2018_SCIENCE Teacher

9 10 Unit 7 - Transformation of Energy
8
Activity 7.2 What is energy transformation?
7
6
5
4
3
2
1
0

mber Think What is energy transformation?
and think Is energy transformation important in our everyday life?

Discuss and find out some activities that we cannot do without
energy transformation.

Energy exists in various forms. List them.

________________________________________________________________________

_________________________________________________________________________

Energy transformation is the process by which one form of energy is changed into
another form (or forms) of energy.

We can use a simple diagram to describe an example of energy transformation. The diagram
below shows how one form of energy is transformed into TWO forms of energy.

Example: Chemical energy is changed into light and heat energy.

Chemical energy light energy
heat energy

The diagram below shows how one form of energy is transformed into THREE forms of ener-
gy.

Example: Chemical energy is changed into electrical energy which is then changed into
light, heat and sound energy.

Light Energy

Chemical Energy Electrical Energy Heat Energy

Sound energy

91

Unit 7 - Transformation of Energy

Did you know?

Energy is also transformed from one form to another in the human body.
The food that we eat contains chemical energy.
This energy is transformed into:
1. movement energy for our activities
2. heat energy to keep our body warm

Even animals use the energy from food to move from one place to another.
Draw a diagram of the energy transformation for the flying bird.

A bird flying

92

Unit 7 - Transformation of Energy

Draw a diagram of the energy transformation for the chirping bird.

A chirping bird

What is the energy transformation in a car?

In cars, the chemical energy stored in petrol is converted
into movement energy.
Part of this chemical energy is also transformed into electrical energy.
This electrical energy is then transformed into light energy in the headlights and sound energy
in the speakers and the car horn.
Using the information above, draw a diagram to show the energy transformation in a car.

headlights horn in a car

A horn is a device
that makes a loud
sound in a car.

Find Find out where the speakers are found in a car.
out

93

Unit 7 - Transformation of Energy

Teacher’s note pg 95

Activity 7.3 Transformations of energy in everyday life
Learning outcomes:
By the end of the activity, pupils should be able to:
• Demonstrate understanding of the activities shown in each picture
• Identify the forms of energy shown in various contexts/pictures
• State the energy transformations taking place in these contexts/pictures
Skills: observing pictures, communication of information obtained from pictures given, literacy
This activity is about observing some pictures given, identifying the activity in the pictures, and then
expressing the energy transformations taking place using the right terms.
1. For washing the car, chemical energy of the person is converted into movement energy.
2. When drilling a hole in the wall using an electric drill, electrical energy is mainly converted into
movement energy. We also obtain sound and heat energy but these are not useful.
3. Charcoal stores chemical energy. When charcoal is burnt, chemical energy is mainly transformed
into heat energy. Some light energy is also produced. The heat energy is used to grill or cook food.
4. A street lamp uses electrical energy to function. The electrical energy is converted to light energy
in the bulb. We also get some heat energy that is not useful in the street lamp.

94

Unit 7 - Transformation of Energy

9 10
8

7 Activity 7.3 Transformations of energy in everyday life
6
5For the examples shown, describe the energy transformation using a simple diagram.
4The first one is done for you.
3
2
1
0

1. Washing a car movement energy
chemical energy

2. Drilling a hole in the wall.

3. Burning charcoal.
4. Lighting an electrical street lamp.

95

Unit 7 - Transformation of Energy

Teacher’s note pg 97-98

Activity 7.4 Using heat energy from the Sun

Learning outcomes:
By the end of the activity, pupils should be able to:
• Demonstrate understanding of different ways in which water is heated at home
• State that heat from the Sun can be used to heat water
• Recognise a solar water heater
• Explain the energy conversion in a solar water heater

Skills: observing pictures, communication of information obtained from pictures, literacy, social

This activity is about the use of heat energy obtained from the sun.
Pupils will work in groups to find out what are the different ways in which we obtain hot water at
home. They will then communicate their findings. They will state that one way to obtain hot water
is by using the electric kettle and another way is by using a gas stove or wood stove.
Other possible ways suggested by pupils could be by the use of:
• Gas water heaters
• Solar water heaters
• Exposing the water in sunlight for some hours during the day
• Using electric coil heater and so on
Then the teacher stresses on the fact that the heat energy obtained from the sun can also be used
to heat water at home and that many people get hot water through this means.

The diagram of a solar water heater is shown and discussed. Through discussions, pupils are taught
that energy from the sun is used to heat water at home, at school and in offices.
The energy transformation is stated as follows:
Heat energy from the Sun is transformed into heat energy of the water.
The question that the teacher will ask for further discussion is ‘Where is this heater usually placed in
the house?’
Pupils will discuss and state that the solar water heater is always placed on the roof. The reason to
do so is that there is less shadow on the roof than on the ground.
Another question for discussion is asked as to why in winter solar water heaters cannot heat water
properly. After discussion pupils are made to understand that in winter the sun shines less brightly.
There is less heat energy obtained from the sun by the water. So the extent of heating is less. We
can also discuss about the temperature of air being low in winter, so the hot water cools down.
Pupils are also required to discuss in groups about the advantage of using heat energy from the
sun. Several answers are possible. Pupils may suggest that energy from the sun is free, we do not
spend money to obtain it. Some pupils may also state that energy obtained from the sun does not
cause pollution.

Thus, from this activity, pupils would learn that hot water can be obtained at home by different
means. The heat energy from the sun can be used to heat water directly. The source of energy is
free of cost and it does not cause pollution.
Pupils are also involved in discussion on why people prefer to use energy from the sun rather than
fossil fuels. After discussion and further research, pupils come up with the idea of the cost involved
in the acquisition and use of fossil fuels and also pollution caused by the use of fossil fuels.

