational store. At the bottom of the ramp, what's that gravitational store going to be? Zero. And finally, of course, for that bottom position, the spring has been wound up. So that's stretching and compressing. So we're storing energy in the elastic store. That is correct. Okay. Pause the lesson now so that you can answer this question. And here are the solutions. Pause the lesson now so that you can mark your answers. Well done, if you correctly identified all the different stores involved. And if you identified that the pathways for transferring this energy were mechanical working. So that's the end of this first lesson in the topic. Today we've looked at the eight main stores of energy, the four different pathways for transferring energy and describing ways in which we can do these different transfers. All that remains is for you to go and complete the worksheet and exit quiz for this lesson. I look forward to seeing you in a future lesson.

Worksheet: Energy transfers

Exit Quiz: Energy transfers

Completed: Energy transfers

In this lesson we are going to explore the 8 stores of energy, and the 4 pathways in which energy can be transferred. This will provide an overview to allow the consideration of transfers in more complex systems.

Physics

Energy transfers

Video

Worksheet

Final Quiz

Lesson Complete