MODULE mod7A mod7B mod7C mod7D mod7E mod7F mod7G mod7H mod7I mod7J mod7K mod7L mod8A mod8B mod8C mod8D mod8E mod8F mod8G mod8H mod8I mod8J mod8K mod8L mod9A mod9B mod9C mod9D mod9E mod9F mod9G mod9H mod9I mod9J mod9K mod9L 9ia1
9Ia1 Types of energy 1
Name _____________________________ Class ____________
1 Complete the following sentences using some of the words in the box. You may need to use some words more than once.
chemical electrical energy gravitational heat kinetic light
nuclear potential stored strain
a There are many different forms of _________________ . Some forms of energy are
sometimes called energies in action and others are _________________. The proper
name for these energies is _________________ energy.
b A moving car has _________________ energy. It uses _________________ energy
stored in the petrol.
c A car battery contains _________________ energy. The battery helps the car
headlights to give out _________________ energy.
d A diver at the top of a cliff has _________________ potential energy.
e A stretched spring contains _________________ energy.
2
a What form of energy does the CD player give out? _________________
b What do you have to put into the CD player to make it work? ___________________
__________________________________________________________ (not the CD!)
c Which form of energy is stored in these things? _______________________________
[ knowledge, literacy ]
9Ia2 Energy changes
Fill in the table using the words in the box. One has been done for you.
Energy in
Energy out
chemical electrical gravitational potential heat
kinetic light sound strain
[ knowledge ]
9Ia3 Changing energy 1
Fill in the gaps in these sentences, using the words in the box.
1 a When the kettle is switched on the
__________________ energy is
being changed into
__________________ and
__________________ energy.
b When the drill is working the
being changed into _________________ ,
_________________ and heat energy.
c When the gas cooker is on it is changing
__________________ energy stored in the
gas into __________________ ,
__________________ and sound energy.
chemical electrical heat kinetic light sound
2 The pictures below show some objects that need electrical energy to work.
Write the useful energy each object produces in the boxes.
electrical energy
¾¾¾¾¾¾¾¾¾¾¾¾→
9Ia4 Types of energy 2
1 Draw a table with columns for energy in action and stored energy.
Write these words in the correct columns.
chemical electrical gravitational potential
heat kinetic light nuclear sound strain
Look carefully at the picture. Copy the table, and fill it in to show what is happening to the different kinds of energy. One has been done for you.
9Ia5 Changing energy 2
1 Look at the picture. Draw a circle around seven things that need energy to work.
2 Choose five examples from the picture and complete the table below. One example has been done for you.
Object
Form of energy to make it work
Form of energy it produces
3 The pictures below show some objects that need electrical energy to work.
9Ia6 Energy at work
Look carefully at this picture of a garage.
1 Which objects use electrical energy to make them work?
___________________________________________________________________________
2 Fill in this table to show which energies in action the things in the picture give out. The first one has been done for you.
Energy in action
9Ia7 Types of energy 3
1 Look at the pictures below. For each one decide which types of energy are being used or produced. Put a tick in the correct columns. There will be more than one tick for each.
Stored energy
Strain
Gravitational potential
Chemical
Heat
Light
Sound
Kinetic
Electrical
2 Which situation has the most different energy forms?
__________________________________________________________________________________________________________________
9Ia8 Light my fire!
We all need heat energy to stay alive. Humans, like all other mammals, are 'warm-blooded'. This means that our bodies stay at a constant temperature. If we get too cold we can die. Our bodies are normally at 37 °C. If our body temperature goes below 32 °C we lose consciousness, and if it goes below 28 °C we die.
Our bodies produce some heat, and if we lived somewhere warm, we could survive without fire by using animal skins to keep us warm at night. Humans could not live in colder places without fire and clothes to keep us warm. Today in Britain we burn gas or use electricity to heat our homes. In many countries of the world, people still burn coal or wood to supply heat energy. We usually use matches to light fires, but how did people light fires before matches were invented?
One way is to use a flint. This is a special kind of stone that makes a spark when it rubs against a piece of steel. Flints are used to make the sparks in cigarette lighters.
