NCERT Solutions for Class 10 Science Chapter 14 Source of Energy

NCERT Solutions for Class 10 Science Chapter 14 Source of Energy – Students will discuss about different type of sources of energy and they are conventional sources of energy, which we keep on using for many years. It includes fossil fuels, thermal power plants and hydropower plants and their advantages and disadvantages.

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Students who are preparing for their Class 10 exams and searching for chapter-wise NCERT Solution for Class 10 Science must go through NCERT Solutions for Class 10 Science Chapter 14 Source of Energy. Checkout previous chapter – NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current

Also Check – NCERT Solutions for Class 9 Maths

NCERT Solutions for Class 10 Science Chapter 14 In-text Questions

Page No.- 243

Question 1
What is a good source of energy?
Answer:
A good source of energy is one that

1. Easy storage and transportation
2. Be economical
3. Work done per unit volume or mass should be large.
4. Easy availability

Question 2
What is a good fuel ?
OR
Write any three characteristics of a good fuel. [AICBSE 2015]
Answer:
A good fuel is one which has the following properties :

1. It should be fairly cheap.
2. It should be easily available.
3. Its ignition temperature should be well above normal temperature.
4. It should be conveniently handled and transported.
5. It should not produce any poisonous material during burning.
6. Its combustion rate should be steady and controllable.
7. It should not leave any residue or ash after burning.
8. A good fuel should have high calorific value so that higher amount of heat may be obtained by burning a little fuel.

Question 3
If you could use any source of energy for heating your food, which one should you use and why ?
Answer:
I would prefer to use cooking gas like LPG. It fulfils many of the criteria of a good fuel like its ignition temperature, good calorific value and non-polluting characteristics.

Page No.- 248

Question 1
What are the disadvantages of fossil fuels ?
Answer:
(i) The burning of fossil fuels produces large amount of carbon dioxide that causes increased greenhouse effect.
(ii) Fossil fuels like coal and petroleum results in air pollution as there is release of huge amount of pollutants.

(iii) The burning of fossil fuels produces acidic gases such as sulphur dioxide and nitrogen oxide. These acidic gases cause acid rain that affects our water and soil resources.
(iv) Soil fertility and potable water is affected by the oxides of carbon, nitrogen, sulphur, etc. that are released from fossil fuels.

(v) Gases such as carbon dioxide is released when a fossil fuel is burnt, which causes global warming.

Question 2
Why are we looking at alternate sources of energy ?
Answer:
We are looking at alternate sources of energy because of the following reasons.

• The fossil fuels and nuclear fuels on the earth are limited which may not last for long.
• The undesirable effects of pollution, both from the burning of fossil fuels and from the radioactive nuclear wastes of nuclear power plants are creating threat to our environment.

Question 3
How has the traditional use of wind and water energy been modified for convenience ?
Answer:
(i) Wind mill farms are constructed to produce electricity.
(ii) The traditional use of energy of flowing water has been modified by establishing hydro-power plants. At hydro-power plants, the energy of falling water or flowing water is tapped by using a water turbine and then made to drive generators.

Page No.- 253

14.3 ALTERNATE OR NON-CONVENTIONAL SOURCE OF ENERGY

Question 1
What kind of mirror-concave, convex or plane – would be the best suited for use in a solar cooker ? Why ?
Answer:
A concave mirror would be best suited in a solar cooker because it focuses the sunlight in a very small area of the solar cooker and a high temperature is produced in it which is sufficient to cook the food.

Question 2
What are the limitations of the energy that can be obtained from the oceans?
Answer:
The energy from the oceans can be obtained mainly in three forms. These are
(i) tidal energy
(ii) wave energy and
(iii) ocean thermal energy

• Limitations of Tidal Energy :
  (i) There are very few sites around the world which are suitable for building tidal dams.
  (ii) The rise and fall of sea-water during high and low tides is not enough to generate electricity on a large scale.
• Limitations of wave energy : The movement of ocean waves is associated with kinetic energy. Such sites in the world are limited where the waves strike the shore lines with sufficient power.
• Limitations of ocean thermal energy : NCERT Solutions for Class 10 Science Chapter 14 Sources of EnergyTo convert ocean thermal energy into electricity, a temperature difference of 20°C (or more) between the surface water of ocean and deeper water is needed for operating OTEC power plants. This involves high cost.

Question 3
What is geothermal energy ?
Answer:
Geothermal energy can 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.

Question 4
What are the advantages of nuclear energy ?
Answer:
The advantages of nuclear energy are that :

1. Amount of energy produced per unit mass is large
2. As it does not produce any pollutants, it is clean
3. Fission of 1 atom of uranium produces 10 million times the energy that is obtained by burning 1 atom of carbon.

Page No.- 253

14.4. ENVIRONMENTAL CONSEQUENCES

Question 1
Can any source of energy be pollution free ? Why or why not ?
Answer:
No source of energy can be pollution free because even if it is clean, its assembly could have caused some environmental damage. e.g – solar cells are considered to be pollution-free. But their manufacturing may cause environmental damage.