96

9 10 Unit 7 - Transformation of Energy
8
Activity 7.4 Using heat energy from the Sun
7
6 How do we get hot water at home?
5
41. List TWO more ways by which we can get hot water at home.(one example is given)
3a. By heating water in an electric kettle.
2b. ____________________________
1c. ____________________________
0
Did you know?

We use the heat energy of the sun to get hot water in many homes.

The figure shows one type of solar water heater.
In the solar water heater, the heat energy of the
Sun is used to heat water.
A solar water heater
2. Describe the energy transformation for the solar water heater.

97

Unit 7 - Transformation of Energy

3. Where is the solar heater usually placed in the house?
______________________________________________________________________

4. Why?
______________________________________________________________________

5. People who use solar water heaters often cannot get hot water in winter. Why?
______________________________________________________________________

6. State ONE advantage of using heat energy obtained from the Sun.
______________________________________________________________________

What I have learnt

• There are many ways in which we can heat water at home.
• The heat energy from the Sun can be used directly to heat water.
• The solar water heater helps us to save a lot of energy.
• Heat energy from the Sun can be used instead of fossil fuels such as natural gas.

Think Why do most people prefer using energy from the sun rather than fossil
and think fuels?

98

Unit 7 - Transformation of Energy

Teacher’s note pg 100-101

Activity 7.5 Using light energy from the Sun

Learning outcomes:
By the end of the activity, pupils should be able to:
• Demonstrate understanding of different ways in which light energy from the Sun can be used
• Recognise a solar water panel placed on buildings
• Explain the energy conversion in a solar panel

Skills: observing pictures, communication of information obtained from pictures, literacy, social,
higher order thinking

This activity is about the conversion of light energy from the sun into electrical energy. This electrical

energy can be used in various ways such as in solar calculators and solar street lamps.

The electrical energy is obtained through the use of a large number of cells that are placed on the

solar panels. These cells are called photovoltaic cells or simply photocells. These panels are kept

on buildings in an inclined position so that sunlight can strike them throughout the day. Thus, light

energy is converted into electrical energy. Given that the electrical energy obtained from a single

cell is small, a large number of cells are connected on the solar panel to obtain a reasonable

amount of electrical energy for various uses. At home, the electrical energy obtained from the

solar panels can be used for lighting of lamps, for operating computers and charging mobile

phones. This can be shown diagrammatically as below.

Chemical energy (in mobile phone)

Light energy electrical energy Movement energy (in fan)

Light energy (in bulbs)

The section on ‘Did you know?’ focusses on the MCB (Mauritius Commercial Bank) building situated
at Ebène. It makes use of a large number of solar cells fixed on panels. The electrical energy
obtained is used for lighting, operating computers and other things.

Solar calculator
The solar calculator has a small number of solar cells. In this picture there are five.
The energy transformation is:
Light energy from the sun to electrical energy in the calculator and then to light energy in its
screen. Some of the calculators also produce a beep sound when the keys are touched. Thus, we
may also have electrical energy being transformed into sound energy in the calculator.

Street lamp
The picture shows a street lamp which also has two solar panels. In the solar panels there are solar
cells.
During the day, light energy is converted into electrical energy. This electrical energy is converted
into chemical energy inside a battery that is connected to the panels. The battery is charged by
the electrical energy.
The energy conversion during the day is:
Light energy to electrical energy (in the cell) to chemical energy (in the battery)
At night, the solar panels cannot function as there is no light energy from the sun falling on them.
So the chemical energy stored in the battery is used to light the bulbs.
The energy conversion at night is:
Chemical energy (in the battery) to electrical energy (in the wires) to light energy in the bulb.

99

Unit 7 - Transformation of Energy

9 10
8

7 Activity 7.5 Using light energy from the Sun
6
5
4
3
2
1
0

Solar panels A panel is a flat
board.
Light energy from the Sun can be used in many ways:
1. Many houses have solar panels on the roof.
2. Solar calculators use light energy to work.
3. Some street lamps use light energy from the Sun.

Solar panels contain solar cells.

When the light energy from the
Sun falls on the solar cells, the light
energy is transformed into electrical
energy. This electrical energy is then
transformed to other forms of energy.

solar panels
Complete the diagram below to show how we can use solar energy at home.

light energy

Did you know?

Do you recognise this building? ___________

Do you know that this building has a large number
of solar panels?

Can you see them now?

Solar panels are large and flat.
100

Unit 7 - Transformation of Energy

Solar Calculator solar cells

A solar calculator has solar cells as shown.

Describe the transformation of energy as light falls on the solar cells.

__________________________________________________________

Street Lamp
The picture shows a street lamp.
Draw an arrow to show the solar panel. Label it.
Let us see what happens during the day and at night.

During the day:
Explain how the solar cells transform energy.
__________________________________________________________________________
Draw a diagram to show this energy transformation.

The lamp has rechargeable batteries. The electrical energy produced during the day charges
the batteries.

Draw a diagram to show this energy transformation.

During the night:
At night, the energy stored in the batteries is transformed to light energy.

Draw a diagram to show this energy transformation.

