Unit 2 from the BTEC Level 2 First Applied Science Student Book
Transcript of Unit 2 from the BTEC Level 2 First Applied Science Student Book
Credit value: 5
Learning outcomesAfter 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.
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.
2 Energy and our Universe
BTEC’s own resources
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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
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
Calculate the efficiency of energy
transformations
See Assessment activity 2.5
Describe the electromagnetic
spectrum
See Assessment activity 2.6
Describe the uses of ionising and
non-ionising radiation in the home
or workplace
See Assessment activity 2.8
Discuss the possible negative effects
of ionising and non-ionising radiation
See Assessment activity 2.8
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
Explain the advantages of wireless
communication
See Assessment activity 2.7
Compare wired and wireless
communication systems
See Assessment activity 2.7
Describe how electricity can
be produced
See Assessment activities 2.9, 2.10
and 2.11
Compare the efficiency of electricity
generated from different sources
See Assessment activities 2.11
and 2.12
Assess how to minimise energy losses
when transmitting electricity and when
converting it into other forms for
consumer applications
See Assessment activity 2.12
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
Describe the main theory of how the
universe was formed
See Assessment activity 2.14
Evaluate the main theory of how the
universe was formed
See Assessment activity 2.14
Identify evidence that shows how the
universe is changing
See Assessment activity 2.14
Explain how the evidence shows that
the universe is changing
See Assessment activity 2.14
Evaluate the evidence that shows how
the universe is changing
See Assessment activity 2.14
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How you will be assessedYour assessment could be in the form of:
presentations
case studies
practical tasks
written assignments.
Unit 2 Energy and our Universe
37
Tariq, 18 years oldI 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
2.1 Understanding types of energyTypes of energyEnergy 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
BTEC’s own resources
Grading tip
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.
In this section:
Sound energy is used to test metals in the aerospace and automotive industries. Cracks, or weak areas, refl ect the energy.
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Unit 2 Energy and our Universe
Energy transformationsWe 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.
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.
2 What form of energy is in this drink?
3 Investigate what happens to this drink as it goes into your body.
Grading tipRemember, everything requires energy – even sleep! This means that you should be able to find enough types of energy to cover the content for .
Assessment activity 2.1
Using energy at home and in the workplaceWe use many different appliances at home and at work that convert
energy from one form into others.
Activity A
Write down three ways in which you have experienced energy being transformed today.
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.
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
Electrical energy used
for radio, lights,
recharging battery etc.
Kinetic energy
used to move
the lorry
Chemical energy
from burning
fuel
Wasted thermal
(heat) and sound
energy
An energy block diagram showing the energy transfers that occur in a moving lorry.
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BTEC’s own resources
In this section: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 energyYou 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 transformationsWe use energy block diagrams
to understand how energy
is transformed. This block
diagram shows the energy
transfers that occur
in a moving lorry.
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.
Key terms
Engineers design aeroplanes to be as energy effi cient as possible.
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Chemical energy
from burning fuel
200 000 J
Wasted thermal (heat)
and sound energy 100 000 J
Kinetic energy used to move the lorry
80 000 J
Electrical energy used for radio, lights,
recharging battery etc. 20 000 J
A Sankey diagram showing the size of the energy transfers for a moving lorry.
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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.
Useful versus wasteful energyIt 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.
2 Draw a block diagram to show the energy transformations.
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.
Assessment activity 2.2
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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.)
Grading tipRemember that when you draw a Sankey diagram, the amount of energy leaving the system must be the same as the energy that enters it.
2.3 Understanding thermal energyIn this section:
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.
Key terms
Vacuum fl asks keep liquids hot by minimising heat loss due to conduction, convection and radiation.
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.
ConductionYou 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
free electrons
A non-metal transfers heat through the vibration of its atoms. These are poor conductors of heat but good insulators.
A metal transfers heat through the movement of free electrons as well as through the vibration of its atoms.
HEAT
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BTEC’s own resources
P1
The warm air is less
dense so risesAs the air
cools down
it becomes
more dense
and sinks
The radiator heats
the air surrounding it
Cool air moves in
to replace the warm air
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.
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.
ConvectionThe 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.
This room is being heated by a radiator; the convection current is shown by arrows.
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Unit 2 Energy and our Universe
RadiationRadiation 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.
