Energy and our Universe - Pearson Schools

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.

36 

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: 

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 

To achieve a merit grade the evidence 

must show that, in addition to the pass 

criteria, the learner is able to: 

Describe the energy transformations 

and the efficiency of the 

transformation process in 

these investigations 

See Assessment activity 2.2 

P1 M1 D1 

P2 

P3 

P4 

P5 

P6 

P7 

P8 

P9 

P10 

Calculate the efficiency of energy 

transformations 


Describe the electromagnetic 

spectrum 


Describe the different types of 

radiation, including non-ionising and 

ionising radiation 


Describe how waves can be used for 

communication 


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 


Describe the use of measuring 

instruments to check values predicted 

by Ohm’s law in given electric circuits 


Describe the composition of the 

solar system 


Identify evidence that shows how the 

universe is changing 


Describe the uses of ionising and 

non-ionising radiation in the home 

or workplace 


M2 D2 

M3 

M4 

M5 

M6 

Explain the advantages of wireless 

communication 


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 


Explain how the evidence shows that 

the universe is changing 


To achieve a distinction grade the 

evidence must show that, in addition to 

the pass and merit criteria, the learner 

is able to: 

D3 

D4 

D5 

D6 

Explain how energy losses due to 

energy transformations in the home 

or workplace can be minimised 

to reduce the impact on the 

environment 


Discuss the possible negative effects 

of ionising and non-ionising radiation 


Compare wired and wireless 

communication systems 


Assess how to minimise energy losses 

when transmitting electricity and when 

converting it into other forms for 

consumer applications 


Evaluate the main theory of how the 

universe was formed 


Evaluate the evidence that shows how 

the universe is changing 

See Assessment activity 2.14

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. 

Unit 2 Energy and our Universe 

Catalyst 

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2.1 Understanding types of energy 

In this section: 

Sound energy is used to test 

metals in the aerospace and 

automotive industries. Cracks, or 

weak areas, refl ect the energy. 

Grading tip 

P1 

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. 

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 

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 

Electrical Flow of charge in an 

electric circuit

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 

Assessment activity 2.1 

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 

. 


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. 

P1 

PLTS 

When you carry out your investigation 

you will be learning to enquire 

independently as well as developing 

your self-management skills. 

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2.2 Describing energy 


Key terms 

P1 

Energy block diagram – shows the 

forms of energy going into and out of 

a system. 

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. 

Engineers design aeroplanes 

to be as energy effi cient as 

possible. 

M1 

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 effi cient ‘energy-saving’ light bulbs in our homes. 

Case study: Energy-effi cient fl ight 

Jenny is a trainee engineer working for an aerospace company. She 

is working with other engineers to design a more effi cient 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? 

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. 

Wasted thermal 

(heat) and sound 

energy 

An energy block diagram showing the energy 

transfers that occur in a moving lorry. 

Kinetic energy 

used to move 

the lorry

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. 

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. 


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. M1 

3 350 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. 

P1 

Electrical energy used for radio, lights, 

recharging battery etc. 20 000 J 

Chemical energy 

from burning fuel 

200 000 J 

M1 

Wasted thermal (heat) 

and sound energy 100 000 J 

Kinetic energy used to move the lorry 

80 000 J 


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.) 

A Sankey diagram showing the size of the 

energy transfers for a moving lorry. 

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42 


2.3 Understanding thermal energy 


Key terms 

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 specifi c volume; something 

heavy that takes up a small space 

has a higher density than something 

that weighs the same but takes up 

more space. 

Vacuum fl asks keep liquids hot 

by minimising heat loss due to 

conduction, convection and 

radiation. 

P1 

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 fl ask 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. 

HEAT 

A non-metal transfers heat through the 

vibration of its atoms. These are poor 

conductors of heat but good insulators. 

HEAT 

free electrons 

A metal transfers heat through the 

movement of free electrons as well as 

through the vibration of its atoms.

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 

Radiation 

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. 

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. 

Assessment activity 2.3 P1 

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 

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. 

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. 

Did you know? 

The warmth that we get from the Sun 

is from infrared radiation, coming from 

the Sun almost 92 million miles away. 

PLTS 

Producing the leaflet in your groups 

will help you develop team-working 

and self-management skills 

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2.4 Catch that energy 


The red areas in this thermal 

image of a house show where 

most heat energy is being lost. 

Grading tip 

P1 

M1 

P1 

D1 

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. 

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. 