101

Unit 7 - Transformation of Energy

Teacher’s note pg 103

Activity 7.6 Transformations of energy in simple devices
Learning outcomes:
By the end of the activity, pupils should be able to:
• Identify the contexts given in terms of the pictures
• Name the simple devices shown
• Discuss the energy conversions taking place in each context
• Express the energy conversions taking place in each context
Skills: observing pictures, communication of information obtained from pictures, literacy, social,
higher order thinking
This activity is about the conversion of energy in simple devices. The focus is on the initial form of
energy and the final form that is obtained, though there may be some intermediate stages with
other forms of energy.
Pupils will discuss in groups and are expected to provide the following answers:
1. A radio set
Chemical energy to sound energy
If more detailed discussion occurs, pupils may say that it is chemical to electrical and then sound;
at a still higher level, we may say it is chemical to electrical to movement (in the speaker) and then
sound. But at standard V level, only the initial and the final energies may be considered.
2. An electric fan
Electrical energy to movement energy (anything that is moving in a straight line or oscillating or
rotating or turning, has movement energy.
3. A moving car
Chemical energy to movement energy
4. A gas stove
Chemical energy to heat energy (we also get light energy but the useful energy is heat)

102

Unit 7 - Transformation of Energy

9 10
8

7 Activity 7.6 Transformations of energy in simple devices
6
5
4
3
2
1
0

Using a diagram, state the energy transformation in each of the following devices. One
example is given.

1. A radio set that uses cells

chemical energy sound energy

2. An electric fan

3. A moving car

4. A gas stove

103

Unit 7 - Transformation of Energy

Teacher’s note pg 106-107

Activity 7.7 Conserving energy

Learning outcomes:
By the end of the activity, pupils should be able to:
• Identify and name situations and examples where energy is wasted
• State few measures taken to save energy
• Adopt appropriate attitude towards saving energy

Skills: comparing, observing, communication, literacy, social, higher order thinking

In this activity, pupils will discuss in groups on various examples where there is wastage of energy.
They will also suggest ways in which energy conservation can be achieved. Through the examples
they will discuss, they will be taught to adopt appropriate attitude towards energy saving.
The first example is showing a room where several lamps are on but there is nobody in that room.
Thus energy is being wasted as the light is not needed there. In order to save energy, all the lights
need to be put off or at least one dim light should be on.
In the second example, the girl has taken out a drink from the refrigerator and is walking away
without closing the door of the refrigerator. In this way energy is wasted because warm air has
entered the refrigerator. The appropriate habit is to keep the door closed all the time. If we need
to open it to remove or keep something, it needs to be closed immediately.
In the next example, a person is listening to very loud music. This is showing a waste of energy as
loud sound is equivalent to more electrical energy being used. The energy saving measure is to
listen to soft music.
In the fourth example, the boy is leaving the room but the television set is on. This is wastage of
energy because the TV set is using electrical energy while nobody is watching. The appropriate
habit is to switch off the TV set while leaving the room if nobody is watching.

The activity continues with additional examples of saving energy.
In the first example, the boy is switching the TV off before leaving the room. This practice saves
energy and it is a simple step for pupils to follow as well as for adults.

In the second example, the boy has opened the refrigerator but is concentrating on his mobile
phone. This is a bad practice as energy is wasted when warm air enters the refrigerator. The latter
has to spend more electrical energy to cool the warm air that has entered.

In the third example, the man is keeping warm food in the refrigerator. This is a bad practice
because the refrigerator has to spend more electrical energy to cool the warm food. It is better to
allow the food to cool down and then to put it in the refrigerator.

In the fourth example, the lady is putting clothes in the washing machine. She is putting a full load.
This means she is putting the maximum quantity that is washable. In this way she will not have to
wash several times as this practice wastes electrical energy.

104

Unit 7 - Transformation of Energy

Teacher’s note pg 108-109

Activity 7.8 Understanding energy-efficient bulbs
Learning outcomes:
By the end of the activity, pupils should be able to:
• Give reasons why we must save energy
• Observe ordinary and energy-efficient bulbs
• Explain why we need to replace ordinary bulbs by energy-efficient ones
• State how energy is saved when using energy-efficient bulbs
Skills: observing, comparing, communication, literacy, social
In this activity, pupils will discuss in groups about the use of normal bulbs (also called filament bulbs)
and energy-efficient bulbs. The way in which energy is saved by using the latter is explained.
Two reasons why we must save energy:
• Wasting energy means wasting money and we cannot afford to waste money.
• Saving energy is also related to keeping our environment clean
In this part of the activity, pupils will discuss in groups and decide on the one that is the energy-
efficient and the one that is the normal filament one. (the word ‘filament’ may be explained to
pupils and a concrete example of a bulb shown to them).
The ordinary bulb with the filament is crossed, whereas the energy-efficient bulb is circled by pupils,
after group discussion.
Pupils may be explained that normal (filament) bulbs produce a lot of heat energy unnecessarily
and energy is wasted, whereas, the energy-efficiency bulbs produce less heat and more light, so
it is economical. When we use energy-efficient bulbs energy is saved.
The ‘Did you know?’ section consolidates the ideas learnt earlier on saving energy. It provides
a simple way to conserve or save energy that is switching off all lights in a room when nobody is
present there. This is normally done by the last person leaving the room.
Saving of energy is related to combatting global warming. Global warming causes the sea level
to rise and all the related problems. Pupils will study about this later. At this stage pupils are taught
how and why to save energy.

105

9 10Unit 7 - Transformation of Energy
8
Activity 7.7 Conserving energy
7
6Energy is precious. Everyday we use energy for many purposes. We obtain this energy from
5many sources.
4In this activity, we will discuss the ways in which energy is wasted at home and how we can
3avoid wasting it. The diagrams below show some bad practices in using energy at home.
2For the examples given, write a sentence to show how:
1(i) energy is wasted.
0(ii) we can avoid wasting this energy.
One example is given.

(i) Many bulbs have been left on in the living room.
(ii) We must switch off all lights and appliances if

we do not need them.

(i)
(ii)

(i)
(ii)

(i)
(ii)

106

Unit 7 - Transformation of Energy

Examples of wasting and saving energy

Are there other ways of saving energy? Let us find out.

Raj is switching off the TV when not watching.
This saves energy.

Sam opens the refrigerator unnecessarily.
This wastes energy.

Father keeps warm food in the refrigerator.
This wastes energy.