If you haven't got a flint and a piece of steel, you could try rubbing two pieces of dry wood together.
A
B
1 Why do we need fires or other forms of heating? Explain as fully as you can.
2 Name two ways of lighting a fire without using matches.
3 What is the name of the force you get when two surfaces rub together?
4 This force wears things away, but it also produces two forms of energy.
What are they?
5 Pictures A and B show two ways of trying to light a fire using two pieces of wood, but only one of the methods will work. Which one do you think will work? Explain your answer in as much detail as you can.
6 Find out:
a What is a 'tinder box', what did it have in it and why did some people carry them around?
b What are 'flintlocks' and 'matchlocks'?
[ literacy, research ]
9Ib1 Looking at voltage and current
Does the amount of current in a circuit depend on the voltage?
Prediction
The voltage is a way of saying how much the cell or power pack pushes the current.
I think that if the cells or power pack have a higher voltage the current will be
_____________ (bigger/smaller).
Apparatus
- Cells or power pack
- Bulb
- Ammeter
- Voltmeter
- Connecting wires
Method
1 Set up the circuit as shown in the diagram. Ask your teacher to check it.
2 Switch on and read the voltmeter and ammeter. Write the voltage and the current in the results table.
3 Increase the voltage by adding another cell or by changing the setting on the power pack.
4 Read the current and voltage again.
5 Repeat steps 3 and 4 until you have five different sets of readings.
Recording your results
Voltage (V)
Current (A)
Considering your results/conclusion
My results show that if the ______________ of the cell or power pack is ______________
(bigger/smaller) the ______________ in the circuit is ______________ (bigger/smaller).
[ observing, considering ]
9Ib2 Electricity from fruit 1
You can make a very simple cell from two pieces of metal put into a piece of fruit, or dipped into fruit juice.
You are going to investigate which is the best fruit juice to use. You can use a voltmeter to show how good the fruit juice is at making electricity.
- Copper rod - Voltmeter
- Zinc rod - Fruit juices
- Connecting wires - Beaker
- Crocodile clips
Label this diagram using words from the apparatus list.
Fill in the missing words, using words from the box.
beaker copper fruit voltmeter zinc
I will put some fruit juice into a ____________________ .
I will put the ____________________ rod and the ____________________ rod into the fruit juice
I will connect the ends of the wires to the rods and to the ____________________ .
I will write down the voltage in my results table.
I will repeat the investigation with different ____________________ juices.
Fruit juice
Draw a bar chart to show your results.
Considering your results/conclusions
I have found out that the best fruit juice to use is ____________________ .
I know this because the voltmeter gave the ____________________ reading.
[ observing, presenting, considering ]
9Ib3 Electricity from fruit 2
You can make a very simple cell from two pieces of metal put into a piece of fruit, or dipped into fruit juice. You can use a voltmeter to show how good the fruit juice is at making electricity.
You could investigate different fruit juices, or find out which metals work best.
- Metal rods - Voltmeter
- Connecting wires - Fruit juices
- Crocodile clips - Beaker
Planning
1 What are you going to investigate? (Different metals or different fruit juices?)
2 Draw a diagram to show how you will set up your apparatus.
3 Describe how you will carry out your investigation.
4 What will you have to keep the same to make it a fair test?
5 Draw a results table, then carry out your investigation.
6 Draw a bar chart to show your results.
7 Write a conclusion for your investigation that explains what you have found out.
Evaluation
8 Could you improve your investigation if you had time to do it again? Explain how.
[ planning, observing, presenting, considering, evaluating ]
9Ib4 Revising electricity
Cut out the following question and answer cards. Some questions have more than one answer. Find the correct answer cards for each question. Write down the question number and the letter(s) of the answer card (or cards) in your book. You do not need all the answer cards.
---------------------------------------------------------------------------------------------------------
Question cards
1 Choose a parallel circuit.
2 Choose a series circuit.
3 Choose two circuits that have two bulbs controlled by one switch.
4 Choose a circuit with an ammeter in the correct place.
5 Choose two series circuits that have brighter bulbs than this circuit.
6 Choose a circuit that has a dimmer bulb than this one.
7 Why doesn't the bulb light in this circuit?
8 Choose a circuit which has a brighter bulb than this one.
C
D
E
F
G
H
I
J
K
L
M It needs another cell.
