Universe. Learning outcomes. Credit value: 5

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1 Credit value: 5 2 Energy and our Universe Most of the appliances we use at home and at work use energy from sources that are running out. If we are not careful we won t have any energy to do the things that we take for granted. By understanding energy better, we can plan for the future by designing and building new technology that lets us derive energy from sources that will not run out. In this unit you will learn how energy is transferred and used along with the different sources of energy and how they can be used to generate electricity. You will investigate how we can make better use of the energy we use at home and in the workplace. You will also have the opportunity to carry out practical work, for example investigating how to minimise energy loss at home. You will also learn about different types of light and radiation and how they can be used in our everyday lives and in the world of work, such as the use of gamma radiation to treat cancer patients. Finally you will learn about the Universe and our place in it. You will have the opportunity to investigate the origin of the Universe and our Solar System and discover theories that astronomers have to explain how the Universe is changing. Learning outcomes After completing this unit, you should: 1 be able to investigate how various types of energy are transformed 2 know applications of waves and radiation 3 know how electrical power can be transferred for various uses 4 know the components of the Solar System and the way the Universe is changing.

2 BTEC s own resources Assessment and grading criteria This table shows you what you must do in order to achieve a pass, merit or distinction grade, and where you can find activities in this book to help you. To achieve a pass grade the evidence must show that the learner is able to: To achieve a merit grade the evidence must show that, in addition to the pass criteria, the learner is able to: To achieve a distinction grade the evidence must show that, in addition to the pass and merit criteria, the learner is able to: Carry out practical investigations that demonstrate how various types of energy can be transformed See Assessment activities 2.1, 2.2, 2.3 and 2.4 Describe the energy transformations and the efficiency of the transformation process in these investigations See Assessment activity 2.2 P1 M1 D1 P2 Calculate the efficiency of energy transformations See Assessment activity 2.5 Explain how energy losses due to energy transformations in the home or workplace can be minimised to reduce the impact on the environment See Assessment activity 2.4 P3 P4 P5 P6 P7 P8 P9 P10 Describe the electromagnetic spectrum See Assessment activity 2.6 Describe the different types of radiation, including non-ionising and ionising radiation See Assessment activity 2.8 Describe how waves can be used for communication See Assessment activity 2.7 Describe how electricity can be produced See Assessment activities 2.9, 2.10 and 2.11 Describe how electrical energy is transferred to the home or industry See Assessment activity 2.12 Describe the use of measuring instruments to check values predicted by Ohm s law in given electric circuits See Assessment activity 2.9 Describe the composition of the solar system See Assessment activity 2.13 Identify evidence that shows how the universe is changing See Assessment activity 2.14 M2 M3 M4 M5 M6 Describe the uses of ionising and non-ionising radiation in the home or workplace See Assessment activity 2.8 Explain the advantages of wireless communication See Assessment activity 2.7 Compare the efficiency of electricity generated from different sources See Assessment activities 2.11 and 2.12 Describe the main theory of how the universe was formed See Assessment activity 2.14 Explain how the evidence shows that the universe is changing See Assessment activity 2.14 D2 D3 D4 D5 D6 Discuss the possible negative effects of ionising and non-ionising radiation See Assessment activity 2.8 Compare wired and wireless communication systems See Assessment activity 2.7 Assess how to minimise energy losses when transmitting electricity and when converting it into other forms for consumer applications See Assessment activity 2.12 Evaluate the main theory of how the universe was formed See Assessment activity 2.14 Evaluate the evidence that shows how the universe is changing See Assessment activity

3 Unit 2 Energy and our Universe How you will be assessed Your assessment could be in the form of: presentations case studies practical tasks written assignments. Tariq, 18 years old I enjoyed this unit and I particularly liked the section on the Solar System as looking at the night sky fascinates me. It is amazing how we can see objects that are millions of miles away from us. Our class took a trip to the National Space Centre, in Leicester, which was fantastic and it brought this unit together. I found the section on using light in communication very useful as it showed me that there are lots of technologies, some better than others. We experimented with laser light, which I found really interesting. Energy issues are always on the news and the section on energy allowed me to be part of this debate. I feel that completing this unit has improved my practical skills and made me more aware of the world we live in. Have you got the energy? Imagine our lives without energy. How could we work without eating or drinking? How could a bus move from one bus stop to another without the fuel its engine needs? How could your mp3 player work without the electrical energy it requires to power it up? In small groups discuss some other things you have used recently that require energy. In your groups work out what type of energy has been used. Catalyst 37

4 BTEC s own resources 2.1 Understanding types of energy In this section: P1 Types of energy Energy is vital to everyday life and we use it to do all sorts of things. The table below shows some examples of different types of energy. Type of energy What is it? Example Potential (e.g. elastic, gravitational, chemical) Stored energy that has the potential of doing work Kinetic Movement energy Sound energy is used to test metals in the aerospace and automotive industries. Cracks, or weak areas, reflect the energy. Light (electromagnetic) Bright objects give out light energy Sound Things that vibrate give off sound energy Thermal (heat) Energy that is transferred from a hot region to a cold region Grading tip P1 Part of meeting the criteria is to list types of energy. When doing your assignment, make sure you give all the different types of energy given in the table. Electrical Flow of charge in an electric circuit 38