Mother puts full load in washing machine.
This saves energy.

107

9 10Unit 7 - Transformation of Energy
8
I conclude from my observations
7
6 There are many ways in which we waste energy at home. We waste energy by:
51. Leaving lights on in a room when they are not needed.
42. Leaving TV set on when nobody is watching it.
33. Opening the refrigerator unnecessarily.
2
1 Activity 7.8 Understanding energy-efficient bulbs
0
Give TWO reasons why we must save energy.
1.____________________________________________________________________
2.____________________________________________________________________
There are different types of bulbs that people use.

Have you seen these types of bulbs? _________
Cross the ordinary bulb.
Circle the energy-efficient bulb.

Question

We should replace ordinary bulbs by energy-efficient bulbs. Explain why.
__________________________________________________________________
__________________________________________________________________

Energy-efficient bulbs are light
bulbs that use less electrical
energy and can last longer
than ordinary bulbs.
108

Unit 7 - Transformation of Energy

Did you know?

To get energy continuously at home and school we spend a lot of money. If we waste
energy, it means we are wasting money.
So we need to avoid wasting energy. This is called conservation or saving of energy.
One example of conservation of energy is given below.

To conserve
means to save or
not to waste.

What I have learnt

I must save energy at home and at school.
Through some of our bad habits we waste energy.
When we waste energy, we waste money.
We need to take all possible steps to avoid wastage of energy.

109

Unit 7 - Transformation of Energy

Teacher’s note pg 112-116

Answers to end of unit exercises

Exercise 1

1. D Chemical

2. C Heat

3. C A moving car

4. B Chemical to movement

5. C Transformation of energy

6. B Electrical to light

Exercise 2

(i) light heat
(ii) chemical
(iii) movement
(iv) chemical
(v) chemical
(vi) sound

Exercise 3

Devices that use electrical energy:
• Rice cooker
• Torch
• Computer

Exercise 4

a. Heat
b. Electrical
c. Chemical to Movement

Exercise 5

Statement √
1 Washing small amount of clothes in washing machines.
2 Leaving our TV set on when nobody is watching. √
3 Switching off all lights when nobody is present in a room. √
4 Leaving the refrigerator door open for long time.
5 Keeping only cold food in a refrigerator.
6 Leaving appliances on ‘sleep’ mode for long time.

110

Unit 7 - Transformation of Energy

Teacher’s note pg 112-116

Exercise 6
a. Electrical
b. Light and Sound
c. Wastage
d. Two lamps are on unnecessarily
e. Switch off all lights and the TV when nobody is in the room
Exercise 7
Electric lamps > electrical to light
Radio using cells > chemical to sound
Street lamp > light to electrical (day time)
Oil lamp > chemical to light
Exercise 8
The diagram should relate to two examples where energy is being saved though appropriate
measures taken. They can be use of energy-efficient bulbs or walking short distances.
After the diagram, pupils are also required to write a few lines on what ideas they are showing in
their diagrams.

111

Unit 7 - Transformation of Energy

End of Unit Exercises

Exercise 1

For each item, there is ONE correct answer. Circle the correct answer.
1. A cell can be used to light a bulb. Which type of energy is stored in the cell?
A heat B light C movement D chemical

2. When electrical energy is used to light a bulb, light energy is given out. Which other
form of energy is produced?
A sound B movement C heat D chemical
3. In which one of the following is chemical energy changed to movement energy ?
A a gas stove B an electric fan C a moving car D a TV set
4. What energy transformation takes place when a horse runs from one place to another?
A chemical to light B chemical to movement
C movement to chemical D electric to sound
5. Electrical energy from a battery becomes movement energy in a fan. This is an example of
A saving of energy
B wasting of energy
C transformation of energy
D production of energy
6. Energy is transformed from ................................. in a bulb.
A electrical to movement B electrical to light
C light to electrical D light to movement

112

Unit 7 - Transformation of Energy

Exercise 2

Complete the sentences using an appropriate word from the list below.You can use a

word more than once.

movement light chemical sound heat

(i) The energy transformation in an electric bulb is from electrical energy to heat

energy and ________________________ energy.

(ii) An animal uses ________________________ energy from food to move around.

(iii) In an electric fan electrical energy is converted into ________________ energy.

(iv) When cooking with wood, ________________energy is converted into_________ energy.

(v) The form of energy that is NOT obtained in a TV set is ________________________ energy.
(vi) A singing bird produces __________________ energy.

Exercise 3

Which of the following items make use of electrical energy? Tick (√) the correct answer.
(i) Rice cooker
(ii) Gas stove
(iii) Torch
(iv) Umbrella
(v) Computer

Exercise 4

The picture on the right shows bread being baked.

Fill in the blanks with correct words.

a. ____________ energy is needed to bake bread.

b. In the oven, _____________ energy is transformed to heat energy.

c. We eat the bread to get _____________to do our work or play.

d. The _______________ energy from the bread is changed to ________________ energy

that we use while walking or running around.

113

Unit 7 - Transformation of Energy

Exercise 5

In the table below, several statements are given. Tick (√) the statements that are
appropriate measures taken to save energy.

Statement √
1 Washing small amount of clothes in washing machines.
2 Leaving our TV set on when nobody is watching.
3 Switching off all lights when nobody is present in a room.
4 Leaving the refrigerator door open for long time.
5 Keeping only cold food in a refrigerator.
6 Leaving appliances on ‘sleep’ mode for long time.

Exercise 6

Study the picture below and answer the questions
that follow.The picture shows a TV playing in a room.

a. Name the form of energy that is being used by the television. ____________________
b. What two forms of energy are being produced by the television.
__________________________________________________________________________
c. Nobody is watching the television in the living room.It is an example of ____________ of energy.
d. Mention another way energy is being wasted in this room.
__________________________________________________________________________
e. State one way in which energy could be saved in the above example.
__________________________________________________________________________

114

Unit 7 - Transformation of Energy

Exercise 7

Draw a line to match each picture in colmun A to the transformation of energy in column B.

