NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy

NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy includes answers of intext & exercise questions. All these NCERT solutions are prepared by expert teachers with detailed explanations of every important topic. It is important for the students to go through these NCERT solutions to get knowledge of the type of question asked on the Sources of Energy chapter.

NCERT Solutions for Class 10 Science Chapter 14 Intext Questions

PAGE NO. 243

Question 1: What is a good source of energy?

Answer 1: A good source of energy should have the following qualities:

  • It should be easily available.
  • It should do a large amount of work (or produce large amount of heat) per unit volume/mass.
  • It should be easy to store and transport.
  • It should be economical.
  • It should cause less environmental pollution.

Question 2: What is a good fuel?

Answer 2: A good fuel produces a large amount of heat on burning, does not produce a lot of smoke and is easily available.

Question 3: If you could use any source of energy for heating your food, which one would you use and why?

Answer 3: We shall use LPG/CNG gas or electricity for heating our food because these are efficient ways of supplying energy. Thermal efficiency of the energy source is large, there is less pollution and the source can be used easily.

PAGE NO. 248

Question 1: What are the disadvantages of fossil fuels?

Answer 1: There are following disadvantages of fossil fuels like coal and petroleum:

  • Burning of coal or petroleum causes air pollution.
  • Acidic oxides like oxides of carbon, nitrogen and sulphur are released on burning fossil fuels. These oxides lead to acid rains, which affect our water and soil resources.
  • Carbon dioxide gas also causes greenhouse effect in atmosphere.
  • Fossil fuels are non-renewable sources of energy.

Question 2: Why are we looking at alternate sources of energy?

Answer 2: Fossil fuels, which have been traditionally used by human beings as an energy sources, are non-renewable sources of energy. These sources of energy are limited and cannot replenish on their own. They are being consumed at a large rate. If this rate of consumption continues, then the fossil fuels would be exhausted from the Earth. Therefore, we should look for alternate sources of energy.

Question 3: How has the traditional use of wind and water energy been modified for our convenience?

Answer 3: To use energy of flowing water large dams are built in hilly regions to store huge amount of water at a height. The stored water from high level in dam is carried through pipes to the turbine at the bottom of the dam and runs hydropower plant. Similarly, the wind energy is used to generate electricity. For the same purpose, the rotatory motion of windmill is used to tum the turbine of the electric generator.

PAGE NO 253(A)

Question 1: What kind of mirror – concave, convex or plain – would be best suited for use in a solar cooker? Why?

Answer 1: A solar cooker uses heat of the sunlight to cook the food. A concave mirror is used in order to reflect and focus sunlight at a particular area. The mirror focuses all the incident sunlight at a point. The temperature at that point increases, thereby cooking and heating the food placed at that particular area.

Question 2: What are the limitations of the energy that can be obtained from the oceans?

Answer 2: Energy from the oceans can be obtained in the form of tidal energy, wave energy and ocean thermal energy. But these energy sources suffer from the following limitations:

  • There are very few locations where dams to utilise tidal energy can be built.
  • Cost of installation of power houses is extremely high and efficiency of plants is comparatively small.
  • Power plants built in oceans or at sea-shores will need high continuous maintenance as chances of corrosion are extremely high.

Question 3: What is geothermal energy?

Answer 3: Geothermal energy is the heat energy present inside earth in certain regions called hot spots. Due to geological changes, molten rocks formed in the deeper hot regions of earth’s crust are pushed upwards and are trapped in hot spots. When underground water comes in contact with the hot spot, steam is generated. This steam is routed through a pipe to a turbine and used to generate electricity.

Question 4: What are the advantages of nuclear energy?

Answer 4: The advantages of nuclear energy are as follows:

  • Large amount of energy is produced per unit mass.
  • It does not produce smoke. It is a clean energy.
  • Fission of one atom of uranium produces 10 million times the energy released by burning of one atom of carbon.
  • Fusion of four hydrogen atoms produces huge amount of energy.

PAGE NO 243(B)

Question 1: Can any source of energy be pollution-free? Why or why not?

Answer 1: No source of energy can be pollution-free. It is considered that solar cells are pollution-free. However, even their making causes environmental damage indirectly. Also, in the case of nuclear energy, there is no waste produced after the fusion reactions. However, it is not totally pollution-free. To start the fusion reactions, approximately 107 K temperature is required, which is provided by fission reactions. The wastes released from fission reactions are very hazardous. Hence, no source of energy is pollution-free.