5 Unit 2 Energy and our Universe Energy transformations We need energy to do all sorts of things. Running, reading and even sleeping require energy. Energy can be transformed (changed) from one form to another. Anything that takes in energy must also give out energy. Here are some examples. A girl running gets her energy from the food she eats. The energy is then transformed to movement (kinetic energy), sound and heat energy. The light bulb that lights your room gets its energy from electricity. The energy is then transformed to light and heat energy. Remember: don t touch a lit bulb it will burn. Activity A Write down three ways in which you have experienced energy being transformed today. Using energy at home and in the workplace We use many different appliances at home and at work that convert energy from one form into others. Activity B For each thing pictured on the right, write down the type of energy that is going into it and the types of energy that it is giving out. (Hint: remember that most things give out more than one form of energy.) Energy transformations are all around us. Assessment activity 2.1 P1 You are a food scientist working for a supermarket, looking at energy in food. 1 Find out how much energy is stored in a can of drink (any type). This value will be marked clearly on the label. P1 2 What form of energy is in this drink? P1 3 Investigate what happens to this drink as it goes into your body. P1 Grading tip Remember, everything requires energy even sleep! This means that you should be able to find enough types of energy to cover the content for P1. PLTS When you carry out your investigation you will be learning to enquire independently as well as developing your self-management skills. 39

6 BTEC s own resources 2.2 Describing energy In this section: Key terms P1 Energy block diagram shows the forms of energy going into and out of a system. M1 Sankey diagram shows how much energy is going into and out of a system. Conservation of energy tells us that energy is transformed to various forms and is not destroyed. When engineers and designers create the appliances we use in everyday life they need to know how much energy is transformed to useful forms and how much is wasted. They can then improve their designs by trying to reduce the amount of wasted energy. For instance, we now have more efficient energy-saving light bulbs in our homes. Case study: Energy-efficient flight Jenny is a trainee engineer working for an aerospace company. She is working with other engineers to design a more efficient engine for the planes. They want the engine to transform as much energy as possible into useful forms and to reduce the amount of energy that is wasted. Which types of energy given out by the engine are wasted? Engineers design aeroplanes to be as energy efficient as possible. Investigating energy You need to be able to describe energy changes that take place in everyday situations. It is helpful to break the problem down. This example shows you how you could do this: Consider a ball on a work bench. What kind of energy does the ball have? (Hint: what energy is related to having the potential to do something?) Now consider what happens as the ball falls. What energy is being transformed? (Hint: which energy is related to motion?) As the ball hits the ground and then rebounds, does it reach the height it fell from? Explain your answer in terms of how energy is transformed. Tracking transformations We use energy block diagrams to understand how energy is transformed. This block diagram shows the energy transfers that occur in a moving lorry. Chemical energy from burning fuel Electrical energy used for radio, lights, recharging battery etc. Kinetic energy used to move the lorry Wasted thermal (heat) and sound energy 40 An energy block diagram showing the energy transfers that occur in a moving lorry.

7 Unit 2 Energy and our Universe The block diagram shows you that the lorry is powered by chemical energy in the form of fuel. The chemical energy is transformed into: kinetic energy that moves the lorry electrical energy that powers the lights, radio, recharges the battery etc. sound energy thermal (heat) energy. The heat and sound energy are transferred to the surroundings as wasted energy. Activity A Draw a block diagram to show the energy transformations for someone using a hairdryer. (Hint: energy comes out of the hair dryer in more than one form.) Useful versus wasteful energy It is useful to know how much energy is actually transferred into useful energy and how much into wasteful energy. You can show this by constructing a different type of block diagram called a Sankey diagram. A Sankey diagram for the moving lorry is shown on the right. In a Sankey diagram the energy flow is shown by arrows. Broad arrows show large energy transfers. Narrow arrows indicate small energy transfers. We say that the width of the arrow is proportional to the energy. The total amount of energy that comes out of the lorry is equal to the total amount of energy that goes in. We say that the energy is conserved. Physicists call this the law of conservation of energy. Assessment activity 2.2 P1 Electrical energy used for radio, lights, recharging battery etc J Chemical energy from burning fuel J M1 Wasted thermal (heat) and sound energy J Kinetic energy used to move the lorry J A Sankey diagram showing the size of the energy transfers for a moving lorry. You are working for a leading IT company. Your manager wants you to look into energy-efficient computers. To start, you investigate the energy used by one of the company s existing computers. 1 State in words the types of energy involved when the computer is in use. P1 2 Draw a block diagram to show the energy transformations. M J of electrical energy is supplied to the computer. In the process 65 J is used to generate light energy, 190 J is transformed into thermal (heat) energy and 95 J is transformed into sound energy. Draw a Sankey diagram to show the energy transfers. M1 Grading tip Remember that when you draw a Sankey diagram, the amount of energy leaving the system must be the same as the energy that enters it. 41