Loft insulation 

prevents heat 

loss through the 

roof by conduction 

and convection 

Silver foil behind 

radiators prevents 

heat loss by 

radiation as does 

painting walls white 

Carpets on 

floors prevent 

heat loss by 

conduction 

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, fl oor and windows. The diagram below 

shows how energy can be saved. 

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 

Background photo 

to come 

P1 D1 

D1 

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

WorkSpace 

Principal Manufacturing Engineer, Astrium Ltd 

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 

Kevin Wright 

I am an engineer working in the 

UK’s Space Industry and I’m involved with production 

of electronic circuits which will be fi tted 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. 

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 certifi cate. 

What would you do? 

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2.5 Effi ciency 


Key terms 

Input – the energy that goes into a 

system. 

Output – the energy that goes out of 

the system. 

Tungsten fi lament light bulb – the 

standard type of light bulb in which 

the fi lament (the tightly curled 

wire that glows) is made out of the 

metal tungsten. 

Energy-saving bulbs waste up to 

75% less energy through heat 

than standard tungsten fi lament 

light bulbs. 

Activity B 

P2 

M4 

Work out the effi ciency of a 

fl uorescent lamp if the useful energy 

given out each second is 60 J. Assume 

that it has the same energy input as 

the tungsten fi lament lamp of 100 J. 

Which is more effi cient? 

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 effi cient. One successful 

example is the energy-saving light bulb. 

The energy that is usefully used by an appliance is given by the 

effi ciency, which we can calculate using this equation: 

effi ciency = useful energy output from the system × 100% 

total energy input to the system 

The effi ciency is usually given as a percentage, so it varies from 0 to 

100%. Maximum effi ciency 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 effi cient. 

Activity A 

Write down the ways in which a petrol-engine car wastes 

energy. 

Worked example 

The energy input per second to a desk lamp with a 

standard tungsten fi lament 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 effi cient is the lamp? Give your answer as a 

percentage. 

Using the equation P3 above: P5 M3 D3 

effi ciency = 5 × 100% = 5% 

100 

This lamp is only 5% effi cient. 

Where do you think the other 

95% of the energy goes? 

energy input 

useful energy 

output

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. 

Type Source Energy Uses 

Nonrenewable 

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 

Nuclear Thermal energy 

given off during 

the splitting of 

atoms 

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 


Powering vehicles, 

heating homes, 

generating 

electricity 

Generating 

electricity 

Generating 

electricity 

Powering cars 

Heating water in 

homes, generating 

electricity 

P2 

M4 

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 


Did you know? 

UK businesses waste £8.5 billion 

worth of energy every year. 

Energy assessors calculate 

an energy rating of your 

home – you need this if 

you want to sell. 

Functional skills 

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. 

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amplitude 


2.6 Understanding waves 


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. 

wavelength/period 

Diagram of wave showing amplitude, 

wavelength and period. 

P3 

equilibrium 

position 

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. 

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 

We are surrounded by waves, but 

mostly invisible ones. What other 

waves can you think of? 

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.

The frequency and period of a wave are related by the equation: 


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. 2000 MHz is 2 000 000 000 Hz. 

1 

period = 

frequency = 

1 

(2 000 000 000) 

period = 0.5 × 10−9 seconds (half of a billionth of a second) 

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). 

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 

Grading tip 

period = 1 

frequency 

so the period decreases as the frequency increases. 

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? 


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! 

P3 


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 3 × 10 8 m/s. 

Sound waves are much slower – in air 

they travel at about 330 m/s. 

Light can be used to sense 

the distance between a 

car and other objects. 

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50 


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 colours of a rainbow 

are just a small part of the 

electromagnetic spectrum. 

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 TV and 

radio, and for picking 

up signals from 

deep space. 

Used for 

receiving satellite 

signals and for 

cooking. 

Visible light: 

the shortest wavelength 

our eyes can see is violet 

(410nm) and the longest 

is red (710nm). 

infra 

ultra 

microwaves V 

X-rays 

red 

violet (uv) 

Invisible to the 

human eye, used by 

TVs, DVD players, 

mobile phones etc. 

Increasing Frequency 

Increasing Wavelength 

Given off by the Sun. 

Long exposure can 

cause skin cancer, 

but UV light can 

be useful too. 

The electromagnetic spectrum and some of its applications. 

Activity A 

Can be dangerous 

to the human body. 

Used to treat cancer. 

high energy 

gamma 

rays 

Can be dangerous 

to the human body. 

Used to take images 

of bones. 

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. 

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.