Column A Column B

Electrical lamps light to electrical (day)

A radio using cells chemical to light
A street lamp chemical to sound
An oil lamp electrical to light

115

Unit 7 - Transformation of Energy

Exercise 8

Draw, label and colour a diagram to show TWO ways in which you can save energy at
home and school.
You may write simple sentences to explain your drawing.

116

Unit 7 - Transformation of Energy

I check my progress

At the end of this unit, I can

• explain the energy transformations in various situations.
• give examples where energy is being wasted.
• state ways to save energy at home and at school.
• explain what is an energy efficient bulb.
• state the need for energy conservation.

117

Unit 7 - Transformation of Energy

Teacher’s note pg 119

Unit 8: The simple electric circuit
At the end of this unit your pupils should be able to:
• identify and name the different components of an electric circuit (cell, bulb, wire, switch).
• demonstrate that electrical energy flows in a complete circuit.
• investigate how a switch can be used to open and close a circuit.
• identify and compare conductors and insulators.
• infer that insulators help to prevent electric shocks.
• use an electric circuit to show the transformation of electrical energy into light, movement and

sound.
This unit is based entirely on experimentation. In order to carry out these activities in an efficient
manner, teacher must ensure that the following materials are available:
• A few electrical cells of different sizes and shapes.
• A few 1.5V electrical bulbs, a small electric fan, a small electric bell. (Or any other apparatus can
be used provided they produce movement and sound energy.)
• Some pieces of soft electrical wires of length 20-30cm.
• A simple switch.
• A pair of crocodile clips.

118

Unit 8 - The Simple Electric Circuit

The Simple Electric Circuit UNIT 8

In Units 6 and 7, you learnt that
all of us need energy to perform
our daily activities. You also learnt
about some sources and forms of
energy. For example, the sun and
the wind are sources of energy.
Light and heat are forms of energy.

We saw that one form of energy
can be transformed into other
forms. For example, electrical
energy can be transformed into
light, sound and heat energy.

In this unit, you will set up a simple electric circuit. You will learn about closed and open circuits
and the use of a switch. You will then study energy transformation in a circuit. You will classify
objects as conductors and insulators. You will also learn about some safety measures while
using electrical appliances.

At the end of this unit, you should be able to:

• identify and name the different components of a simple electric circuit.
• demonstrate that electricity flows in a complete circuit.
• investigate how a switch can be used to open and close an electric circuit.
• identify and compare conductors and insulators.
• infer that insulators prevent electric shocks.
• use an electric circuit to show the transformation of electrical energy into other forms.
• state precautions to be taken when using electrical appliances.

119

Unit 8 - The Simple Electric Circuit

Teacher’s note pg 121-123

Activity 8.1: Observing a cell, a bulb and a wire.

Aim: To introduce pupils to the different components of an electric circuit (Bulb, cell and electric
wire)

Learning outcomes:

• Identify the positive and negative ends of a cell.
• Infer through observations that all cells have these two connecting ends.
• Identify through observation the two connecting parts of a bulb.
• Deduce that electric wires are made of metal.

Skills: Observation, communication, social, inferring

Resources: cells, small bulbs, electrical wires.

Notes:
• Teacher asks pupils to work in groups and observe different types of cells, small bulbs and pieces
of electric wires.
• It is important for teacher to take into consideration safety aspects so that pupils do not break
the bulbs and cells. Pupils must not handle these alone but only in presence of teacher to avoid
injury with these and the electric wire.
• Teacher guides pupils to identify the positive and the negative signs on the cell.
• Through discussion, teacher helps pupils to infer that all cells have a positive and a negative end.
• Teacher then guides pupils to identify the two connecting parts of the bulbs.
• Teacher can then ask questions about what the electric wire is made up of. Teacher highlights
that the electric wire is made of metal.

For the last part of the activity, teacher can bring a picture of a car battery and ask pupils questions
such as “What does the picture show?”, “Where have you seen this object?”, “What is it used for?”
If the opportunity arises, show them a real car battery.

A battery stores energy. The car battery provides electrical energy to start the engine and to light
up the lamps and to produce sounds such as hooting or musical sounds.

The Find Out exercise encourages pupils to do some research work. They can be encouraged to
read at home and to discuss with their parents or other adults at home to find out the use of these
objects in their daily life.

120

Unit 8 - The Simple Electric Circuit

9 10
8

7 Activity 8.1 Observing a cell, a bulb and a wire
6
5
4
3
2
1
0

In Units 6 and 7, you learnt that the cell is an energy source. The cell stores chemical energy.
For example, it can provide electrical energy to light a bulb in a torch.

In this activity, you will learn about the cell, bulb and electrical wire.

What I need

An electric cell, pieces of electrical wire and a small bulb.

What I do and observe

(A) THE CELL

+Observe the top part of the electric cell. Do you see a sign?

This is called the positive end.

Figure 8.1: A Cell

Observe the bottom part of the cell.

-Do you see a sign? This is called the negative end.

Cells may be of different sizes and shapes as shown in Figure 8.2.

Figure 8.2: Different types of cells 121

Unit 8 - The Simple Electric Circuit

Observe Figure 8.2 and say what the cells have in common.
__________________________________________________________________________

Figure 8.3 shows a car battery.

Does it have a positive part and a negative part?_____________

What is the use of the car battery? Figure 8.3: A car battery
________________________________________________________

(B) THE BULB

Now observe the small bulb in Figure 8.4. It has two connecting parts. Figure 8.4 will help you
identify them as Part A and Part B.