8 BTEC s own resources 2.3 Understanding thermal energy In this section: Key terms P1 Free electrons electrons within the atom of a metal that are shielded from the nucleus and are free to move. Density the amount of matter that occupies a specific volume; something heavy that takes up a small space has a higher density than something that weighs the same but takes up more space. When you touch a metal gate on a winter morning it feels cold. This is because the thermal (heat) energy from your hand is being transferred to the metal. Scientists need to understand how thermal energy is transferred so that they can design useful products. For example, a vacuum flask is used to keep liquids hot (or cold) by preventing heat transfer. Saucepans are made out of stainless steel so that they transfer heat quickly from the cooker to the food inside the pan. Thermal energy can be transferred in three ways: conduction, convection and radiation. Conduction You know that all substances consist of atoms. In a solid, the atoms are close together; in a liquid, the atoms are more spread out; and in a gas, they are very far apart. Unit 1: Page 6 shows the structures of solids, liquids and gases. The atoms in substances vibrate. When a substance is heated, its atoms vibrate more. If one end of a metal bar is heated, the other end eventually gets hot. You may have noticed this if you ve used a metal spoon in a saucepan. This is because the heat is transferred from atom to atom through vibrations; this is called conduction. Solids conduct thermal energy better than liquids or gases because the atoms are closer together in solids. Metals are the best conductors of heat because they also have free electrons that transfer thermal energy. free electrons Vacuum flasks keep liquids hot by minimising heat loss due to conduction, convection and radiation. HEAT A non-metal transfers heat through the vibration of its atoms. These are poor conductors of heat but good insulators. HEAT A metal transfers heat through the movement of free electrons as well as through the vibration of its atoms. 42

9 Unit 2 Energy and our Universe Activity A Imagine heating up some baked beans in a metal saucepan. You stir the beans with a metal spoon. Using the idea of conduction, explain why the spoon gets hot. Convection The atoms in liquids and gases are free to move around because they are joined by only weak forces. Thermal energy can be transferred because of the movement of these atoms. This is called convection. Convection allows a radiator to heat a whole room rather than just the air immediately surrounding it. This is shown in the diagram on the right. Activity B Now imagine heating up some soup. Even if you don t stir it the whole pan of soup eventually heats up. Use the idea of convection to explain why. The warm air is less dense so rises The radiator heats the air surrounding it As the air cools down it becomes more dense and sinks Cool air moves in to replace the warm air This room is being heated by a radiator; the convection current is shown by arrows. Radiation Radiation is the third way of transferring thermal energy. The heat is transferred by infrared light waves. It does not involve atoms. Radiation is absorbed by dark dull objects and is reflected by shiny substances such as metals. You may have seen an athlete wrapped in a shiny blanket after a race this prevents the body temperature from dropping too quickly. Unit 2: You can learn more about radiation on page 45. Did you know? The warmth that we get from the Sun is from infrared radiation, coming from the Sun almost 92 million miles away. Assessment activity 2.3 P1 PLTS 1 Explain why the whole of a pan of soup gets hot, even if you don t stir it. P1 2 Work in groups of three. Produce a leaflet showing different ways that we use heat transfer in the home and the workplace. P1 Producing the leaflet in your groups will help you develop team-working and self-management skills Grading tip Remember that solids transfer thermal energy by conduction and liquids and gases by convection. Radiation is light and doesn t need a medium to transfer thermal energy. 43

10 BTEC s own resources 2.4 Catch that energy In this section: P1 M1 D1 The cost of energy is going up and our non-renewable energy resources are going down. Minimising loss of energy is becoming important for all of us. Also, in generating the energy that we use, carbon dioxide gas is given off, which is thought to be responsible for making the Earth warmer. This means that reducing energy loss is good not only for our pockets but also for our planet. Activity A Look at the thermal image of the house. Identify which areas of the house are losing energy. Heat is lost from our houses mostly through the walls and roof, and to a lesser extent through the doors, floor and windows. The diagram below shows how energy can be saved. The red areas in this thermal image of a house show where most heat energy is being lost. Loft insulation prevents heat loss through the roof by conduction and convection Grading tip P1 Remember that the criteria, M1 and D1 need to relate to each other. So when you are planning the investigation P1, make sure that it relates to minimising energy in the home or workplace. Make sure you include experiments on conduction, convection and radiation. Silver foil behind radiators prevents heat loss by radiation as does painting walls white Carpets on floors prevent heat loss by conduction Cavity walls filled with foam prevents heat loss through the walls by conduction and convection. Metal foil can reflect radiation. Methods of insulating a house. Double glazing in windows prevents heat loss by convection Draught proofing in doors and windows and curtains prevent heat loss by convection Assessment activity 2.4 Background photo P1 D1 D1 to come 1 Investigate your own house. List the methods that are used to minimise energy loss. P1 D1 2 What else might you do to minimise energy loss from your house? D1 44