N There is a gap in the circuit.
9Ib5 Voltage
This is a 1.5 V cell.
Several cells can be used together to make a battery, like this
When you put cells together like this you get a higher voltage.
1 Copy and complete this table:
Number of 1.5 V cells
Total voltage (V)
1
1.5
3.0
3
4
5
6
2 Draw a bar chart to show how the voltage of a battery changes when you add more cells.
3 Copy and complete these sentences using words from the box.
A cell in a _______________ pushes electrons around the circuit, and it gives the electrons
_______________ . The electrons _______________ this energy to other components, like
_______________ or motors, as they flow around the circuit.
A cell with a high _______________ pushes more _______________ than one with a low
voltage.
Voltage is measured using a _______________ . The units are _______________ .
bulbs circuit electrons energy transfer voltage voltmeter volts
9Ib6 High voltages
Small electrical items like radios or torches do not use up much energy. Cells can be used to supply the electrical energy they need. Other items of electrical equipment, like kettles or washing machines, use up much more energy. They need higher voltages to make them work. Electricity at high voltage comes from the mains supply.
Electricity is sent around the country in overhead wires. The system of wires is called the National Grid. Some of the energy in the electricity is lost as it travels through the wires. To keep these energy losses as small as possible, the electricity is changed to an even higher voltage to go through the wires.
It is very dangerous to touch overhead wires, or the wires above railway lines. If you or a kite string or a fishing rod go near to the wire, large amounts of energy will flow through your body. People who get electric shocks from high voltage electricity supplies often die, or are very badly injured.
1 Write down four electrical items that use cells.
2 Write down four pieces of electrical equipment that need a mains supply.
3 Write down two differences between the electricity obtained from a cell, and the electricity from the mains supply.
4 What is the National Grid?
5 Why is the electricity in the National Grid at a very high voltage?
6 What is a transformer?
7 Why do you think a factory would need a higher voltage electricity supply than a house?
8 Lightning is a form of electricity. Lightning can transfer a lot of energy. Find out how you can keep safe if you are caught outside in a thunderstorm. Write down a set of rules to help someone keep safe, or make a leaflet to explain what to do.
[ literacy, knowledge, research ]
9Ib7 Power
In a circuit, energy is transferred from a cell or a power station to appliances like lights, cookers and TVs. The amount of energy transferred depends on the current and the voltage.
Electrons carry energy around a circuit. If more electrons flow then more energy can be transferred. High currents carry more energy.
The voltage is a way of saying how much energy the electrons are carrying. If there is a high voltage, the electrons are carrying a lot of energy.
A machine transfers electrical energy into other forms of energy. The power of a machine is the amount of energy it transfers every second. A powerful machine transfers a lot of energy each second.
You can work out the power of an electrical appliance using this formula:
power = current × voltage
(W) (A) (V)
The units for power are watts (W) - 1 watt is 1 joule of energy transferred per second.
1 What does power mean?
2 a What are the units for power?
b What does the unit mean?
3 Explain why the power depends on the voltage and the current.
4 Sometimes you might know the voltage and power and need to calculate the current. Rewrite the equation with current on the left-hand side:
current =
5 a Calculate the power of the components in this circuit:
b Why do you only need one ammeter in the circuit?
6 This table shows some facts about various electrical components used in a house. Copy the table and fill in the spaces.
Appliance
Power
(W)
Voltage
(V)
Current
(A)
radio
12
0.052
fan heater
230
8.70
kettle
2400
toaster
770
light bulb
40
0.175
100
outside light
2.17
fridge
0.11
TV
500
0.24
electric oven
2800
electric hob (4 rings)
30.43
7 a What do you notice about the voltages?
b Why do you think this is?
8 Write the items in the table in two lists; one for appliances that are mainly used for heating, and one for those that do other things. Write the power of the appliance next to each one. What do you notice about the power ratings in your two lists?
[ knowledge, numeracy ]
9Ic1 Producing electricity
You can make electricity using a magnet and a coil of wire.