Method of 

transmission 

Examples Advantages Disadvantages 

Wires Cable TV, Internet 

and phone calls; 

infrared is sent 

through optical 

fibres 

Wireless Wireless 

keyboards, mice 

and remote 

controls; all using 

infrared 

Wireless phones, 

laptops; all using 

radio waves 

Wireless Satellite; use of 

microwaves to 

transmit TV and 

mobile phone 

communication 

Excellent picture 

quality 

Can only be 

intercepted by 

physical access 

TV and games 

consoles can be 

controlled from a 

distance 

Keyboards/mice 

can be placed in 

a suitable place 

without having to 

rearrange wires 

Laptops can be 

used in different 

parts of the house 

Can cover large 

distances 

Can carry a lot of 

TV stations; 

TV, radio and 

Internet can be 

accessed in remote 

areas 


Difficult to use as 

and where you 

want 

Cables must be 

laid 

Phones, keyboards, 

mice: heavy battery 

use 

Laptops: signals 

can be intercepted 

remotely 

There is a delay in 

communication 

Very expensive to 

set up 

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 

P5 

M3 

D3 

(b) 


Did you know? 

The honey bee can see ultraviolet 

light. Snakes such as the viper can 

see infrared. 

(c) 

(a) 

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

52 


2.8 Understanding radiation 


Key terms 

P4 

M2 

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. 

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. 

D2 

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 fi elds. 

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. 

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 

defl ected more than particles because they are lighter.

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. 

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 


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 

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

54 

Series circuit. 


2.9 Understanding electricity 


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. 

Parallel circuit. 

P6 

P8 

What is electricity? 

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. 

switch 

resistor 

bulb 

V 

battery 

ammeter 

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. 

Case study: Fault finder 

Imagine your world without electricity: no 

lights, no television, no central heating, no 

shower. It would be a strange place. 

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? 

A

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 

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. 


1 What is the voltage across a 300W speaker if the current 

flowing is 0.01 A? 


= 0.01 × 300 = 3 V 

2 If the voltage across the speaker was 9V, what current would 

be flowing? 


so current = voltage 

resistance 

= 9 

= 0.03A 300 


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 



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. 

Table: Units and symbols of electrical 

properties 

Electrical 

property 

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. 

Unit Symbol 

Voltage volt V 

Current ampere or 

amp 

Resistance ohm (Greek 

symbol 

omega) 

Grading tip 

Make sure that when you perform 

electrical calculations you change the 

prefix (e.g. ‘m’ in mA) to numbers. 

A 


Correctly obtaining the value of 

the current involves identifying the 

problem and selecting the correct 

mathematical method. 

55

56 

(a) 

(b) 


2.10 Producing electrical 

energy – batteries 


Activity A 

Write down three appliances you 

have used today that are powered 

by batteries. Were the batteries 

rechargeable or non-rechargeable? 

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. 

Symbols for (a) a cell and (b) a battery. 

P6 

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 

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 

The electricity produced in batteries is described as direct current (dc). 

Direct current fl ows 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 fl at PP3 is a battery that consists of six 1.5 V cells connected in

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. 

Activity B 

What kind of electricity is produced by a battery? Why does it 

have this name? 

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. 

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. 

Cross-section of a dry cell. 


metal or 

graphite 

cathode 

electrolyte 

paste 

paper or 

cardboard 

salt bridge 

metal (often 

zinc) anode 


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. 

A rechargeable car battery. 

57

58 


2.11 Producing electrical energy – 

non-renewable sources 


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. 

Did you know? 

P6 M4 


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. 

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 

turbine 

Electricity generation and distribution. 

generator 

cooling tower national grid 

transformer 

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).

N 

slip rings 

A simple ac generator. 

steady rate of rotation 

coil 

S 

brushes 

alternating 

voltage 

meter pointer swings 

from side to side 

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. 


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 

M4 

Voltage (V) 


dc signal, sign is not 

changing direction with time 

Time (s) 

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. 


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

60 


2.12 Producing electrical energy – 

renewable sources 

In this 

section: 

Key term 

P6 

P7 

Transformer – a device that changes the 

voltage of an alternating current without 

changing its frequency. 

Did you know? 

M4 

Hydroelectric power stations 

are expensive to build but cost 

little to run and do not cause 

any pollution. 

D4 

Most of Norway’s electricity is 

produced by hydroelectric power, 

possible because of all its lakes and 

mountains. In the UK, only about 5% 

of electricity is produced in this way. 