11 WorkSpace Kevin Wright Principal Manufacturing Engineer, Astrium Ltd I am an engineer working in the UK s Space Industry and I m involved with production of electronic circuits which will be fitted in a satellite to work in Space. My responsibilities include: electronic circuits, including instructions on using equipment safely (Control of Substances Hazardous to Health). We have to tell people if a material is hazardous and what to do if they come into contact with it necessary for them to be used in space. The best thing about the job I like working with end-products which will actually go into Space. I enjoy my work because it can affect our everyday lives. Our satellites can help climatologists better understand our environment by observing climate change, or can help improve global communications and the quality of television broadcasts from space. Scenario Our work has to meet high standards set by external bodies such as the European Space Agency. When we make electronic circuits we use very thin gold wires to electrically connect microchips to the rest of the circuit. These wires are thinner than human hair but have to be strong enough to survive huge forces and vibrations during rocket launch once the circuit is inside a satellite. Each wire is tested by pulling it with a special machine to make sure that it won t break. Think about it! A new machine arrives from America but is only wired to connect to their 120 V mains supply. What would you do? You have installed a new component cleaning process but the chemical it needs doesn t have a COSHH certificate. What would you do? 45

12 BTEC s own resources 2.5 Efficiency In this section: Key terms P2 Input the energy that goes into a system. Output the energy that goes out of the system. Tungsten filament light bulb the standard type of light bulb in which the filament (the tightly curled wire that glows) is made out of the metal tungsten. M4 Often, a lot of the energy that goes into a system is wasted, mainly as heat. To save energy and money, electronics manufacturers are developing appliances that make better use of energy and therefore waste less. We describe these as energy efficient. One successful example is the energy-saving light bulb. The energy that is usefully used by an appliance is given by the efficiency, which we can calculate using this equation: efficiency = useful energy output from the system 100% total energy input to the system The efficiency is usually given as a percentage, so it varies from 0 to 100%. Maximum efficiency is indicated by 100%, meaning that all the energy input is converted to useful energy output. For example, petrol engines in cars transfer only 30% of the chemical energy in the fuel to kinetic energy used to move the car. Electric cars are more efficient. Activity A Write down the ways in which a petrol-engine car wastes energy. Worked example Energy-saving bulbs waste up to 75% less energy through heat than standard tungsten filament light bulbs. Activity B Work out the efficiency of a fluorescent lamp if the useful energy given out each second is 60 J. Assume that it has the same energy input as the tungsten filament lamp of 100 J. Which is more efficient? The energy input per second to a desk lamp with a standard tungsten filament light bulb is 100 J and the output light energy (useful energy) is 5 J. Energy expressed as joules per second is actually the power, which has the unit of watts and the symbol W. How efficient is the lamp? Give your answer as a percentage. Using the equation P3 above: P5 M3 D3 efficiency = % = 5% This lamp is only 5% efficient. Where do you think the other 95% of the energy goes? energy input useful energy output 46

13 Unit 2 Energy and our Universe Saving our world s energy resources There are many sources of energy. They can be divided into two types: renewable and non-renewable. Renewable energy sources are sources that will never run out. Non-renewable energy sources cannot be replaced once they have been used. Did you know? UK businesses waste 8.5 billion worth of energy every year. Type Source Energy Uses Nonrenewable Fossil fuels (remains of dead plants and animals that died millions of years ago) Thermal energy obtained by burning oil, natural gas and coal Powering vehicles, heating homes, generating electricity Nonrenewable Nuclear Thermal energy given off during the splitting of atoms Generating electricity Renewable Wind Kinetic energy transferred to wind turbines Renewable Biofuels Crops are fermented to make ethanol. This is burned to give thermal energy Renewable Sun Thermal energy captured by solar panels Generating electricity Powering cars Heating water in homes, generating electricity Energy assessors calculate an energy rating of your home you need this if you want to sell. Assessment activity 2.5 P2 M4 Functional skills 1 An electricity company has designed a power station using the potential energy in water from hill reservoirs. The average input is 800 MW and the average output is 200 MW. What is the efficiency? P2 You are a member of a committee set up by the government to investigate options for different energy sources. 2 Work in groups of four with each person choosing a different energy source. Then undertake research to find out the efficiency, cost, amount of energy that can be produced and the advantages/ disadvantages of each energy source. M4 3 Present your findings to the rest of the group, then discuss which energy sources are most suitable to meet the country s energy needs. M4 4 Produce a leaflet that outlines your recommendations with the reasons why. M4 You could use your ICT skills when making your leaflet. Grading tip P2 To meet you will need to calculate the efficiency of the energy transformations you investigate in P1. Remember that the useful energy output will always be less than the input energy. 47

14 BTEC s own resources 2.6 Understanding waves In this section: P3 Key terms Displacement how far the wave is disturbed from its rest position. Oscillation a complete to and fro movement; this could be going up and down, or sideways. We are surrounded by waves, but mostly invisible ones. What other waves can you think of? A beach is an obvious place to see waves in the sea. But this isn t the only place you ll find waves they are all around us. You are using waves to read this sentence. Light waves are reflected from the book into the retinas of your eyes, where the information is turned into electrical signals which are sent to your brain from your eyes. Sound waves carry music from a radio to your ears. Activity A List three examples of waves that you have used today. amplitude wavelength/period Diagram of wave showing amplitude, wavelength and period. equilibrium position What is a wave? The diagram on the left shows a wave. The properties of a wave are described using the terms amplitude, wavelength, frequency, period and speed. The amplitude of a wave is the maximum displacement from its fixed position. This is also called its equilibrium position. The wavelength of the wave is the distance between two identical points on the wave as it repeats itself. The period is the time for one complete oscillation. Frequency and speed The frequency of a wave is the number of complete oscillations it makes in one second. The unit of frequency is the hertz (Hz). Because many waves oscillate very quickly, frequency is often given in kilohertz (khz), which means 1000 waves in one second, or even megahertz (MHz), which means one million waves in one second. 48

