04 Energy in Day-to-Day Life

S ome events of the Sinhala-Hindu New Year festival and a procession

are given in the following pictures.

Fig. 4.1 Events of the Sinhala-Hindu New year festival and a procession

Assignment 4.1
List the different games and special activities taking place in
these events.

Now, think about these activities. It is clear, that some work is done
in all these activities. Now, let's focus on some activities done in our
day-to-day life. Pulling a log using a rope, carrying a heavy load of soil
by a wheel barrow, loading of goods to a vehicle are some common
examples. We understand that energy is needed to do all these activities.
What is energy ? Energy is defined as the ability to do work.

Use of energy to do work

Let’s do Activity 4.1 to understand how energy can be utilized to do
work.
Science | Energy in day to day life 49
 Activity 4.1
Let’s make a wind propeller
You will need (- Oil papers with different colours, a thin wire, a
used ballpoint pen, a small piece of cardboard, a
pair of scissors

Fig. 4.2 Fig. 4.3

yy Cut 10 pieces of coloured oil papers into triangles as shown in

Fig. 4.2.
yy Make two holes in each piece as shown in Fig. 4.2.
yy Insert the wire into one hole of each paper and fix all pieces to
the wire.
yy After fixing the pieces insert rest of the holes into the wire to
make the wind propeller (Fig. 4.3).
yy Now, insert two small cardboard circles from top and bottom of
the wire.
yy Now, bend the top edge of the propeller.
yy Finally, fix the other end of the wire tightly to the barrel of the
ballpoint pen.
yy Now hold it to the blowing wind. See what happens.

The wind propeller rotates when there is wind. When the wind speed is
higher, the propeller rotates faster.
The rotation of the wind propeller indicates a task. How did the wind
propeller get the energy ? It was provided by the blowing wind.

50 Science | Energy in day to day life

Now let's focus on a "solar thermal stove / cooker"
shown in Fig. 4.4. What is a solar thermal cooker?
It can be used to cook food and boil water. Do you
know how does the cooker get energy ? To find the
answer let's do the following activity.

Fig. 4.4 Solar thermal stove / cooker

Activity 4.2
Demonstrate the function of a solar thermal box stove
You will need :- A piece of cardboard of the size 30x30 cm, a pair of
scissors, binder gum, a piece of aluminium foil of the size 30x30 cm,
two beakers of 50 ml, a thermometer, some pieces of paper, a sheet of
glass of the size 20x20 cm
Method :-
• Paste the aluminium foil one side of the cardboard with binder gum.
• Draw lines on the cardboard as shown in Fig 4.5 and cut off the
four shaded parts. 20 cm
cm
2020cm

20 cm
20 cm
10 cm 10 cm
20 20
cm
30 cm

10 cm

cm
30 cm

10 cm

20 cm
20 cm

30 cm 2 rEmh
Picture 01 Fig 4.5
30 cm rEmh 02
2 Picture
1 rEmh
• Fold the parts of the cardboard
1 rEmh and make a box as shown in Fig 4.5.
Paste the edges with paper stripes.(The aluminium foil should go
inside the box)
• Put 30 ml of water into each beaker and record the temperature of
water.
• Keep the box at a place with good sunlight and keep one beaker
inside the box and the other outside the box. Close the box with
the sheet of glass.
• Remove the sheet of glass and measure the temperature of water in
the two beakers after 15 minutes.
Science | Energy in day to day life 51
The beaker inside the cooker absorbs more solar energy than the beaker
kept outside due to the special arrangement of the cooker. Therefore,
the temperature of the beaker inside the box is higher than the beaker
kept outside the box. This happens due to solar energy.

Thermometers are used to measure the temperature. Temperature

is measured in Celcius or Fahrenheit. Temperature is measured in
Celcius (0C) in day-to-day applications.

When you cook using a solar thermal stove / cooker, solar energy is
used. Solar enenrgy is used in many day-to-day activities. For example,
drying of chillies / clothes, grains and for making “Lunu dehi”.
Activity 4.1 demonstrates the use of wind energy to rotate a wind
propeller. Activity 4.2 shows the use of solar energy to heat water and
cook food. There are a large number of enenrgy sources.
e.g : Sun, biomass, fossil fuel, wind, running water, sea waves, tidal
waves, geothermal and nuclear power
Table 4.1 summarises the examples of different activities that use
energy and the respective energy source.