Part A variety of small bulbs
Part B

Figure 8.4: A bulb

There exists a variety of small bulbs. They are of various shapes. All of them have two connecting
parts.
What do we use a bulb for?
_________________________________________________________________________

(C) THE WIRE
Observe the electrical wire. It has two connecting ends.
It is used to connect the cell to the bulb in an electric circuit.

end 1

end 2
122

Unit 8 - The Simple Electric Circuit

Let us observe an electrical wire more closely.

S What is this Part S made of?
T ______________________________________
What is this Part T made of?
______________________________________

You will learn later why an electrical wire is made up of a metal part and a plastic or rubber part.
It is the metal part that must be connected to different components of a circuit.

Did you know?

Most electrical wires are made of a metal called copper.

What I have learnt

All cells have a positive (+) and a negative (-) end.
A battery consists of many cells.
The positive and negative ends are always shown on cells and batteries.
A bulb has two connecting ends.
There is a variety of small bulbs.
An electrical wire has two parts. One part is made up of metal and the other of plastic or
rubber.
Electrical wires are used to connect different components in a circuit (for example, a bulb to
a cell).

9 10
8

7 Activity 8.2 Setting up a simple electric circuit
6
5 Question
4
3When does a bulb light up in a circuit? Let us find out by setting up a simple circuit.
2
1
0

123

Unit 8 - The Simple Electric Circuit

Teacher’s note pg 123-127

Activity 8.2: A simple electric circuit
Aim: To introduce pupils to a simple electric circuit.
Learning outcomes:
• To set up a simple electric circuit.
• To identify the different components of an electric circuit.
Skills: Observation, communication, social, inferring, psychomotor
Resources: A cell, two pieces of wire (about 30 cm long) and a small bulb
Notes:
• This activity is carried out in groups under the supervision of the teacher.
• Pupils follow the instructions given in their books to connect one end of the wire to the positive
end of the cell and the other end to the bulb.
• One end of the wire to the cell is connected to one end to the bulb. Teacher is advised to allow
pupils to guess whether the bulb will light up when the other end of the wire is connected to the
bulb. Pupils are encouraged to discuss and find out whether their guess was correct or not after
the connection has been made.
• Under teacher supervision, pupils then use the other piece of wire to complete the circuit as
suggested in the book and observe what happens.
• Teacher then introduces and explains the concept of “closed circuit” (complete circuit) and
“open circuit”. Teacher explains that in a closed circuit, electricity flows along the wire causing the
bulb to light. Teacher also highlights that electricity flows from the negative end of the cell to the
positive end.
• In an open circuit, electrical energy cannot flow so that the bulb does not light.
The Find out Section on the top of the page 127 in pupil's book will allow pupils to experiment
further with their teacher or adults at home and to discover that when 2 cells are used, the bulb
lights brighter. This is because there is more energy in 2 cells compared to one cell.

124

Unit 8 - The Simple Electric Circuit

What you need

A cell, two pieces of wire each about 30 cm long, a small bulb.

What you do

1. Work in small groups. Take one piece of wire. Call it wire 1.
2. Connect one end to the positive part of the cell.
3. Connect the other end to part A of the bulb as shown in Figure 8.5. Turn the metal part of
the wire around Part A of the bulb.

wire 1

Part B of bulb
Cell

Part A of bulb
Figure 8.5: Setting up a circuit

Observe the bulb. Does it light up? __________
Discuss with your friends and record your answer.
_______________________________________________________________________

4. Now take the other piece of wire. Call it wire 2. Connect one end to the negative part of the
cell.
You can hold the wires on the cell using an elastic band.
5. Connect the other end of wire 2 to part B of the bulb as shown in Figure 8.6.

wire 1

Part B of bulb

Cell

wire 2 Part A of bulb

Figure 8.6: A complete circuit

125

Unit 8 - The Simple Electric Circuit

Observe the bulb now.
Does it light up this time? _______________

Discuss with your friends and record your answer.
____________________________________________________________________

Complete the diagram below to show the transformation of energy.

___________ energy in the cell _________ energy in the wires _________ in
the bulb

State the form of energy that flows along the wires.__________________________

I remember Electrical ecnloesaTregnhdydinicstkihraciunfiokt.rm of energy that flows along electrical
wires in a

Explain the importance of the cell in the circuit.
_____________________________________________________________

In this experiment, we observe that the bulb gives off light.
This is because electricity is flowing along the circuit.
We call this a closed circuit.
A closed circuit is also called a complete circuit.
Electricity is a form of energy that only flows in a closed circuit.

Now let us go back to Figure 8.5.
Does electricity flow along wire 1? _________________
Is the circuit closed? ________________________

I conclude from my observations

In an open circuit, electricity does not flow. So the bulb does not light up.
In a closed circuit, electricity flows. So the bulb lights up.

Discuss about the importance of the wire in the circuit.

126

Unit 8 - The Simple Electric Circuit

Find What happens if we use two cells instead of one in a circuit?
out

Arrange two cells as shown in the picture. Connect them to the circuit in Figure 8.6.

Compare the light given off when there is (i) one cell and (ii) two cells.

What do you observe?

________________________________________________________________________

Can you say why? Think of what a cell stores.

__________________________________________________________________________

What I have learnt

A simple electric circuit consists of a bulb and a cell connected by electrical wires.
In an open circuit, electricity does not flow. A bulb will not light up.
In a closed circuit, electricity flows. A bulb will light up.
A bulb must be connected properly in a circuit to light up.
Electricity is a form of energy that flows in a closed circuit.
A cell produces electricity when connected in a complete circuit.