The previous pages describe non-renewable energy sources. We can 

also generate electricity using natural energy such as solar power 

from the sun, wind or water power. These sources are described as 

renewable because they do not run out. 

Hydroelectric power 

Hydroelectric power stations are one example of the use of renewable 

energy sources. Water is stored behind a dam, often high up in the 

mountains. The height of the reservoir provides a source of potential 

energy. When the water is released and fl ows downhill, the potential 

energy is converted to kinetic energy and the energy transfer turns 

the turbines to generate electricity. Because no heating is required, 

there is no pollution. Hydroelectric power is thought to be the most 

effi cient method of generating electricity, with nearly 90% effi ciency. 

Unit 2: Energy transformations are described on pages 38–39. 

Activity A 

List the energy transformations that take place in a hydroelectric 

power station. 

Building a hydroelectric power station is expensive and some people 

are also concerned that they cause fl ooding and spoil the natural beauty 

of the area. 

Wind power 

Wind turbines use the kinetic energy of the wind to turn the turbines to 

produce electricity. No pollution is produced, but people worry that the 

wind turbines spoil the view of the countryside and about the noise the 

turbines produce. Although wind is free, wind turbines are expensive to 

set up and electricity generation depends on the wind – if there is no 

wind, no electricity is generated. When they do operate, the effi ciency is 

reported to be 35–60%. 

Solar power 

Solar power can be harnessed using solar cells called photovoltaic 

cells. When the sun shines on these cells they emit electrons which 

form a current. The solar panels are expensive, but the energy source 

is free and no pollution is produced. However, the amount of electricity 

generated depends on how bright the sunshine is. As with wind power, 

the effi ciency of energy conversion varies. It is reported as 12–25%.

Activity B 

Compare the efficiencies of three renewable methods used to 

generate electricity and list their advantages and disadvantages. 

Getting electricity to our homes 

and factories 

The UK has a network grid of pylon towers linked by copper cables that 

transfer electrical energy to our homes. The voltage produced at the 

power station is about 25 000V. Engineers then increase this voltage to 

400000V using a step-up transformer. Transferring electricity through 

the national grid at a higher voltage reduces energy losses during the 

transfer. The higher the voltage, the lower the current becomes so 

the lower the energy loss. Using thick cables also reduces energy loss 

because it decreases resistance. 

Unit 2: Ohm’s law, which describes the relationship between 

current and voltage, is described on page 55. 

We use 230V mains in our homes and up to 11 000 V in some factories. 

The voltage from the national grid is reduced using a step-down 

transformer. 

Assessment activity 2.12 P7 M4 D4 

1 Describe why the voltage used in the home is different from that 

used to transmit electricity over the national grid. P7 D4 

2 Which equipment is used to increase and decrease the voltage as 

electricity is transferred from the power station to our homes and 

factories? P7 D4 

3 Which type of renewable energy power station would you 

recommend to be built near your community? Prepare a 

presentation that describes the advantages and disadvantages 

including the impact on the local environment. M4 D4 

Grading tip 

For P7 

, ensure that you include each stage of electrical 

generation. Using a diagram will make your description clear. 

For M4 consider the efficiencies for both non-renewable 

energy, such as fossil fuels or nuclear generation, and 

renewable energy, such as hydroelectric and solar power. For D4 

remember to include “consumer products” in the discussion. 

These are products such as TVs, washing machines etc. 

step-up 

transformer 


40 000V 

25 000V 

step-down 

transformer 

consumer 

power station 

230V 

The national grid at work, showing 

transmission lines and transformers. 

61

62 


2.13 Understanding our universe 


Key term 

Orbit – the path of an object moving 

through space, such as the path of the 

Earth as it goes round the Sun. 

Did you know? 

Stars are so far away that their 

distances from us are measured in 

‘light years’. As the name suggests, a 

light year is the distance travelled by 

light in 1 year. Light travels 300 million 

metres in 1 second so a light year is 

about 10 13 kilometres. 

Case study 

P9 

Probing Near-Earth Objects 

(NEOs) 

Rachael is a technician at the 

European Space Agency. She is part 

of a group of scientists and engineers 

who are designing the next generation 

of space probes. Some of these 

probes will be used to collect samples 

from space objects close to the Earth, 

for example asteroids and comets. 

What could we learn from analysing 

these samples? 

The Solar System 

Stars being born. Each 

small bulge will eventually 

form into a collection of 

planets the size of our 

Solar System. 