15 Unit 2 Energy and our Universe The frequency and period of a wave are related by the equation: period = 1 frequency so the period decreases as the frequency increases. Worked example The frequency of microwaves used by a microwave oven is 2000 MHz. What is the period of the microwaves? First remember to change the frequency prefix to a standard number MHz is Hz. 1 period = frequency = 1 ( ) period = seconds (half of a billionth of a second) Did you know? Light travels at a speed of approximately 300 million metres per second. This value is true for all types of light. We write this as m/s. Sound waves are much slower in air they travel at about 330 m/s. The speed of a wave, which is how quickly it travels along, depends on both the frequency and wavelength. It is given by the equation: speed = wavelength frequency The speed will be in metres per second (m/s), wavelength in metres (m) and frequency in hertz (Hz). Case study: Keep your distance Alan works as an engineer for a car company. He is helping to design a safety system that uses light waves to work out how far away the car in front is. If you are too close to the car in front, the system slows your car down automatically. In an emergency it would automatically apply the brakes for you. Can you think of another situation in which this technology would be useful? Assessment activity 2.6 P3 1 In groups, discuss how you could model the movement of a wave. P3 2 Construct your model or role play it to the other groups. P3 Light can be used to sense the distance between a car and other objects. Grading tip Remember that the longer the wavelength the smaller the frequency. When calculating the speed, make sure that you change the prefixes (e.g. the M in MHz) to numbers, otherwise your answers will be wrong! 49

16 BTEC s own resources 2.7 Understanding the electromagnetic spectrum In this section: Key term P3 P5 M3 D3 Electromagnetic spectrum the different types of electromagnetic radiation, arranged in the order of frequency and wavelength, from radio waves to gamma rays. The electromagnetic spectrum Electromagnetic radiation is a wave. The colours of the rainbow are just the small range of radiation that our eyes can detect as visible light. Electromagnetic radiation outside this range is invisible to humans. All of the different wavelengths and frequencies of radiation, from radio waves, through visible light to X-rays and gamma rays, form the electromagnetic spectrum. low energy radio waves Used for receiving satellite signals and for cooking. microwaves Visible light: the shortest wavelength our eyes can see is violet (410nm) and the longest is red (710nm). Increasing Frequency infra red V ultra violet (uv) Increasing Wavelength X-rays Can be dangerous to the human body. Used to treat cancer. high energy gamma rays Used for TV and radio, and for picking up signals from deep space. Invisible to the human eye, used by TVs, DVD players, mobile phones etc. Given off by the Sun. Long exposure can cause skin cancer, but UV light can be useful too. Can be dangerous to the human body. Used to take images of bones. The electromagnetic spectrum and some of its applications. Activity A Put these types of electromagnetic radiation in order of increasing wavelength: visible green light, X-rays, microwaves, ultraviolet. Visible light is measured in nanometres. A nanometre is a billionth of a metre. All radiation that makes up the electromagnetic spectrum travels at a speed of about 300 million metres per second. Activity B Give one application each for microwaves, gamma rays and infrared light. The colours of a rainbow are just a small part of the electromagnetic spectrum. Understanding waves in communication Many electronic devices use electromagnetic waves in some way. Some require wires to work, some don t. The table on the next page shows some examples of wireless and wired communication. 50

17 Unit 2 Energy and our Universe Method of transmission Wires Examples Advantages Disadvantages Cable TV, Internet and phone calls; infrared is sent through optical fibres Excellent picture quality Can only be intercepted by physical access Difficult to use as and where you want Cables must be laid Did you know? The honey bee can see ultraviolet light. Snakes such as the viper can see infrared. (a) Wireless Wireless keyboards, mice and remote controls; all using infrared TV and games consoles can be controlled from a distance Keyboards/mice can be placed in a suitable place without having to rearrange wires Phones, keyboards, mice: heavy battery use Wireless phones, laptops; all using radio waves Laptops can be used in different parts of the house Laptops: signals can be intercepted remotely (b) Wireless Satellite; use of microwaves to transmit TV and mobile phone communication Can cover large distances Can carry a lot of TV stations; TV, radio and Internet can be accessed in remote areas There is a delay in communication Very expensive to set up (c) Assessment activity 2.7 P5 M3 D3 You have just started work as a salesperson at a telecommunication company. You are researching the market. 1 Find out which parts of the electromagnetic spectrum are used for communications. P5 2 Think of two types of communication devices that you have used today that rely on electromagnetic radiation to work. P5 3 Working in pairs, one of you should take the role of trying to sell with-wire technology, using a specific example from the table. The other should try to sell wireless technology, using a different example. After the role play summarise what you have found out by writing an advert. M3 D3 Communication: (a) cable using optical fibres, (b) satellite dish, (c) Wi-Fi wireless connection. Grading tip P3 In order to meet, make sure that you can describe all the areas of the spectrum that are covered on these pages. To meet P5 you need to describe both wireless and wired communication. 51