You need a lot of wire and a very strong magnet to make enough electricity to light up a bulb. However, in a school laboratory you can only make a little electricity. You can use a sensitive instrument called a galvanometer to show how much electricity is being made.
Moving the magnet
What happens if:
a the magnet is not moving? ________________________________________________
b the magnet is moved slowly into the coil? ____________________________________
c the magnet is moved quickly into the coil?____________________________________
d the magnet is moved out of the coil?_________________________________________
______________________________________________________________________
Number of coils of wire
What happens if you increase the number of coils of wire?
_______________________________________________________________________________
Direction of movement
a the magnet is moved into the coil? __________________________________________
b the magnet is moved out of the coil? ________________________________________
c the magnet is turned around and moved into the coil? ___________________________
Complete the following sentences.
The amount of electricity produced depends on the ____________________ of wire and on
____________________the magnet is moved.
The direction that the electricity flows depends on which way the magnet is
____________________and which way ____________________ it is held.
9Ic2 Pros and cons cards
Fossil fuels are non-renewable.
Nuclear fuels do not produce carbon dioxide.
The wind is a renewable source of energy.
Lots of wave-powered generators would be needed. They might get in the way of ships.
Wind turbines can only be built in certain places.
Nuclear fuels produce radioactive waste that is difficult to get rid of.
The land under wind turbines can still be used for farming.
Burning fossil fuels adds carbon dioxide to the atmosphere.
Hydroelectricity needs reservoirs that flood large areas of land.
Nuclear fuel is non-renewable and expensive.
Tidal power only works on rivers where the water level changes by a large amount.
Lots of wind turbines are needed to produce useful amounts of electricity.
Solar cells only work when it is sunny.
Burning fossil fuels can cause acid rain.
Solar cells take up a lot of space.
Some people do not like to see wind turbines in the countryside.
Wave-powered generators do not produce very much electricity.
Solar cells are expensive and do not collect very much energy.
A tidal barrage would change the environment upstream, and could affect plants and animals that live in the river or near the river.
Wave-powered generators do not work in calm water.
9Ic3 The National Grid
1 Cut out the jigsaw pieces below and assemble them in your book.
2 Use a coloured pencil to join up the letters in alphabetical order.
3 Label your coloured line 'overhead cables'.
4 Use a different colour to go over the dotted lines. Label this 'underground cables'.
Answer these questions in your book.
5 What do transformers do?
6 Why do you think light industry and heavy industry use different voltages?
7 List all the voltages of the electricity between the power station and the houses.
8 Design a poster or a leaflet explaining to young children why they must never go into an electricity substation.
9Ic4 Electricity questions
Some of the answers to these questions are shown jumbled up in brackets at the end of the question.
1 Electricity is made by __________________ it in a __________________
__________________ . (gneretangi, rewop, sttnoia)
2 Name three fuels that can be used in a power station. __________________
__________________ __________________
3 Most fuels in a power station are used to heat water and turn it to __________________ .
(meats)
4 What are the enormous fans in a power station called? __________________ (tenisrub)
5 The generators contain large magnets inside coils of wire. This is because a moving magnet
inside a coil of wire creates __________________ . (eelcitycrit)
6 Where does the electricity from the power station go? __________________
__________________ (tannoila, ridg)
7 What do we call the electricity which comes to our homes? __________________
___________________ (smian, eelcctiirty)
8 Give two examples of using cells. _______________________________________________
__________________________________________________________________________
9 The power rating of an appliance tells you how many ______________ of energy it uses each
______________ . (lojues, descon)
9Ic5 Energy survey
Write down for how long each type of electrical equipment is used in your home each day. You may need to ask an adult to help you. If your home has any pieces of equipment not in the table, write them in the rows at the bottom of the table.
Equipment
Time used per day (minutes)
radio/CD player
computer
video/DVD
microwave oven
hairdryer
dishwasher
lights
washing machine
tumble dryer
vacuum cleaner
iron
immersion heater
[ observing ]
9Ic6 Commercial break
It's the big match - the World Cup final!