The Solar System consists of the Sun and all objects that are attracted 

to the Sun by gravity. These include the eight planets and other objects 

such as asteroids and meteoroids. The Sun is the brightest star and is 

the centre of the Solar System. It contains almost 99.9% of all the mass 

in the Solar System. Because the Sun is so huge, its gravity holds the 

planets in their orbits around it. 

Objects in the night sky 

If you look at a clear night sky, you will see that it is fi lled with various 

objects. With the naked eye you can see the light of thousands of stars, 

which seem to be arranged in patterns, called constellations. Because 

the Earth rotates, the stars rise and set like the Sun. You will also see 

planets. These don’t shine their own light but refl ect light from other 

sources, such as the Sun. Because they are close to the Earth, they shine 

brightly and do not twinkle like stars. 

If you are lucky you may see an object with a bright tail. This is likely to 

be a comet. Comets are made from rock, dried ice and frozen gases 

such as carbon dioxide and methane. They come from outside our Solar 

System. You may also see ‘shooting stars’, which are meteors. These 

are bits of dust and rock that enter the Earth’s atmosphere. Astronomers 

have also discovered hundreds of stony objects called asteroids, which 

are also in orbit around the Sun.

Activity A 

Which objects in the night sky don’t shine with their own light? 

The Earth’s moon is clearly visible and its appearance changes through 

the month as it orbits the Earth. With a good telescope you can see that 

other planets also have moons. Jupiter has 63 moons. One of these, 

called Io, has active volcanoes on its surface. 

Origin of the Solar System 

Astronomers believe that the Solar System was formed when clouds 

of gas and dust collided, because of some sort of explosion that 

happened in space. Eventually our Sun was formed, together with other 

objects such as planets. Asteroids and meteoroids are believed to be 

the remains of that cloud. 

Geologists have investigated meteorites (meteors that have landed 

on Earth) and estimate they are 4.5 billion years old. The effect of 

meteoroids and asteroids that hit the surface of the moon is clearly seen 

as craters, even with the naked eye. Some astrophysicists believe that 

the Earth was formed by collisions of asteroids and meteoroids. 


You are an astronomer working for an observatory. You are invited to 

a primary school to describe our Solar System to young children. 

1 Working in groups of three, construct a model of the Solar System 

showing the distances of the eight planets from the Sun. 

2 In your groups, investigate the theory described above of how the 

Solar System was formed. Present your results in the form of a 

poster. P9 

Grading tip 

P9 

For : When describing the Solar System, make sure you 

include objects other than planets; there are many other 

objects out there apart from planets. 

PLTS 

Producing a model of the solar system will develop your creative 

skills and presenting your work will help you develop team skills. 

P9 

Asteroids 


Sun 

Mercury 

Venus 

Earth 

Mars 

Pluto 

Comet 

Jupiter 

Saturn 

Uranus 

Neptune 

The solar system is made up of the Sun, 

eight planets, the dwarf planet Pluto, 

asteroids and comets. Previously Pluto was 

thought to be a planet. 

63

64 

2.14 Understanding our universe – 

how did it all happen? 

In this 

section: 


Key terms 

P10 M5 M6 D5 D6 

Red shift – light from stars that 

are travelling away from us comes 

from closer to the red end of the 

electromagnetic spectrum than light 

from the Sun. 

Big Bang theory – the theory that the 

Universe began with an explosion. 

Cosmic background radiation – 

electromagnetic energy that comes from 

all directions in space and is predicted 

to have come from the Big Bang. 

Our Milky Way galaxy: its shape 

is a spiral and the Sun is near 

the edge, as shown in this 

representation. 

Our Universe 

The Universe is made up of many 

different objects. 

So far we have looked at our Solar System, but our Sun is not the only 

star in the region. It is one of about 100 billion stars in our galaxy, which 

is called the Milky Way. The Milky Way is a spinning spiral disc. On a 

clear dark night without any pollution or street lights, you can see it as a 

‘milkyish’ light band. 

Our Solar System is on the edge of the Milky Way. It takes about 220 

million years for our Solar System to orbit the Milky Way, even though it 

is estimated to be travelling at 100 000 miles per hour. This means that it 

has just completed one orbit since the fi rst creatures appeared on Earth. 

Our galaxy is the second largest in a group of seventeen galaxies. The 

nearest galaxy to the Milky Way is called M31, the Andromeda galaxy. 

Beyond this are other clusters of galaxies, with their own stars and 

planets. These clusters form a shape which is a little like a honeycomb. 

All these clusters make up what we call the Universe. Astronomers 

believe that there are about 100 billion galaxies in the Universe. 