Question 2
Hydrogen has been used as rocket fuel. Would you consider it a cleaner fuel than CNG ? Why or why not ?
Answer:
Hydrogen is cleaner fuel than CNG. This is because the burning of hydrogen produces only water, which is totally harmless. On the other hand, burning of CNG produces carbon dioxide gas and water. The carbon dioxide can produce greenhouse effect in the atmosphere and lead to the excessive heating of the environment in long run.

Page No.- 243

Question 1
Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Answer:
(i) Energy derived from biomass is a renewable source of energy because waste products are continuously produced. Plants and trees are also grown at reasonable intervals.
(ii) The energy derived from flowing water, wind, sun and ocean are renewable sources because these sources can be harnessed into energy so long as the present solar system exists.

Question 2
Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
Answer:
1. 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.

2. 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.

NCERT Solutions for Class 10 Science Chapter 14 Textbook Chapter End Questions

Question 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 cloudy day.

Question 2
Which of the following is not an example of a biomass energy source ?
(a) Wood
(b) Gobar gas
(c) Nuclear energy
(d) Coal
Answer:
(c) Nuclear energy.

Question 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) Biomass
Answer:
(a) Geothermal energy.

Question 4
Compare and contrast fossil fuels and the sun as direct sources of energy.
Answer:

Question 5
Compare and contrast biomass and hydro-electricity as sources of energy.
Answer:

Question 6
What are the limitations of extracting energy from
(a) the wind ?
(b) waves ?
(c) tides ?
Answer:
(a) Limitations of wind energy
(i) Wind energy farms cannot be established everywhere. The wind energy farms can be established only at those places, where wind blows for most part of the year.
(ii) The wind required for generating electricity should be strong and steady to maintain the desired level of generation. The minimum wind speed necessary for satisfactory working of the wind generator is about 15 km/h. This is not always so.
(iii) The wind energy farms require a large area of land.
(iv) The setting up of wind energy farms is very expensive.

(b) Limitations of wave energy : The harnessing of sea-waves energy would be a viable proposition only at those places where sea-waves are very strong. This has constraints of time and location.

(c) Limitations of tidal energy :
(i) There are very few sites around the world which are suitable for building tidal dams.
(ii) The rise and fall of sea-water during high and low tides is not enough to generate electricity on a large scale.

Question 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 sources : The sources of energy which are being produced continuously in nature and are inexhaustible, are called renewable sources of energy. The energy derived from flowing water, wind, tides, ocean waves, or wood are examples of energy from such sources.
Non-renewable sources : These sources are produced over million of years under special conditions. Once consumed, these are not replaceable for a very long time. Fossil fuels like coal, petroleum and natural gas are non-renewable sources.
(b) Exhaustible sources are non-renewable sources, while inexhaustible sources are renewable sources.
Yes, the options given in (a) and (b) are the same.

Question 8
What are qualities of an ideal source of energy ?
Answer:
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.

Question 9
What are the advantages and disadvantages of using a solar cooker ? Are there places where solar cookers would have limited utility ?
Answer:
Advantages –

1. The use of solar cooker for cooking food saves precious fuels like coal, kerosene and LPG.
2. The use of solar cooker does not produce smoke due to which it does not pollute air.
3. When food is cooked in solar cooker, its nutrients do not get destroyed. This is because in a solar cooker, food is cooked at a comparatively lower temperature.
4. In a solar cooker, up to four food items can be cooked at the same time.

Disadvantages –

1. The solar cooker cannot be used to cook food during night because sunshine is not available at that time.
2. If the day sky is covered with clouds, even then solar cooker cannot be used to cook food.
3. The direction of reflector of solar cooker has to be changed from time-to-time to keep it facing the sun.
   Sources of Energy
4. The box-type solar cooker cannot be used for baking (making chappattis, etc.) or for frying.
   The places that receive rain most of the year or where the sky remains cloudy, the solar cooker has limited utility.

Question 10
What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption ?
Answer:
Some of the environmental consequences of the increasing demand for energy are the following :

1. The combustion of fossil fuels is producing acid rain and damaging plants (crops), soil and aquatic life.
2. The burning of fossil fuels is increasing the amount of greenhouse gas carbon-dioxide in the atmosphere. It has also affected the rainfall.
3. The cutting down of trees from the forest for obtaining fire-wood is causing soil erosion and destroying wild life.
4. The construction of hydro-power plants is disturbing ecological balance.
5. Nuclear power plants are increasing radioactivity in the environment.

The following steps can be taken to reduce energy consumption :

1. Switch off lights, fans, TV. and other such electrical appliances when not needed, to save electricity.
2. Use energy efficient electrical appliances to save electricity. This can be done by using compact fluorescent lamps (CFL) and tube lights in place of conventional filament- type electric bulbs.
3. Good quality stoves should be used to burn fuels like kerosene and LPG so as to obtain maximum heat.
4. Pressure cookers should be used for cooking food to save fuel.
5. Solar cookers should be used to cook food whenever possible and solar water heaters should be used to get hot water.
6. The use of biogas as fuel should be encouraged in rural areas.
7. Bicycles should be used for short distances to save fuel like petrol which is used in cars, scooters and motorcycles.