All over Britain, millions of people are watching the match. Suddenly the whistle blows - it's half time! All over the country people decide to have a cup of tea, and go and turn the kettle on. All of a sudden the country needs an extra 1 500 000 000J of energy each second!
That's a lot of extra energy. The generators in power stations are huge machines, and it is difficult to start and stop them suddenly. Engineers in power stations need to know how much electricity will be needed ahead of time, so they can make sure there is enough electricity available.
This sudden increase in the demand for electricity is called a 'TV pickup'. TV pickups happen at the ends of programmes, or during commercial breaks when the adverts come on. If it has got dark while people have been watching TV, they also put lights on when the programme ends.
1 What is a 'TV pickup'?
2 Why do engineers need to know that a TV pickup will happen?
3 Which do you think causes the highest demand for electricity: people switching on lights, or people switching on kettles? Explain your answer.
4 This graph shows the demand for electricity during a World Cup match.
Why do you think there was a bigger rise in demand after the penalty shoot-out than there was at half-time?
5 Power engineers use weather forecasts to help them to predict how much electricity will be needed. How do you think the weather can affect the demand for electricity?
9Ic7 Pumped storage
The demand for electricity varies between summer and winter, and at different times of the day. During the day, when people are at work, and in the early evening, the country needs lots of electricity. All the output of the power stations in the country is used. At night, when most people are asleep, not as much electricity is needed.
Sudden changes in demand can cause problems for power engineers. It is not easy to suddenly change the amount of electricity generated by most large power stations. This can result in too much electricity being generated at night, because it is more efficient to leave the power stations running at full capacity than it is to shut them down for the night. Hydroelectric power stations are the only ones that can respond very quickly to changes in demand.
Spare electricity cannot be stored. However, if power stations are producing more energy than consumers need, the energy in the electricity can be stored. Dinorwic power station is in the Welsh mountains. It is a hydroelectric power station, but one with a difference! It has a storage lake at the bottom as well as at the top.
At night, pumped storage power stations like Dinorwic use the spare electricity generated by normal fossil fuel and nuclear power stations to pump water from the bottom lake up to the top one. Electrical energy is being converted into gravitational potential energy. During the day, when there is a sudden rise in demand for electricity, the water is allowed to run down the pipes again, and the stored potential energy is converted back into electrical energy.
1 Why does the demand for electricity change during the day?
2 Why do power stations still produce lots of electricity at night?
3 What is a hydroelectric power station?
4 How is Dinorwic different to a normal hydroelectric power station?
5 Draw two energy flow diagrams; one to show the energy changes at Dinorwic during the day, and one to show what happens at night.
6 What environmental effects do you think a pumped storage power station would have?
[ literacy, knowledge ]
9Id1 Energy dominoes
What is the correct name for movement energy?
Conduction.
What is the form of energy that objects in high positions have?
230 V
Name three things that have stored chemical energy.
Chemical energy.
Heat energy can be transferred through solid objects. What is the name of this process?
Chemical to electrical to light and heat.
Name three fossil fuels.
Electricity generated using the energy in falling water.
Name two sources of energy that do not come from the Sun.
Anything that changes energy.
What is the name for the way heat energy is transferred through empty space?
Convection.
What is the machine in a power station that changes kinetic energy into electrical energy?
Devices that convert light energy into electrical energy.
What is a machine?
Coal, oil and gas.
How do you measure the amount of energy used by a component in a circuit?
Food, cells, petrol.
What is the name for energy stored in a stretched spring?
Generator.
What are the units for measuring energy?
Geothermal and nuclear.
What is the name for the way heat energy is transferred through liquids and gases?
Gravitational potential energy.
What does a cell do?What does a cell do?
Heat and sound.
What kind of energy is stored in a cell?
It has to be generated using other energy resources.
Which materials are good conductors of heat and electricity?
Joules.
Name three sources of renewable energy.
Kinetic energy.
What energy changes happen inside a torch?
Metals.
What is hydroelectricity?
They are
non-renewable fuels, which cause pollution when they are burnt.
What are solar cells?
Nuclear energy.
What is the voltage of mains electricity?