1 Explain why the whole of a pan of soup gets hot, even if you don’t stir it.
2 Work in groups of three. Produce a leaflet showing different ways that we use heat transfer in the home and the workplace.
Grading tipRemember 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.
PLTS
Producing the leaflet in your groups will help you develop team-working and self-management skills
Assessment activity 2.3 P1
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Grading tip
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
Cavity walls filled with foam
prevents heat loss through
the walls by conduction and
convection. Metal foil can
reflect radiation.
Draught proofing in doors and
windows and curtains prevent
heat loss by convection
Double glazing
in windows
prevents
heat loss by
convection
Methods of insulating a house.
Background photo
to come
D1
1 Investigate your own house. List the methods that are used to minimise energy loss.
2 What else might you do to minimise energy loss from your house?
Assessment activity 2.4
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BTEC’s own resources
2.4 Catch that energy
The red areas in this thermal image of a house show where most heat energy is being lost.
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.
In this section:
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.
Remember that the criteria ,
and need to relate to each
other. So when you are planning the
investigation , make sure that it
relates to minimising energy in the
home or workplace. Make sure you
include experiments on conduction,
convection and radiation.
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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.
ScenarioOur 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.
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.
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?
WorkSpace
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energy input
useful energy
output
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BTEC’s own resources
2.5 Effi ciencyIn this section:
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.
Key terms
Energy-saving bulbs waste up to 75% less energy through heat than standard tungsten fi lament light bulbs.
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 exampleThe 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 above:
effi ciency = 5
× 100% = 5%100
This lamp is only 5% effi cient. Where do you think the other 95% of the energy goes?
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Activity B
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?
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Unit 2 Energy and our Universe
Did you know?
UK businesses waste £8.5 billion worth of energy every year.
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
Non-
renewable
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
Non-
renewable
Nuclear Thermal energy
given off during
the splitting of
atoms
Generating
electricity
Renewable Wind Kinetic energy
transferred to wind
turbines
Generating
electricity
Renewable Biofuels Crops are
fermented to
make ethanol. This
is burned to give
thermal energy
Powering cars
Renewable Sun Thermal energy
captured by solar
panels
Heating water in
homes, generating
electricity
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?
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.
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.
4 Produce a leaflet that outlines your recommendations with the reasons why.
Assessment activity 2.5 Functional skills
You could use your ICT skills when making your leaflet.
Grading tip
To meet you will need to
calculate the efficiency of the energy
transformations you investigate in
. Remember that the useful
energy output will always be less than
the input energy.
Energy assessors calculate an energy rating of your home – you need this if you want to sell.
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amplitude
equilibrium
position
wavelength/period
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BTEC’s own resources
2.6 Understanding wavesIn this section:
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.
Key terms
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 speedThe 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.
We are surrounded by waves, but mostly invisible ones. What other waves can you think of?
Diagram of wave showing amplitude, wavelength and period.
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Unit 2 Energy and our Universe
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. 2000 MHz is 2000000000 Hz.
period = 1
frequency =
1(2000000000)
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).
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 × 108 m/s. Sound waves are much slower – in air they travel at about 330 m/s.
1 In groups, discuss how you could model the movement of a wave.
2 Construct your model or role play it to the other groups.
Grading tipRemember 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!
Assessment activity 2.6
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?
The frequency and period of a wave are related by the equation:
period = 1
frequency
so the period decreases as the frequency increases.
Light can be used to sense the distance between a car and other objects.
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Vinfra
red
ultra
violet (uv)
gamma
rays
radio
wavesmicrowaves X-rays
low energy
Used for
receiving satellite
signals and for
cooking.
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.
Can be dangerous
to the human body.
Used to treat cancer.
Visible light:
the shortest wavelength
our eyes can see is violet
(410nm) and the longest
is red (710nm).
high energyhigh energyIncreasing Frequency
Increasing Wavelength
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BTEC’s own resources
2.7 Understanding theelectromagnetic spectrum
Electromagnetic spectrum – the
different types of electromagnetic
radiation, arranged in the order of
frequency and wavelength, from radio
waves to gamma rays.
Key term
The electromagnetic spectrumElectromagnetic 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.
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.
Activity B
Give one application each for microwaves, gamma rays and infrared light.
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.
Understanding waves in communicationMany 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.