18 BTEC s own resources 2.8 Understanding radiation In this section: Key terms P4 M2 D2 Nucleus the inner part of the atom, where protons and neutrons are found. Radiation energy spreading out, as carried by electromagnetic radiation, or carried by a particle. Ionising radiation radiation that can remove electrons from atoms, causing the atom to become positively charged. Non-ionising radiation radiation that does not remove electrons from atoms, e.g. microwaves or infrared. A stable nucleus has the right number of protons and neutrons so it does not break apart. If the number of protons and neutrons changes, the nucleus becomes unstable and emits ionising radiation. This radiation has three types: alpha, beta and gamma. They differ in how ionising and how penetrating they are, and how they react to magnetic or electrical fields. Non-ionising radiation is radiation from the low frequency end of the electromagnetic spectrum: radio, microwave, infrared and visible light. Alpha ( ) radiation Alpha radiation consists of particles. These are helium nuclei, each having two protons and two neutrons, and a charge of +2. When particles hit another substance, e.g. air, they knock electrons off the particles they hit. This leaves the particles with a positive charge; the particles have been ionised. Alpha radiation is highly ionising. (If you swallow particles, they cause serious damage because they ionise DNA.) particles are large compared with electrons and protons so they cannot penetrate far into a material. For example, a few centimetres of air or a sheet of paper will stop particles. particles are weakly penetrating. This means there is little chance of particles getting into the human body through the skin. Because particles have a positive charge, they will be attracted to a negatively charged plate. Activity A Describe alpha radiation. When we think of radiation, we usually think of things like nuclear bombs and radiation leaks, which are uncontrolled radiation and are extremely dangerous. However, medical physicists can use controlled radiation to kill cancer cells in tumours. Beta ( ) radiation Beta radiation consists of fast-moving electrons that have been given off (emitted) by unstable nuclei. If they collide with an atom, they can knock off an electron and ionise the atom. Because particles are small, they don t ionise as much as particles. They are moderately ionising. Because they are less strongly ionising, particles can travel further than particles. They can travel through a few millimetres of aluminium before they are stopped. They are moderately penetrating. This makes them dangerous if they come into contact with living things. Because particles are electrons, which have a negative charge, they will be attracted to a positively charged metal plate. They are deflected more than particles because they are lighter. 52

19 Unit 2 Energy and our Universe Gamma ( ) radiation Gamma radiation is high-energy electromagnetic radiation. It has a very short wavelength and is emitted from unstable nuclei. Electromagnetic radiation does not have charge so it is difficult for radiation to ionise particles. But because it has very high energy it can still ionise matter. It is weakly ionising. Because radiation is weakly ionising it can travel large distances. It can pass through aluminium and even several centimetres of lead. It is highly penetrating. This means that radiation is extremely dangerous, both outside and inside the human body. Because it does not have a charge, it is not deflected by electric or magnetic fields. negative plate positive plate The effect of an electric field on, and radiation. Using ionising radiation aluminium Alpha radiation is used in smoke alarms. A weak alpha source ionises the air and causes a small current to flow. If smoke gets into the detector, the current reduces and the alarm sounds. Beta radiation is used to control the thickness of paper during production in a paper mill. A Geiger counter measures how much radiation passes through the paper. This is used to control the pressure on the rollers that the paper passes through. Gamma radiation is used to kill bacteria in food so that the food does not go bad. It is also used in the treatment of cancer. lead Penetration of, and radiation. Safety and hazards We are exposed to tiny doses of radiation in our everyday lives. This is called background radiation. Some of this radiation comes from the food we eat, in the form of radioactive potassium. Wherever there is a danger of being exposed to higher levels of radiation, especially in the workplace, you will see this symbol. Activity B Describe three useful applications of radiation. Assessment activity 2.8 P4 M2 D2 Grading tip You are working for a science charity to produce a poster or presentation on radiation. 1 Describe two properties each of, and radiation and give an application of each. P4 2 Describe the applications and dangers of radiation. One of you should investigate applications and the other should investigate the possible dangers in using these applications. Use a computer to prepare a poster or some presentation slides. M2 D2 For P4, make sure you can describe the nature of the different types of radiation and their absorption properties. For M2, don t forget to include applications of non-ionising radiation (pages 50 51). To get D2, make sure that you relate the ill effects to each type of ionising and non-ionising radiation. 53