Nuclear fuels do not contribute to global warming.
Pushes the current, and gives it energy.
Name two disadvantages of using fossil fuels to generate electricity.
Radiation.
Name two materials that do not conduct heat very well.
Strain energy.
Name one disadvantage of using wind turbines to generate electricity.
The amount of useful energy that a machine converts.
What does efficiency mean?
The remains of plants.
What kind of energy is stored inside atoms?
They only work when the wind conditions are right.
Name one advantage of using nuclear fuel to generate electricity.
Use a voltmeter.
What kinds of wasted energy does a car produce?
Wind, waves, solar.
Why isn't electricity a source of energy?
Wood and plastic.
9Id2 Wasted energy 1
1 What kind of energy does food supply? ___________________ (calichem)
2 Fill in the missing words on this energy flow diagram:
3 A light bulb changes ___________________ energy into ___________________ and
___________________ energy. (eerltailcc, taeh, ghtli)
The ___________________ energy is useful energy, and the heat energy is
___________________ energy. (tglih, sedwat)
4 Fill in the missing words on this energy flow diagram:
5 What force causes a car engine to get hot? ___________________ (noitfric)
6 A car wastes 75% of its energy. How efficient is it? ___________________
9Id3 Wasted energy 2
1 What kind of energy does food supply?
2 Copy this energy flow diagram and fill in the missing words.
3 a What form of energy does a light bulb use?
b Which two forms of energy does it produce?
c Which of these is wasted energy?
d A light bulb wastes about 85% of its energy. How efficient is it?
e Draw an energy flow diagram for the light bulb (like the one for the runner).
4 a What causes a car engine to get hot? (Hint: There are two reasons.)
b A car wastes 75% of its energy. How efficient is it?
10% efficient.
90% efficient.
5 a Which engine is most efficient?
b Which engine wastes the most energy?
c Where does the steam locomotive get its energy from?
d Where did this energy come from originally? Explain your answer.
6 Look at the efficiency for the electric locomotive.
a Do you think any energy was wasted when the electricity was generated?
b Is its efficiency really 90% if you think about the source of the energy? Explain your answer.
9Id4 Efficient cars
Most cars use engines that run on petrol or diesel. These cars waste 75% of the energy in the fuel, and produce waste gases that cause global warming and pollution. Car manufacturers are working to develop more efficient engines, but they will only be able to change the efficiency by a few percent.
Many people think that we should use electric cars. Electric motors are quieter, and only waste about 25% of the energy they use, so they should help us to save energy resources. At present, special batteries for cars take a long time to charge and cannot store enough energy for cars to travel long distances, but it should not be long before better batteries are developed.
But where does the energy come from that charges up the battery? The electricity has to be generated in a power station. Most power stations burn fossil fuels, and waste about 70% of the energy they use. However, it may be possible in the future to generate more electricity using renewable resources.
1 Write down two advantages of using electrically powered cars.
2 a How efficient is a normal car engine? (Hint: What percentage of energy is converted into useful energy?)
b Imagine that you start with 100J of energy stored as chemical energy in the fuel in a car. How much of this energy will be converted to useful kinetic energy?
3 a How efficient is a power station?
b If you started with 100J of energy in the fuel for a power station, how much useful electrical energy would it produce?
4 How efficient is an electric car, if you include generating electricity at a power station? (Hint: An electric motor is 75% efficient. Multiply your answer to 3b by 0.75 to give you the overall efficiency.)
5 Which is truly the most efficient: an electric car or a normal car?
Electric cars do not have to use batteries. A fuel cell can use hydrogen and oxygen to produce electricity, and is very efficient. The only substance that fuel cells give out is water (formed from the hydrogen and oxygen) so they do not cause pollution. Oxygen and hydrogen can be made from water by electrolysis, so electricity must be generated to get the hydrogen and oxygen for the fuel cell. Using fuel cells will only help the environment and save energy resources if renewable resources can be used to generate this electricity.
A lot of energy is used when cars are made. It takes about 10 times as much energy to make a new car as the car will use up in fuel.