Find Find out the use of cells, bulbs and wires in everyday life.
out

Keywords to learn 127

circuit connect cell battery open closed bulb electricity

Unit 8 - The Simple Electric Circuit

Teacher’s note pg 129-131

Activity 8.3: Adding a switch to an electric circuit

Aim: To develop an understanding of the importance of a switch in an electric circuit.

Learning outcomes:
• To identify a switch in the classroom.
• To infer the importance of a switch in an electric circuit.

Skills: Observation, literacy, writing, psychomotor, communication, social

Resources: A cell, three pieces of wire each about 30 cm long, a small bulb and a switch.

Notes:
• After observing the picture of the switch given in the book, teacher discusses with pupils to
guide them to identify a switch in their classroom.
• Teacher must ensure that pupils just identify the switch, but do not play with the switch for safety
considerations.
• Under teacher supervision, pupils will set up an electric circuit that would include a switch as
shown in Figure 8.9.
• Through this activity, bring pupils to find out that when the switch is on, it allows the circuit to be
closed (complete) and the bulb lights. But when the switch is off, it causes the circuit to be open
and the bulb does not light.
• The following can be used by teacher to help pupils understand the importance of switches:

Switch is off circuit is open no flow of electricity no light

Switch is on circuit is closed or complete flow of electricity light

• To end this activity, teacher can discuss about the importance of switches at home.
• It is important for teacher to advise pupils that they should not play with switches at school or

at home.

128

Unit 8 - The Simple Electric Circuit

9 10
8

7 Activity 8.3 Adding a switch to an electric circuit
6
5
4
3
2
1
0

Figure 8.7 shows the picture of a switch. A gap
part 2
Note that the switch has two connecting parts. part 1
Figure 8.7: A switch
There is a variety of switches.

The switch shown in Figure 8.7 is called a tap switch.

To switch it on, you press (tap) on it at connecting

part 2.

Is there a switch in your classroom?_________________

Why do we use a switch? We use a switch either to open or to close a circuit.

Question

How do we add a switch to the electric circuit? Let us find out.

What you need

3 pieces of wire, a cell, a small bulb and a switch.

What you do

ST

Figure 8.8: A open circuit
Set up an electric circuit as shown in Figure 8.8.
Is the circuit closed or open? __________
How do you know?___________________________________________________________

129

Unit 8 - The Simple Electric Circuit
Explain what will happen if you join wire S to wire T?
__________________________________________________________________________

ST

Figure 8.9: Connecting a switch to a circuit
Now hold the switch. Identify its two connecting parts.
Connect one part to wire S.
Connect the other part to wire T as shown in Figure 8.9.

Questions

Observe the bulb. Is the circuit closed or open?_________________
How do you know?
_____________________________________________________________________
Is the switch on or off? ____________________
Now press the switch down at T. Observe the bulb. What happens this time?
_____________________________________________________________________
Is the switch on or off? ______________________
What can you say about the circuit? ________________________________________
Can you now explain the use of a switch?
_______________________________________________________________________
130

Unit 8 - The Simple Electric Circuit
Explain why the light or fan is on when you press the switch in your classroom.
Think of a complete circuit and why we use a switch.
______________________________________________________________________

I conclude from my observations

Electrical energy always flows in a closed or complete circuit.
A switch is an important part of a circuit.
We use a switch to either close or open an electric circuit.

What I have learnt

A switch closes or opens a circuit.

Discuss with your friends using the terms
switch off - open circuit - no light
switch on - closed circuit – light

131

Unit 8 - The Simple Electric Circuit

Teacher’s note pg 134-139

Activities 8.4 - 8.6

Aim: To demonstrate that energy transformation occurs in an electric circuit.

Learning outcomes:
• To recall that electrical energy can be transformed into other forms of energy.
• To identify the cell as a source of chemical energy.
• To infer that energy transformation occurs in an electric circuit.
• To deduce that chemical energy in the cell can be transformed into light energy and heat
energy (using a bulb), movement energy (using a motor or fan) or sound energy (using a bell)

Skills: Observation, social, psychomotor, literacy, writing, inferring

Resources:
A complete electric circuit including the wires, cell, bulb and switch.
A small electric motor or fan, a small electric alarm or bell (teacher must ensure that these devices
are able to operate with the current produced by the cell). Teacher can also ask pupils to bring
from home simple battery-operated toys that involve the transformation of electrical energy into
sound energy and/or light energy and/or movement energy.

Notes:
• Teacher starts with Activity 8.4 by a brainstorming session on energy transformation. For example
teacher can ask pupils what energy transformation occurs in the following devices when they are
being used:
(i) an electric lamp (ii) electric iron (iii) torch.
• Pupils work in pairs to complete the table on page 134 in pupil's book.
• Through discussion, teacher can help pupils to recall what they have learnt in Unit 7 on Energy
transformation.

Activity 8.5

• Under close teacher supervision, pupils will carry out Activity 8.5 in groups. It is very important
for the teacher to closely monitor pupils. Pupils should not play with the bulb or break the bulb to
avoid injury.
• It is important for each group to correctly connect the bulb to the circuit. They should also be
given time to observe, discuss and write down their observations.
• After pupils have completed the activity, whole-class discussion follows and teacher highlights that:
chemical energy in the cell is transformed into light energy and heat energy in the bulb.

132

Unit 8 - The Simple Electric Circuit

Teacher’s note pg 134-139

Activity 8.6
• Teacher will carry out Activity 8.6 for the pupils.
• Pupils will be required to observe carefully as the teacher replaces the bulb by the small electric
motor or fan and by an electric alarm or bell.
• Pupils will discuss in pairs and complete the given table to show the transformation of energy
occurring in each case.
• Motor or fan
chemical energy (in the cell) is transformed into electrical energy (in the wire) and then into
movement energy.
• Bell or alarm,
chemical energy (in the cell) is transformed into electrical energy (in the wire) and then into
movement energy and sound energy.
• Teacher can extend the activity using other simple devices or toys brought by himself/herself
or by pupils.
• In the Find out section on page 139 in pupil's book, teacher encourages pupils to discuss with
their parents or other adults at home to identify other electrical appliances used at home (eg.
Toaster, electric oven, washing machine etc.) and to find out the energy transformations which
occur in the electric devices they have identified. Teacher can also ask pupils to work in groups
and to report their findings in the form of a poster which can be presented by each group.

