Green house Effect
Activity 14.1
List
four forms of energy that you use from morning, when you
wake up, till you reach the school.
From
where do we get these different forms of energy?
Can
we call these ‘sources’ of energy? Why or why not?
walk by the foot using muscular energy. The food we prepare uses
the chemical energy of the liquified petroleum gas (LPG). During our day to day
activity, we use electrical energy to run our fans, geysers, air conditioners,
etc. Some of our gadgets like calculator, solar lamp, toys run use the energy
of sunlight to charge the batteries.
Muscular energy in our body comes from the chemical
breakdown of carbohydrates and glucose from the cells. LPG comes in the
cylinder from a gas supplier which they procure during extraction of fossil
fuels. We get electrical energy from various sources. A thermal power plant uses
coal to produce electricity; a hydroelectric power plant uses the potential
energy of water. Similarly, a solar plant uses the energy of sunlight, etc. We
obtain solar energy by using solar panels attached to the appliances which
store solar energy in batteries.
These form of energy like heat energy, electrical
energy, muscular energy, an energy of a battery/cell are not the ultimate
source of energy. They are an indirect form of energy obtained by conversion
from another energy form.
Source of energy needs to be abundant in nature and
freely available, eg. Solar energy, wind energy, hydro energy, fossil energy,
etc.
Activity 14.2
Consider
the various options we have when we choose a fuel for
cooking our food.
What
are the criteria you would consider when trying to categorise
something as a good fuel?
Would
your choice be different if you lived
(a) in a forest?
(b) in a remote mountain village or small island?
(c) in New Delhi?
(d) lived five centuries ago?
How
are the factors different in each case?
Electricity, LPG, Wood, Coal, solar cooker, etc. prefer LPG
and electricity as they are highly efficient, does not cause smoke, and are
easy to use.
Good fuel is a fuel which is easily available, cheap, clean, and
easy to use.
Categorizing fuels
State of fuel: Solid, liquid, gas. Ease of use: Easy to handle,
hard to handle. Here electricity and LPG are easy to handle while using wood is
cumbersome. Economy: Cheap vs costly fuels. eg. Coal vs petrol. Pollution:
Clean fuel vs polluting fuel. Electricity, solar cooker, LPG are clean fuels,
as they do not produce smoke while wood and coal fall in the second category.
Choice of Fuel: a. in forest wood or solar cooker if available
b.Solar cooker
c. LPG & Electric
d. wood, coal, cow dung
Questions
1. What is a good source of energy?
Answer:
A good source of energy has the following properties:
·
Be economical
·
Easy storage and transportation
·
Easy availability
·
Work done per unit volume or mass should be large.
2. What is a good fuel?
Answer:
A fuel is said to be good when it is easily available and when it
produces a large amount of heat energy when burnt.
3. If you could use any source of energy for heating your food,
which one would you use and why?
Answer:
For heating and cooking, natural gas can be used for the below
given reasons:
·
It is easy for using
·
It is easily available
·
Easy transportation
·
It does not produce huge amount of smoke when burnt
·
It is highly inflammable.
Thermal Power Plant Working
Wind Mill Pump
1. What are the disadvantages of fossil fuels?
Answer:
Following are the disadvantages of fossil fuels:
·
Fossil fuels like coal and petroleum results in air pollution as
there is release of huge amount of pollutants.
·
Gases such as carbon dioxide is released when a fossil fuel is
burnt which causes global warming.
·
Soil fertility and potable water is affected by the oxides of
carbon, nitrogen, sulphur, etc. that are released from fossil fuels.
2. Why are we looking at alternate sources of energy?
Answer:
The reason why we are looking at alternate sources of energy is
because the fossil fuels are non-renewable source of energy i.e. they are not
available in large quantities and it cannot be replenished. Fossil fuels will
get exhausted if their consumption is not controlled. Therefore, it is better
to switch to alternate source of energy.
3. How has the traditional use of wind and water energy been
modified for our convenience?
Answer:
In olden days, wind energy was trapped used windmills to do
mechanical works like lifting or drawing water from a well. But these days,
windmills are used to generate electricity. The kinetic energy of wind is
trapped and converted into electricity with the help of rotatory motion of the
blades which turns the turbine of the electric generator to produce
electricity.
Similarly, waterfalls were the source of potential energy in
olden days. But these days as the number of waterfalls as reduced, water dams
are constructed and are used as a source to trap the potential energy. Here, the
water falls from a certain height on the turbine producing electricity.