20 BTEC s own resources 2.9 Understanding electricity In this section: P6 P8 Key terms Series in a series circuit the components are connected in a line, end to end, so that current flows through all of them one after the other. Parallel in a parallel circuit the components are in separate paths and the current is split between the paths. What is electricity? Imagine your world without electricity: no lights, no television, no central heating, no shower. It would be a strange place. Electricity is the flow of electrical charge. The charge could be positive and negative ions, as inside the battery of your mobile phone, or negatively charged electrons, as in the wire of your DVD player. When charge flows we say there is a current. Electrical energy allows a current to flow in a circuit. For example, when your DVD player is connected to the mains, it forms a circuit. A measure of the energy carried between two points in a circuit is called voltage or potential difference (pd). The two points could be each end of the bulb in the circuit shown. Series circuit. switch battery resistor bulb A ammeter V voltmeter An electric circuit diagram of a bulb, switch, fixed resistor, voltmeter and ammeter. We use a voltmeter to measure voltage and an ammeter to measure current. The way we connect the meters is important. A voltmeter is always connected in parallel. An ammeter is connected in series. The picture above shows a typical circuit diagram of a light bulb with the symbols of the different components. Parallel circuit. Case study: Fault finder Sophia is a technician at an electronics company. Today she is repairing a DVD player that seems to have no power. She wants to measure the voltage and find out if there is a break in the circuit. How could she do this? 54

21 Unit 2 Energy and our Universe Ohm s law Ohm s law describes how a current and voltage behave in metals. This law can be written as: voltage = current resistance V = I R Activity A What meter is used to measure current? How should the meter be connected in order to measure the current through the circuit? Draw a diagram to show this. In a practical you can use an ammeter and a voltmeter to check the values you calculate for a circuit using Ohm s law. High levels of current can be dangerous. In the laboratory we use only low levels such as a thousandth of an amp (ma) or a millionth of an amp (MA). All electrical devices, such as televisions, hairdryers and light bulbs, have resistors. These limit the current that flows through the components, as they could be damaged if too much current flows through them. Worked example Safety and hazards Electrical current is dangerous as it could cause the heart to stop working. You can also get burns from where the current enters and leaves the body. Before working with electrical equipment make sure you ask for a safety briefing from your supervisor. 1 What is the voltage across a 300W speaker if the current flowing is 0.01 A? voltage = current resistance = = 3 V 2 If the voltage across the speaker was 9V, what current would be flowing? voltage = current resistance so current = voltage resistance = = 0.03 A Table: Units and symbols of electrical properties Electrical property Unit Voltage volt V Current ampere or amp Symbol Resistance ohm (Greek symbol omega) A Functional skills Assessment activity 2.9 You are an electrician. Part of your work is to make sure that electrical circuits are working correctly. To do this you must understand Ohm s law and how to use measuring instruments. 1 Draw the symbols for a voltmeter and an ammeter. P6 2 This question uses Ohm s law. If a resistor in a circuit is 1500 Ω, what is the current through it if it is connected across a 1.5 V supply? P6 3 Using a circuit diagram, show how you could confirm the current and voltage readings in question 2 by using the correct measuring instruments. P8 P6 P8 Correctly obtaining the value of the current involves identifying the problem and selecting the correct mathematical method. Grading tip Make sure that when you perform electrical calculations you change the prefix (e.g. m in ma) to numbers. 55

22 BTEC s own resources 2.10 Producing electrical energy batteries In this section: P6 Activity A Write down three appliances you have used today that are powered by batteries. Were the batteries rechargeable or non-rechargeable? You have probably used something powered by a battery today your alarm clock or watch, mp3 player or a remote control. If you look at a battery you will see two terminals. One is a positive terminal, called the anode. The other is a negative terminal, called the cathode. In some batteries, such as AA, C and D batteries, the ends form the terminals. Table: Examples of different types of batteries and where we use them. Appliance Battery material Battery type Did you know? A battery produces electricity by the chemical reactions that take place inside it. The chemical inside a battery is called an electrolyte. Batteries can be rechargeable or non-rechargeable. Mobile phone Lithium ion Rechargeable Modern car Lithium acid Rechargeable Very old car Lead acid Rechargeable Laptop Lithium ion Rechargeable Television remote control Alkaline Non-rechargeable Watch Lithium-iodide Non-rechargeable (a) (b) Symbols for (a) a cell and (b) a battery. The electricity produced in batteries is described as direct current (dc). Direct current flows in one direction and does not change direction. Non-rechargeable batteries A battery is made up of a number of cells. For example, the popular AAA battery is a single cell (although we call it a battery) that supplies 1.5 V. The flat PP3 is a battery that consists of six 1.5 V cells connected in 56