6 Why does a car that runs on fuel cells only have a similar overall efficiency to a car that runs on petrol?
7 Your uncle is thinking of buying a new car that is more efficient, so he will save energy. Write a letter to him, explaining why it might be more efficient to keep the car he has.
[ literacy, numeracy, knowledge ]
9Id5 Wasted energy in a power station
When fossil fuels are burnt in a power station a lot of energy is wasted. In a coal-fired power station, energy is only useful when it moves from the heat of the burning coal to the kinetic energy of the turbines. As these changes take place some of the energy is wasted because it is lost as heat to the surroundings.
Energy is measured in joules. In a power station large amounts of energy are involved so it is measured in megajoules (MJ). One megajoule is a million joules (1 000 000 J).
1 Copy the table, and use information from the diagram to fill it in.
A Energy is supplied from the fuel
B Some energy is lost as fristion in the turbines
C A lot of energy is lost in cooling the water and given off to the air as heat
D Some energy is lost in heating the wires
Section of power station
Reason for energy loss
Amount of energy loss in MJ
Total energy lost =
2 What does MJ stand for?
3 How many joules are in a megajoule?
4 a How much total energy is wasted for every 1000 MJ in the fuel?
b What percentage is this of the whole?
5 a How much usable energy is produced from 1000 MJ of coal?
6 What is the efficiency of the power station?
9Id6 Energy-saving bulbs
Energy-saving bulbs cost less to run, but they cost more to buy. Do you really save money by buying the energy-saving bulbs? Find out by answering the questions.
1 How much energy would the energy-saving bulb use in its lifetime? (Hint: 1 W = 1 J/s.)
2 How much would this energy cost?
3 What is the total cost of using this bulb for its lifetime?
4 How much energy does the normal filament bulb use during its lifetime?
5 How much would this energy cost?
6 What is the total cost of using this bulb for its lifetime?
7 You need to buy more normal bulbs, because they do not last as long. How much would you have to spend to get the same amount of light as an energy-saving bulb would give you?
8 Give two reasons why energy-saving bulbs are cheaper than normal filament bulbs.
[ numeracy ]
9I Summary Sheets
Energy and electricity
Nothing would happen without energy. Energy is needed to:
- keep our bodies working
- make machines work
- heat homes, schools and offices.
Energies in action
- heat energy
- light energy
- sound energy
- electrical energy
- kinetic (movement) energy.
Some energy has to be stored so that it is ready for use when we need it.
- Chemical energy is stored in food, fuels and cells.
- Gravitational potential energy is stored in high up things.
- Strain energy is stored in stretched or squashed things.
- Nuclear energy is stored inside atoms.
How is energy measured?
Energy is measured in joules (J) or kilojoules (kJ). A kilojoule is 1000 joules.
Energy changes
Energy needs to be changed to be useful.
in the cells in the wires in the bulb
and bulb
An energy flow diagram.
Many energy changes take place in everyday life. Often wasted energy is produced in the forms of heat or sound.
A car engine produces kinetic energy, which is useful. It also produces heat and sound
Energy cannot be made or destroyed, but can only be changed from one form to another. This is the law of conservation of energy.
A circuit must have a cell or power supply to provide a voltage. The voltage pushes the electrons around the circuit and gives them energy. This electrical energy is transferred to other components in the circuit, which convert it to other forms of energy. For instance, a light bulb transfers electrical energy to heat and light energy.
The voltage of a cell can be measured using a voltmeter. The units for voltage are volts (V).The voltage across a component is a way of measuring how much energy the component is transferring. The voltage across all the components in a series circuit adds up to the voltage across the cell.
Electricity and cells
Electricity is supplied to homes and factories as mains electricity. This travels along cables connected to the National Grid.
Generating electricity
Fossil fuels are transported to power stations where they are burnt to release heat energy. This heats water, turning it to steam. The steam drives turbines which turn generators. The electricity generated flows along cables into the National Grid.
Nuclear fuel is made from a radioactive metal called uranium. The energy in nuclear fuel did not come from the Sun.
Electricity can be generated from renewable resources such as wind and moving water. These will become more important as fossil fuels run out.