Table 4.1- Examples of use of energy and respective energy source.

Activity Source of Energy
Drying of chillies Sun
Running a vehicle Petrol /diesel(fossil fuel)
Cooking a meal Fire-wood (biomass) / L.P. gas
Ironing clothes Coconut shell (biomass) / Electricity
Heating water Liquid petroleum (L.P gas) / Electricity/
biomass / fossil fuel
Now, let’s study about other sources of energy.

52 Science | Energy in day to day life

4.1 Energy Sources and Their Applications
Sun
Think of some of the activities you did
today. If you do not have sufficient energy,
can you do them ? How did you get the
energy? Energy needed for these activities
are supplied from food you eat.
Food for all living beings is produced in
green plants. Sunlight is needed for the Fig 4.6 Sun
process of producing food in green plants.
Therefore, energy in food is derived from solar energy.
Sun is the main natural energy source on the earth . It is essential for the
existence of life on earth. This energy can be utilized in many ways as
in drying grains and drying wet clothes.

Fig. 4.7 Solar water heater Fig. 4.8 Solar panel

Fig. 4.7 shows a solar water heater which is located on the roofs of
some houses. This can be used to heat water. Solar panels are used in
some occasions where electrcity cannot be obtained from the main
electricity supply to power some electric appliances. Solar panels obtain

Science | Energy in day to day life 53

their energy from sunlight. Even satellites obtain power from solar
panels containing many solar cells.

Assignment 4.2
Prepare a list of instances where solar energy is used.

Biomass
Living materials can produce energy. Think of a wild fire which occurs
commonly during drought seasons. Controlling of such fire is very
difficult because dried leaves catch fire easily. Such fires release large
amount of heat. This proves
that living parts can be used to
produce energy. Such plant or
animal materials which can be
used as a fuel, are known as
“biomass”.
Firewood is one of the commonly
used biomass. Other examples of
Fig. 4.9 Biomass (Firewood)
biomass are coconut shells, coal,
rotten vegetables, hay, saw dust, rice bran, rotten food materials and
agricultural waste. Biomass also contains solar energy.
Saw dust stove or "kudu lipa" / "thool aduppu" is one example, where
biomass is used. Here, rice bran or saw dust is used as biomass. Make a
saw dust stove with the help of your teacher .

Activity 4.3
Let's make a saw dust stove or “kudu lipa”/ "thool aduppu".
You will need (- A tin without a lid, long nail or alis bodkin, tin
cutter, PVC tube (4 cm diameter and 30cm long),
hacksaw blade, saw dust or rice brans

54 Science | Energy in day to day life

 Method (
yy Make a circular hole of 4cm
diameter close to the bottom edge
of the tin.
yy Insert the PVC tube from the
prepared hole into the tin as shown
in the figure. Push it to the centre
of the tin and cut it leaving 4 cm
outside the tin.
yy Then, put another PVC tube
vertically inside the tin and fill the
tin with saw dust or rice brans. Fig. 4.10
yy This should be packed thoroughly by using a piece of wood.
yy Now, remove the two PVC tubes carefully.
yy An “L” shaped hole is made inside the tin. Light the stove by
inserting a flame from the lower end.

This is a very simple economical hearth which can be used to cook

meals and to boil water.

Assignment 4.3
Let’s find examples where biomass is used to obtain energy.
Copy the table given below into your writing book. Complete it with
more examples.
Instances where it is used to obtain
Biomass
energy
Firewood
Coal
Hay
Sugar cane
Waste matter from the kitchen

Science | Energy in day to day life 55

 Fossil Fuel
Do you know how did the old train engines get energy? It was produced
by burning coal. The heat emitted during the burning of coal was used
to convert water to steam. The energy generated by steam was used to
operate engines. Coal, petroleum oil and petroleum gases are considered
as fossil fuel. These fossil fuels are
accumulated under different parts of
the inner earth. These fuels are made
from the buried plants and animals.
They are produced when this buried
matter is subjected to high pressure
and temperature. This process takes
millions of years. Solar energy is the
stored energy in the fossil fuel too.

Fig. 4.11 Petroleum oil well

Assignment 4.4

Some examples for the use of fossil fuels are given below. Name a
fuel / fuels used in each of these occasions.

1 2 3

4 5 6

56 Science | Energy in day to day life