The colours of a rainbow are just a small part of the electromagnetic spectrum.
In this section:
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Unit 2 Energy and our Universe
Did you know?
The honey bee can see ultraviolet light. Snakes such as the viper can see infrared.
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.
2 Think of two types of communication devices that you have used today that rely on electromagnetic radiation to work.
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.
Assessment activity 2.7
Method of
transmission
Examples Advantages Disadvantages
Wires 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
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
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
Grading tip
In order to meet , make sure
that you can describe all the areas
of the spectrum that are covered on
these pages. To meet you need
to describe both wireless and wired
communication.
Communication:(a) cable using optical fibres, (b) satellite dish, (c) Wi-Fi wireless connection.
(a)
(b)
(c)
P5
M3 D3
D3M3P5
P3
P5
P5
52
BTEC’s own resources
2.8 Understanding radiationIn this section:
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.
Key terms
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 ( ) radiationAlpha 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 weaklypenetrating. 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 moderatelypenetrating. 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.
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.
D2M2P4
positive plate
negative plate
leadaluminium
53
Unit 2 Energy and our Universe
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.
Gamma ( ) radiationGamma 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.
Using ionising radiation 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.
The effect of an electric field on , and radiation.
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.
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.
Assessment activity 2.8 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.
D2
P4
M2 D2
M2P4
Activity B
Describe three useful applications of radiation.
batteryswitch
resistor
bulb
voltmeter
ammeterA
V
Series circuit.
54
BTEC’s own resources
2.9 Understanding electricityIn this section:
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.
Key terms
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.
An electric circuit diagram of a bulb, switch, fixed resistor, voltmeter and ammeter.
Parallel circuit.
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
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?
Imagine your world without electricity: no lights, no television, no central heating, no shower. It would be a strange place.
P8P6
55
Unit 2 Energy and our Universe
Ohm’s lawOhm’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.
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.
Electrical
property
Unit Symbol
Voltage volt V
Current ampere or
amp
A
Resistance ohm (Greek
symbol
omega)
Table: Units and symbols of electrical properties
Worked example
1 What is the voltage across a 300W speaker if the current flowing is 0.01A?
voltage = current × resistance
= 0.01 × 300 = 3V
2 If the voltage across the speaker was 9V, what current would be flowing?
voltage = current × resistance
so current =voltage
resistance
=9
300= 0.03A
Grading tip
Make sure that when you perform
electrical calculations you change the
prefix (e.g. ‘m’ in mA) to numbers.
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.
2 This question uses Ohm’s law. If a resistor in a circuit is 1500Ω,what is the current through it if it is connected across a 1.5Vsupply?
3 Using a circuit diagram, show how you could confirm the current and voltage readings in question 2 by using the correct measuring instruments.
Assessment activity 2.9
Functional skills
Correctly obtaining the value of the current involves identifying the problem and selecting the correct mathematical method.
P6
P6
P8
P8P6
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.
(a)
(b)
56
BTEC’s own resources
2.10 Producing electricalenergy – batteriesIn this section:
You have probably used something powered by a battery today – your alarm clock or watch, mp3 player or a remote control.
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.
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 batteriesA 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 Symbols for (a) a cell and (b) a battery.
P6
Activity A
Write down three appliances you have used today that are powered by batteries. Were the batteries rechargeable or non-rechargeable?
metal or
graphite
cathode
electrolyte
paste
paper or
cardboard
salt bridge
metal (often
zinc) anode
57
Unit 2 Energy and our Universe
Cross-section of a dry cell.
series. It therefore supplies 9V. 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.
Safety and hazards
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.
Activity B
What kind of electricity is produced by a battery? Why does it have this name?
Rechargeable batteriesCells 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.
A rechargeable car battery.
1 Explain the difference between a rechargeable and a non-rechargeable battery. Give five examples of uses of each.
2 Draw a labelled diagram of a primary cell.
3 Discuss with a partner the advantages and disadvantages of rechargeable and non-rechargeable batteries.
Assessment activity 2.10 P6
P6P6
P6
P6
Grading tipTo meet part of the grading criterion for , make sure that you include a diagram for the primary cell. To get all of the criterion you need to also describe another way of generating electricity.