Activity 14.6
Solar Cooker
Solar Water Heater
Working
Tidal Energy
Various ways to generate electricity from ocean
How Solar Panels are made
14.3 ALTERNATE OR NON-CONVENTIONAL SOURCE OF ENERGY
1. What kind of mirror – concave, convex or plain would be best
suited for use in a solar cooker? Why?
Answer:
For a solar cooker the heat source is sunlight for heating and
cooking. The reason why a mirror is used is to reflect and focus the sunlight
at one point. So a concave mirror can be used in a solar cooker, as it focuses
all the sunlight at one point resulting in increase in temperature, thereby
heating and cooking the food.
2. What are the limitations of the energy that can be obtained
from the ocean?
Answer:
The different forms of energy that can be obtained from the
ocean are tidal energy, wave energy and ocean thermal energy. Following are the
limitations of the energy obtained from ocean:
The relative positioning of the earth, the sun and the moon as
an impact on the tidal energy.
For the conversion of tidal energy into electricity, high dams
are required.
To obtain electricity from wave energy, very strong waves are
required.
For trapping the ocean thermal energy, there should be a
temperature difference of more than 20°C
between hot surface water and the cold water at a depth.
3. What is geothermal energy?
Answer:
Geothermal energy cab be defined as the energy that is obtained from
the earth. The energy can be obtained from the hot spots that are formed when
the molten rocks at the core of the earth are pushed to the earth’s crust.
Hot springs are used for the production of electricity in the
geothermal power plants.
4. What are the advantages of nuclear energy?
Answer:
Following are the advantages of nuclear energy:
Amount of energy produced per unit mass is large
As it does not produce any pollutants, it is clean
Fission of 1 atom of uranium produces 10 million times the energy
that is obtained by burning 1 atom 
of
carbon
14.4. ENVIRONMENTAL CONSEQUENCES
1. Can any source of energy be pollution-free? Why or why not?
Answer:
No source of energy can be pollution-free. But solar cells are
considered to be pollution-free. But their manufacturing may cause
environmental damage. In case of nuclear energy, the waste produced after
fusion is zero. But the wastes that are produced during fission are hazardous.
Hence, no source of energy is pollution free.
2. Hydrogen has been used as a rocket fuel. Would you consider it
a cleaner fuel than CNG? Why or why
not?
Answer:
Hydrogen gas is cleaner than CNG as CNG contains hydrocarbons.
Carbon is a form of pollutant in CNG.
On the other hand, hydrogen is waste-free and the fusion of
hydrogen does not produce any waste. Hence, hydrogen as a rocket fuel is
cleaner than the CNG.
Questions
1. Name two energy sources that you would consider to be
renewable. Give reasons for your choices.
Answer:
Following are the two sources of energy that are renewable:
(i) Wind: Wind energy is obtained from the air which is blowing at
a high speed. Wind energy is trapped using windmills so as to generate
electricity. Blowing of air is dependent on uneven heating of the earth.
Since the heating of the earth is forever, wind availability will
also be forever.
(ii) Sun: The energy obtained from the sun is known as solar
energy. It is produced by the fusion of hydrogen into helium, fusion of helium
into other heavy metals and it continues. A large amount of hydrogen and helium
is available in sun which will never be exhausted. Hence solar energy is
renewable source of energy.
2. Give the names of two energy sources that you would consider to
be exhaustible. Give reasons for your choices.
Answer:
Following are the two sources of energy that are exhaustible:
(i) Wood: The source of wood are forests. Due to deforestation the
number of forests are reducing. We know that it takes years to grow forest. If
the rate of deforestation increases, the availability of wood will decrease.
Hence, wood is an exhaustible source of energy.
(ii) Coal: The source of coal is from the dead remains of the
plants and animals that remained buried for years. Industrialization has
increased the demand for coal and it cannot be replenished. Hence, coal is also
an exhaustible source of energy.
Exercises
1. A solar water heater cannot be used to get hot water on
a) A sunny day
b) A cloudy day
c) A hot day
d) A windy day
Answer:
b) A sunny day A solar water heater uses solar energy to heat
water. On a cloudy day, the sunlight won’t be intense and bright enough and it
gets reflected back in the sky from the clouds. This holds the sunlight from
reaching the ground. Therefore, solar energy won’t available for the solar
water heater to heat the water.
2. Which of the following is not an example of a bio-mass energy
source?
a) Wood
b) Gobar-gas
c) Nuclear energy
d) Coal
Answer:
c) Nuclear energy
Bio-mass is obtained from the dead plants and animal wastes. In
these dead plants and animals there is a chemical change as they react with
water and sunlight. But nuclear energy is obtained by fusion and fission of
atoms resulting in tremendous release of energy. Both nuclear fusion and
fission can be carried out in the absence of the sunlight.