Question 2: Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?

Answer 2: Hydrogen can be considered a cleaner fuel because its burning produces water vapour which is non-polluting. However, due to explosive nature of hydrogen, its storage and transportation is difficult

PAGE NO. 254

Question 1: Name two energy sources that you would consider to be renewable. Give reasons for your choices.

Answer 1: Solar energy, wind energy, ocean energy etc., are renewable sources of energy due to the following reasons:

  • These forms of energy are available in plenty in our natural environment in the form of continuous currents of energy.
  • These energy sources will not be depleted because their supply is large and extraction of usable energy from these sources is negligible.

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

Answer 2: Coal and petroleum are two exhaustible sources of energy. These fuels were formed over millions of years ago and there are only limited reserves. If we continue to use them as at present, these reserves will be exhausted very soon.

NCERT Solutions for Class 10 Science Chapter 14 Exercise 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 1: (b) a cloudy day

For solar water heater to work, sunlight is required and on a cloudy day, the sunlight is not available.

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 2: (c) nuclear energy

Nuclear energy is not an example of a biomass energy source. The biomass energy sources are wood, coal, cow dung, gobar-gas etc.

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 3: (c) Nuclear energy

Nuclear energy is related to fission or fusion of a nucleus which does not involve the sun’s energy.

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

Answer 4: The sun is the main source of energy for all living beings on this earth. Even the energy in fossil fuels has come from the sun. When green plants prepare food, they convert solar energy into chemical energy which is stored in the form of biomass. The same biomass gets transferred to the animals. Thus, the energy in the form of biomass which is stored in fossil fuels has come from the sun.

Question 5: Compare and contrast biomass and hydroelectricity as sources of energy.

Answer 5: Hydroelectricity is generated using the kinetic energy from moving water, while the energy from biomass is generated by decomposition of farm waste. Since biomass is composed of organic compounds so energy from biomass results in air pollution. Hydroelectricity, on the other hand, is pollution free.

Question 6: What are the limitations of extracting energy from—

(a) the wind?
(b) waves?
(c) tides?

Answer 6:

(a) Wind flowing with sufficient speed is not available everywhere and all the time. Thus, wind is not a dependable source of energy. The kinetic energy of wind (wind energy) can be used only at the site of the windmill.

(b) Wave energy would be commercially viable only at places where the waves are strong. The energy produced from waves has to be transmitted through long distances at the possibility of use.

(c) There are very few sites suitable for harnessing tidal energy. The rise and fall of water during tides is not very large. So, the large-scale generation of electricity is not possible.

Question 7: On what basis would you classify energy sources as
(a) renewable and nonrenewable?
(b) exhaustible and inexhaustible?
Are the options given in (a) and (b) the same?

Answer 7: Options given in (a) and (b) are almost the same.

Renewable sources or inexhaustible of energy are those which can be generated by us or which are constantly being generated by natural processes or whose supply is unlimited. On the other hand, the energy source which cannot be renewed in the foreseeable future are called non-renewable or exhaustible sources of energy. 

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

Answer 8: Followings are the qualities of an ideal source of energy:

  • It should do a large amount of work per unit volume or mass.
  • Which would be easily accessible. 
  • Which would be easy to store and transport.
  • be economical.

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

Answer 9: The advantages of the solar cooker are:

  • The cost of making such a cooker is very less. 
  • The food never gets burnt in this type of cooker and stays hot.

The disadvantages of the solar cooker are:

  • This type of cooker cannot be used for frying or preparing chapatis. 
  • This device cannot be used at night for preparing food.

In a colder climate where there is not enough sunshine all year, the solar cooker would have very 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 10: Environmental consequences of increasing demand for energy are as follows:

  • Use of fossil fuels is increasing air pollution which is not good for our health.
  • The greenhouse effect has resulted in global warming which is manifesting itself in strange changes in the weather pattern around the world.

Steps to reducing energy consumption:

  • Use public transport instead of private modes of transport, use a bicycle whenever possible.
  • Avoid unnecessary use of modern gadgets which consume a lot of energy.
  • Use of more renewable and eco-friendlier source of energy such as solar and wind energy.

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