P6
boiler
heat
transformer
cooling tower national grid
turbinegenerator
58
BTEC’s own resources
2.11 Producing electrical energy – non-renewable sourcesIn this section:
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 230V and
the frequency is 50Hz.
Key terms
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 fuelsIn 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 (CO2) is
given off, which is a form of air pollution.
Unit 2: See page 46 for how efficiency is calculated.
Nuclear powerIn 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 CO2 and
is relatively cheap to produce. It does produce radioactive waste.
Producing electricity – ac generatorsElectrical 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).
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.
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.
Electricity generation and distribution.
P6 M4
steady rate of rotation
meter pointer swings
from side to side
alternating
voltageSN
brushesslip rings
coil
dc signal, sign is not
changing direction with time
ac signal, sign is changing
direction with time
Time (s)
Voltage
(V)
A simple ac generator.
59
Unit 2 Energy and our Universe
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.
Output from ac and dc generator.
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.
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.
Assessment activity 2.11
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’.
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.
M4
P6
M4
P6
Activity B
List four ways that alternating current can be increased.
Science snippet
The current produced by an ac generator can be increased by:
using stronger magnetsrotating the coil faster increasing the number of turns of wire on the coilmaking the coil thicker.
60
BTEC’s own resources
2.12 Producing electrical energy – renewable sourcesIn this section:
Transformer – a device that changes the
voltage of an alternating current without
changing its frequency.
Key term
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 powerHydroelectric 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.
Did you know?
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.
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 powerWind 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 powerSolar 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%.
Hydroelectric power stations are expensive to build but cost little to run and do not cause any pollution.
D4M4P7P6
step-up
transformer
consumer
step-down
transformer
25 000V
40 000V
230V
power station
61
Unit 2 Energy and our Universe
The national grid at work, showing transmission lines and transformers.
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 factoriesThe 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 25000V. 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 11000V in some factories.
The voltage from the national grid is reduced using a step-down
transformer.
1 Describe why the voltage used in the home is different from that used to transmit electricity over the national grid.
2 Which equipment is used to increase and decrease the voltage as electricity is transferred from the power station to our homes and factories?
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.
Grading tipFor , ensure that you include each stage of electrical generation. Using a diagram will make your description clear. For 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 remember to include “consumer products” in the discussion. These are products such as TVs, washing machines etc.
Assessment activity 2.12 D4
P7
P7
D4
D4
M4
M4
D4
D4
M4P7
P7
62
BTEC’s own resources
2.13 Understanding our universeIn this section:
Orbit – the path of an object moving
through space, such as the path of the
Earth as it goes round the Sun.
Key term
Stars being born. Each small bulge will eventually form into a collection of planets the size of our Solar System.
The Solar SystemThe 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 skyIf 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.
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 1013 kilometres.
Case study
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?
P9
Sun
Asteroids
Comet
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
63
Unit 2 Energy and our Universe
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 SystemAstronomers 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.
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.
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.
Grading tipFor : When describing the Solar System, make sure you include objects other than planets; there are many other objects out there apart from planets.
Assessment activity 2.13
PLTS
Producing a model of the solar system will develop your creative skills and presenting your work will help you develop team skills.
P9
P9
P9
2.14 Understanding our universe – how did it all happen?
In this section:
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.
Key terms
The Universe is made up of many different objects.
Our Milky Way galaxy: its shape is a spiral and the Sun is near the edge, as shown in this representation.
Our UniverseSo 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.
BTEC’s own resources
64
P10 M5 M6 D5 D6
Unit 2 Energy and our Universe
P10
M6D6
M5 D5
65
Expansion of the UniverseMany 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 theoryAccording 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.
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.
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.
2 Describe the evidence that indicates that the Universe is changing.
3 Describe the strengths and weaknesses of this evidence.
4 Describe the Big Bang theory of how the Universe was formed ; how sure are you that this theory is correct?
Assessment activity 2.14 Grading tip
To obtain , make sure you include
the red shift and the COBE as evidence
that the universe is expanding. In
attempting , remember that you
need to describe how the evidence
you identified for suggests a
changing universe. For you
need to discuss the evidence for and
against stating that the universe
is changing.
D6M5 D5P10 M6
P10
M6
D6P10
Activity B
What does the Doppler effect tell us about our Universe?
Just checking
Assignment tips
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.
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 calcula-
tions 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
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BTEC’s own resources