Wood is a part of plant, gobar-gas is obtained from the animal
dung and coal is obtained by the dead remains of the plants and animals.
Therefore, they are all bio-mass energy products.
3. Most of the sources of energy we use represent stored solar
energy. Which of the following is not ultimately derived from the sun’s energy?
a) Geothermal energy
b) Wind energy
c) Nuclear energy
d) Bio-mass
Answer:
c) Nuclear energy
Nuclear energy is produced by nuclear fusion and nuclear fission.
In nuclear fission, uranium atoms are bombarded with low energy neutrons
resulting in splitting of the atom into two relatively lighter nuclei. In nuclear
fusion, lighter nuclei are fused together to form a relatively heavier nuclei.
The energy produced
in nuclear reaction is tremendous and can be carried out in the
absence of sunlight.
Geothermal energy is obtained from the deep stored energy in the
form heat in the earth’s crust. The uneven heating of the earth’s surface
results in wind movement and bio-mass is obtained from the dead remains of the
plants and the animals.
4. Compare and contrast fossil fuels and the sun as direct sources
of energy.
Answer:
Fossil fuels are obtained from the earth’s crust as they are the
remains of the dead plants and animals. They are similar to coal and petroleum
and readily available for the use. These are non-renewable source of energy and
cannot be replenished.
Whereas solar energy is abundant in nature and can be replenished.
5. Compare and contrast bio-mass and hydroelectricity as sources
of energy.
Answer:
Bio-mass is obtained from the dead plants and animals. It
renewable source of energy. Examples of biomass sources of energies are wood,
gobar-gas.
Hydroelectricity is obtained from the potential energy of the
stored water at a certain height. Water from a certain height is made to fall
on the turbines of the generator resulting in electricity. Dams and reservoirs are
used in hydroelectricity.
Both bio-mass and hydroelectricity are renewable sources of
energies.
6. What are the limitations of extracting energy from:
a) The wind?
b) Waves?
c) Tides?
Answer:
a) The wind: Wind energy is trapped using windmills. One of the
limitations of the wind energy is that the windmills requires a speed more than
15 km/h to generate electricity. And the number of windmills will be more to
cover a huge area.
b) Waves: In order to extract energy from the waves, very strong
ocean waves are needed.
c) Tides: In order to extract energy from the tides, the sun, the
moon and the earth should be in a straight alignment and the tides should be
very strong.
7. On what basis would you classify energy sources as:
a) Renewable and non-renewable?
b) Exhaustible and inexhaustible?
Are the options given in (a) and (b) the same?
Answer:
(a) Renewable and non-renewable:
Renewable energy sources are those which replenish on their own
and are easily available in nature. Like solar energy, tidal energy, wind
energy, bio-mass.
Non-renewable energy sources are those which do not replenish on
their own and have limited in availability in nature. Like fossil fuels which
includes petroleum, coal and natural gas.
(b) Exhaustible and inexhaustible:
Exhaustible source of energy are those which deplete after few
hundred years. Like coal and petroleum.
Inexhaustible source of energy are those which do not deplete and
are available in abundant quantity. Like solar and wind energy.
8. What are the qualities of an ideal source of energy?
Answer:
Following are the qualities of an ideal source of energy:
It should be economical
It should be easily available
Pollution free
Easy transportation and storage
The amount of energy produced when burnt should be huge.
9. What are the advantages and disadvantages of using a solar
cooker? Are there places where solar cookers would have limited utility?
Answer:
Advantages:
The heat source for a solar cooker is sunlight. It is a clean renewable
and inexhaustible source of energy. As its availability is unlimited, it will
be pocket-friendly.
Disadvantages:
It doesn’t work on a cloudy day.
10. What are the environmental consequences of the increasing
demand for energy? What steps would you suggest to reduce energy consumption?
Answer:
Industrialization demands for more energy and to fulfil these
demands fossil fuels are used as they are readily available. Due to their harsh
usage, it has an impact on the environment. Too much exploitation of fossil
fuels has led to greenhouse effect resulting in global warming.
But there are few possibilities of reducing this by reducing the
usage of fossil fuels and opting for alternate sources of energy. Reducing the
unnecessary usage of electricity and water. Opting for public transportation
and reducing using own vehicles. These are few small steps that can be
implemented for reducing the energy consumption
Comments
Post a Comment