Activity A 

What is the name of our galaxy? Name one other galaxy.

Expansion of the Universe 

Many astrophysicists believe that the Universe is expanding. You can 

imagine this as bread with raisins in it rising: the raisins represent the 

galaxies, moving away from each other as the bread rises. Light coming 

from galaxies has provided evidence for this expansion. 

Light forms a spectrum of wavelength and frequency. The visible part 

of the spectrum starts with violet and ends with red. The further you go 

towards red, the longer the wavelength. 

Astrophysicists have found that light coming from distant galaxies is 

shifted towards the red end of the spectrum. The more distant the 

galaxy, the bigger the shift is. They call this a red shift. (It is also known 

as the Doppler effect.) A possible explanation for this red shift is that 

the galaxies are moving away from us. This suggests that the Universe 

is expanding. 

Unit 2: The electromagnetic spectrum is described on pages 50–51. 

The Big Bang theory 

According to the Big Bang theory, galaxies and indeed the Universe 

were once a fixed point that then exploded. The theory also suggests 

that radiation was given off during this explosion, and that this 

radiation should still be detected today. This radiation is called 

cosmic background radiation and it was detected in the 1960s. NASA 

confirmed this discovery in 1992, using its newly built satellite called 

Cosmic Background Explorer (COBE). 

So what next for the Universe? Cosmologists believe that the Universe 

could follow one of the following paths. 

 

 

It could continue to expand for ever. 

The expansion will slow down, but won’t quite stop. 

The expansion could come to a complete stop, forming a massive 

black hole (singularity). 

Unit 18: See page xxx for more information about black holes. 


P10 M5 M6 D5 

You are being interviewed for a job at a space technology company. 

You must produce a presentation on space. In your presentation: 

1 List the evidence that suggests that the Universe is changing. P10 

2 Describe the evidence that indicates that the Universe 

is changing. M6 

3 Describe the strengths and weaknesses of this evidence. D6 

4 Describe the Big Bang theory of how the Universe was 

formed M5 ; how sure are you that this theory is correct? D5 

D6 


Did you know? 

In the centre of our galaxy (the Milky 

Way) there is a black hole that is 4 

million times bigger than our Sun. 

Activity B 

What does the Doppler effect tell us 

about our Universe? 

Grading tip 

To obtain P10 , make sure you include 

the red shift and the COBE as evidence 

that the universe is expanding. In 

attempting M6, 

remember that you 

need to describe how the evidence 

you identified for P10 suggests a 

changing universe. For D6 you 

need to discuss the evidence for and 

against stating that the universe 

is changing. 

65

66 


Just checking 

1. What is the difference between rechargeable and non-rechargeable batteries? 

2. With the aid of a diagram, describe how an ac electrical generator works. Sketch a graph showing 

the electrical current that is produced. 

3. Sketch the current provided by dc supply. 

4. Describe how electricity is brought to our homes. 

5. List three ways that heat is lost from a house. 

7. What is the name of our galaxy? 

8. How many planets are there in our Solar System? Name these planets. 

9. Name three types of radiation and give an application of each. 

To get the grade you deserve in your assignments remember the following. 

Assignment tips 

Make sure that your assignments are written as clearly as possible. Always read them through when you 

have fi nished. 

Make sure that, when you plan experiments, you have thought about what kind of results you expect to 

get and have prepared a table for them. What kind of apparatus is likely to be available? Make sure you 

plan well, allowing yourself plenty of time. 

Don’t forget to include the correct units when solving numerical problems. Always check your calculations 

before you hand in your work for assessment. 

Some of the key information you’ll need to remember includes the following. 

Knowing the difference between energy block diagrams and Sankey diagrams – remember the width of 

each arrow in a Sankey diagram corresponds to the value of the energy transferred. 

Knowing the difference between ionising and non-ionising radiation – remember ionising radiation 

knocks electrons out of the atoms it comes into contact with. 

When doing work on the electromagnetic spectrum, remember the smaller a wavelength is, the higher 

the frequency. 

Renewable sources of energy are those that don’t run out, for example wind energy and solar energy. 

Non-renewable sources of energy are ones that will run out, for example fossil fuels and nuclear fuels. 

You may fi nd the following websites useful as you work through this unit. 

For information on… Visit… 

the different types of energy, its transfer and uses http://www.gcse.com/energy.htm 

the full range of electricity generation technology http://www.electricitygeneration.co.uk 

energy-saving measures http://www.energysavingtrust.org.uk

Energy and our Universe - Pearson Schools

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