23 Unit 2 Energy and our Universe series. It therefore supplies 9 V. Non-rechargeable batteries contain what are called dry cells. A dry cell is shown on the right. A chemical reaction takes place between the electrolyte and the anode which produces electrons at the anode. These electrons want to flow towards the cathode where there aren t many electrons, but the salt bridge is in the way. When a wire is placed across the electrodes, the electrons flow through it from the anode to the cathode generating current. The chemicals are gradually used up, until there are none left to produce charge. The battery then stops working. We use non-rechargeable batteries for items that need little current, such as remote controls, or for things that we don t use often, such as an emergency torch. These batteries are cheap and don t lose their energy (called self-discharge) as quickly as rechargeable batteries. However, they do contain chemicals that are harmful to the environment if they go into landfill. Unit 16: See page xxx for information about making batteries. Cross-section of a dry cell. metal or graphite cathode electrolyte paste paper or cardboard salt bridge metal (often zinc) anode Activity B What kind of electricity is produced by a battery? Why does it have this name? Safety and hazards Rechargeable batteries Cells in rechargeable batteries are called secondary cells. These batteries are mostly used in portable items that are used regularly, such as mobile phones and laptop computers. The chemical is used up as the battery is used, but in this case the process is reversible. The battery can be recharged by applying an electric current to it, which reverses the chemical reactions that take place during its use. Dead batteries must be disposed of safely. Some batteries contain toxic mercury that may leak into the environment. Leaking batteries may also cause burns if the acid inside comes into contact with skin. In some areas of the UK, all types of battery can be recycled. Assessment activity 2.10 P6 1 Explain the difference between a rechargeable and a nonrechargeable battery. Give five examples of uses of each. P6 2 Draw a labelled diagram of a primary cell. P6 3 Discuss with a partner the advantages and disadvantages of rechargeable and non-rechargeable batteries. P6 Grading tip To meet part of the grading criterion for P6, make sure that you include a diagram for the primary cell. To get all of the P6 criterion you need to also describe another way of generating electricity. A rechargeable car battery. 57

24 BTEC s own resources 2.11 Producing electrical energy non-renewable sources In this section: P6 M4 turbine generator transformer Key terms Non-renewable energy sources energy source that we cannot replace, for example, fossil fuels. Mains electricity electricity that comes into our homes and places of work. The voltage is normally 230 V and the frequency is 50 Hz. Safety and hazards Nuclear power stations generate nuclear waste, which is radioactive. It is very dangerous and needs to be stored safely for thousands of years until it is no longer radioactive. People living near nuclear reactors also worry about radioactive leaks that may occur in the running of the plants. Did you know? In the UK, almost 79% of the electricity generated comes from fossil fuels and about 5% is generated by nuclear energy. Nuclear power stations are about 30% efficient similar to those that use fossil fuels. boiler heat cooling tower Electricity generation and distribution. national grid Most power stations produce electricity by heating water to create steam. This steam is used to turn turbines which then rotate a generator to produce electricity. The electricity is then sent to our homes via the national grid. The water is often heated by non-renewable energy sources. Fossil fuels In many power stations the non-renewable sources of energy are in the form of fossil fuels: oil, coal or gas. The efficiency of most fossil fuel power stations is only about 30%, although the efficiency of newer ones may be as high as 50%. When fossil fuels burn, carbon dioxide (CO 2 ) is given off, which is a form of air pollution. Unit 2: See page 46 for how efficiency is calculated. Nuclear power In a nuclear power station, energy given out during nuclear reactions is used to heat water to create the steam. No burning of fuel takes place. Electricity generated by nuclear power plants does not create CO 2 and is relatively cheap to produce. It does produce radioactive waste. Producing electricity ac generators Electrical generators use induction to supply electricity. The turbine that is turned by the steam created in the power station boilers then rotates a generator which is a large coil of wire between magnets. The magnetic field induces a current in the coil. The diagrams on the next page show a simple ac (alternating current) generator and the output produced (compared with a direct current). 58

25 Unit 2 Energy and our Universe steady rate of rotation dc signal, sign is not changing direction with time N slip rings coil S brushes alternating voltage meter pointer swings from side to side Voltage (V) Time (s) A simple ac generator. The current generated by the coil is delivered to the circuit via springy metal contacts called brushes which rest on the slip rings. The brushes and slip rings allow constant contact with one side of the coil even though it is rotating. The alternating current is due to the sides of the coil moving through the magnetic field in opposite directions. Activity A Write down the name of the device that produces alternating current. The mains electricity supply in our homes is an alternating current with a frequency of 50Hz. This means the current changes direction 50 times every second. Case study: Let s get efficient Mary is a trainee engineer working for an electricity company. Part of her job involves investigating ways to make the electricity generators more efficient. Make a list of all the areas in a power station where energy may be wasted and the ways that these losses may be reduced. Assessment activity 2.11 M4 You must produce a report on nuclear power for an electricity company. 1 Draw a pie chart to show the percentages of electricity that are produced in the UK from fossil fuels and nuclear power. P6 2 Discuss with a partner the advantages and disadvantages of fossil fuel power and nuclear power. Which is more efficient and what are the effects on the environment? Put these arguments, along with your pie chart, into a report. M4 P6 ac signal, sign is changing direction with time Output from ac and dc generator. Science snippet The current produced by an ac generator can be increased by: using stronger magnets rotating the coil faster increasing the number of turns of wire on the coil making the coil thicker. Activity B List four ways that alternating current can be increased. Functional skills In discussing nuclear energy and fossil fuels as a way of producing electricity, you will develop both speaking and listening skills, as you present your arguments and listen to the views of others. Grading tip When you draw a pie chart, the total must add up to 100%. You will need to include electricity generated by alternative methods, which you can label as Other. 59