Sometimes we need a source of portable electricity when we are not close to the mains. This can be supplied by cells (sometimes called batteries). These store chemical energy which can be changed to electrical energy. Cells go flat when they run out of chemical energy. Some cells can be recharged.
Wasting energy
Energy cannot be made or destroyed, but it can be changed to different forms. Not all energy is turned into a form that we want. Often it is turned into heat that we do not need. This is wasted energy. A car engine produces kinetic energy, which is useful. It also produces heat and sound which are wasted forms of energy.
The percentage of useful energy produced by something is known as its efficiency. The human body is 25% efficient.
9I Target Sheet
Topic
Targets
Before the unit
I have learned this
I have revised this
9Ia
Know the different forms of energy.
Know the different ways that energy can be stored.
Be able to give some examples of energy changes.
Know what a machine is.
9Ib
Know the units for measuring voltage.
Know how to measure voltage.
Know what voltage is.
Know what happens to the voltage in circuits.
9Ic
Know where electricity is made and how it gets to our homes.
Know that electricity is made using other energy resources.
Know what an electrical cell is.
Know some of the dangers of high voltages.
9Id
Know the law of conservation of energy.
Be able to draw an energy flow diagram.
Know which forms of energy are usually produced as waste energy.
Know what efficiency means.
9I Word Sheets
Word sheets that include new words from the 'Focus on:' pages are available on the Exploring Science website.
9Ia - The energy exchange
Word
Pronunciation
Meaning
atomic energy
Another name for nuclear energy.
cell
sell
It contains a store of chemical energy that can produce electricity (the scientific name for a battery).
chemical energy
The kind of energy stored in chemicals. Food, fuel and cells (batteries) all contain chemical energy.
The kind of energy carried by electricity.
energy flow diagram
A way of showing energy changes as a flow chart.
gravitational
grav-it-ay-shon-al
The kind of energy stored by anything that can fall down.
potential energy
heat energy
po-ten-shall
The hotter something is the more heat energy it has.
joule (J)
jool
The unit for measuring energy.
kilojoule (kJ)
kill-o-jool
There are 1000 joules (J) in 1 kilojoule (kJ).
kinetic energy
kin-et-ick
The kind of energy in moving things.
light energy
The kind of energy given out by light bulbs, candles, etc.
machine
Something that changes energy from one form to another.
nuclear energy
Energy stored inside atoms.
The scientific word for 'stored' energy.
sound energy
The kind of energy that is made by anything that is making a noise.
strain energy
The kind of energy stored in stretched or squashed things which can change back to their original shapes.
transfer
When energy is changed from one form into another we say it is transferred.
9Ib - Pushing the current/Portable energy
ammeter
Measures how much electricity is flowing around a circuit.
current
The flow of electrons around a circuit.
electron
Tiny particle that flows around a circuit.
in parallel
A circuit is in parallel when the current divides, a part going through each component, then joins up to complete the circuit.
model
A scientific way of thinking about how things happen.
rechargeable
ree-charge-ab-el
Cells that can have more energy stored in them after they have been used are said to be rechargeable.
resistor
A component that makes it more difficult for current to flow - resistors are used to control the size of the current in the circuit.
voltage
A way of saying how much energy is transferred by electricity.
voltmeter
A component that measures voltage.
volt (V)
The unit for voltage.
9Ic - The mains supply/The generation game
generate
Make electricity by turning a magnet inside coils of wire.
generator
Large coil of wire with a magnet inside. When the magnet is turned, electricity is produced in the coil of wire.
kilowatts
There are 1000 watts (W) in 1 kilowatt (kW).
mains electricity
Alternating current at 230 V provided to houses, shops, etc.
National Grid
System of overhead and underground cables that carry electricity around the country.
power rating
The number of joules of energy an appliance uses every second.
turbine
A machine that is turned by a moving liquid or gas. Turbines are used to turn generators in power stations.
watt (W)
The unit for measuring power. One watt is one joule per second.
9Id - Wasted energy
efficiency
e-fish-en-see
A way of saying how much energy something wastes.
law of conservation
The idea that energy can never be created or destroyed, only changed from one form of energy to another.
wasted energy
Energy that is not useful.