133

Unit 8 - The Simple Electric Circuit

9 10
8

7
6
5
4
3
2
1
0
Activity 8.4 Transformation of electrical energy

In Unit 7, you learnt that electrical energy can be transformed into other forms of energy.
For example, electrical energy can be transformed into light energy in a lamp.
Write the energy transformation for an electric lamp.

an electric lamp

Give TWO more examples of simple devices where electrical energy is transformed into
other forms of energy.
Draw and name the device in column A and write the energy transformation in Column B.

Column A Column B

134

Unit 8 - The Simple Electric Circuit

9 10
8

7 Activity 8.5 Transformation of electrical energy into light
6
5
4
3
2
1
0

and heat energy in a circuit

We are now going to use our circuit to observe the transformation of electrical energy into
light and heat energy.

Question

What is the energy transformation in a simple circuit? Let us find out.

What you need

a bulb an electrical wire an elastic band a cell

What you do

Connect the wire to the bulb.
Turn the metal part of the wire around the
bulb as shown.

Now connect the bulb and wire to the cell as
shown.

135

Unit 8 - The Simple Electric Circuit

What you observe

Observe the bulb. What happens?
____________________________________________________________________
Touch it. What do you feel? Is the bulb warm or cold? (Be careful when touching the bulb)
________________________________________________________________________

Questions

Which forms of energy are obtained?
1. ________________________________ 2. __________________________________

What energy transformations can we conclude from this activity? Draw a diagram to show it.
________________________________________________________________________

I conclude from my observations

Chemical energy that is stored in the cell is turned into light energy and heat energy.

Light energy in the bulb

Heat energy in the bulb
Chemical energy in the cell

136

9 10 Unit 8 - The Simple Electric Circuit
8
Activity 8.6 Transformation of electrical energy to
7 movement energy in a circuit
6
5We are now going to use our circuit to observe the transformation of electrical energy to
4movement energy.
3We can often find a small electric motor in a broken toy that needs a battery to work.
2Can you find one and bring it to your class?
1
0

What you need an electric motor

a small electric motor, a small electric fan, a small electric bell or buzzer.

What you do

Use the circuit of Figure 8.9. S T
Lay the circuit on the table.
Identify the two connecting parts of the motor.
Replace the bulb by the motor in the circuit.
Switch ON the circuit.

What do you observe?
________________________________________________

Now fill the table below to show the transformation of energy in the circuit.

In the cell In the wire In the motor

Chemical energy

137

Unit 8 - The Simple Electric Circuit

Now fill the table below to show the transformation of energy in the circuit if the bulb
is replaced by:

(A) the fan
(B) the bell/buzzer

In the cell In the wire In the fan

Chemical energy

In the cell In the wire In the bell/buzzer
Chemical energy

I conclude from my observations

A simple circuit can be used to show the transformation of energy.

Chemical Energy Electrical Energy Light Energy
Heat Energy
Sound energy

138

Unit 8 - The Simple Electric Circuit

What I have learnt

A simple circuit can be used to show transformation of energy.

Find At home we use different types of electrical appliances.
out Find out and name two of them.

State the energy transformation in each of the electrical appliances when they are switched on.
1. ______________________________________________________________________
2.______________________________________________________________________

139

Unit 8 - The Simple Electric Circuit

Teacher’s note pg 141-145

Activity 8.7: Classifying objects as conductors and non-conductors (insulators) of electricity.

Aim: To introduce pupils to conductors and non-conductors of electricity.

Learning outcomes:
• To distinguish between conductors and non-conductors of electricity
• To identify metals as conductors of electricity.
• To infer that plastic, glass, paper and rubber are non-conductors of electricity
• To give examples of other non-conductors of electricity
• To develop an understanding of the importance of non-conductors of electricity in preventing
electric shock.

Skills: Observation, comparing, classifying, inferring, literacy, social, writing.

Resources:
A complete circuit, piece of thread, a dry lollipop stick, a coin, a piece of glass (Ensure safety
aspect), a rubber band, a clean iron nail, a plastic ruler, a metal ruler, other pieces of metals if
available.

• It is important for teacher to ensure safety aspects when working with all these materials.
• The activity must be carried out under close supervision of teacher. Pupils should not be allowed
to carry out the activity on their own.
• After inserting each object in the gap in the circuit, teacher can encourage pupils to predict
what will happen when the switch is put on. Then the switch is put on and pupils observe carefully
to see what happens and to check whether their prediction was right or not. Teacher also gives
time to pupils to discuss and note down their observation. The same procedure is repeated by
replacing other materials, one at a time in the gap. (Teacher can also seize this opportunity to
revisit and consolidate the concept of open/closed circuit.)
• After completing the experiment, teacher asks pupils to classify the different materials into groups
- those that conduct electricity and those that do not. Through discussion, teacher explains the
term conductors and non-conductors or insulators.

• In the next part of the activity, teacher can bring electric wires wrapped in their plastic coating
and ask pupils the importance of the plastic coating. Bring pupils to realize the importance of
plastic as an insulator – it helps to protect us from electric shocks.

Safe use of electricity on page 144-145 in pupil's book

The last part of this chapter is important to highlight the safety precautions to observe when using
electrical appliances. Teacher can also use pictures to demonstrate these safety measures.

140