We have Provided the NCERT/CBSE Solutions chapter-wise for Class 10 Science Chapter 14 Sources of Energy with Answers by expert subject teacher for latest syllabus and examination. Students can take a free NCERT Solutions of Sources of Energy. Each question has right answer Solved by Expert Teacher.
CBSE Solutions Class 10 Science Sources of Energy
Page No. 243
Questions
Q1. What is a good source of energy?
Answer: A good source of energy has the following characteristics:
- It should be capable of delivering desired quantity of energy at a steady rate over a long period of time
- It must be convenient to use
- It must be easy to transport and store
- It doesmot cause environmental pollution
Q2. 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.
Q3. If you could use any source of energy for heating your food, which one would you use and why?
Answer: Natural gas can be used for heating and cooking food because it is a clean source of energy. It does not produce huge amount of smoke on burning. Although it is highly inflammable, it is easy to use, transport, and it produces a huge amount of heat on burning.
Page No. 248
Questions
Q1. What are the disadvantages of fossil fuels?
Answer: The following are some of the downsides of fossil fuels:
- Coal and petroleum combustion produce a lot of pollutants, which pollute the air.
- Fossil fuels emit carbon, nitrogen, sulphur, and other oxides that generate acid rain, which has an impact on soil fertility and potable water.
- The combustion of fossil fuels emits gases such as carbon dioxide, which contribute to global warming.
Q2. Why are we looking at alternate sources of energy?
Answer: Fossil fuels which are traditionally used by human beings everywhere as an energy sources are non-renewable sources of energy. These sources of energy are limited and will disappear after some time. They are being consumed at a large rate. Therefore, we should conserve the energy sources. Hence, we should look for alternate sources of energy.
Q3. How has the traditional use of wind and water energy been modified for our convenience?
Answer: The kinetic energy of the wind can be used to do work. This energy was harnessed, by windmills in the past to do mechanical work such as in a water lifting pump. The rotatory motion of windmill is utilised to lift water form a well. But nowadays, wind energy is used to generate electricity. To generate electricity, the rotatory motion of the windmill is used to turn the turbine of the electric generator.
The kinetic energy of flowing water or potential energy of water at a height can be converted into electricity. The hydropower plants are associated with dams. The water from the high level in the dam is carried through pipes, to the turbine and thus electricity is generated.
Page No. 253
Questions
Q1. What kind of mirror – concave, convex or plain – would be best suited for use in a solar cooker? Why?
Answer: Concave mirror, because it focusses the sun rays at a point to raise the temperature at that point.
Q2. 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
- 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.
Q3. What is geothermal energy?
Answer: The energy of the earth due to its internal heat which can be used as source of energy under some suitable conditions caused by natural action is called geothermal energy.
Q4. 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.
Questions
Q1. Can any source of energy be pollution-free? Why or why not?
Answer: No source of energy can be pollution-free. Every source of energy has some type of pollution. For example, the wastes of nuclear reaction are very dangerous to the environment.
Q2. 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 less polluting than compressed natural gas (CNG). Hydrocarbons are used to make CNG. As a result, it contains carbon. A form of CNG pollutant is carbon. Hydrogen, on the other hand, produces no waste. There is no waste produced by hydrogen fusion. As a result, hydrogen is more environmentally friendly than CNG.
Page No. 254
Questions
Q1. Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Answer: Two renewable sources of energy are :
(i) Sun: The energy derived from the Sun is known as solar energy. Solar energy is produced by the fusion of hydrogen into helium, fusion of helium into other heavy elements, and so on. A large amount of hydrogen and helium is present in the Sun. The Sun has billions years more to burn. Therefore solar energy is a renewable source of energy.
(ii) Wind: Wind energy is derived from fast blowing air. Wind energy is harnessed by windmills in order to generate electricity. Air blows because of uneven heating of the Earth. Since the heating of the Earth will continue forever therefore wind energy will also be available forever.
Q2. Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
Answer: Exhaustible energy sources :
(i) Coal, (ii) Petroleum.
Because if these sources are consumed, they will get exhausted.
Page No. 254
Exercise
Q1. 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
Page No: 255
Q2. 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
Q3. 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
Q4. Compare and contrast fossil fuels and the Sun as direct sources of energy.
Answer:
- Energy of fossil fuels comes from the solar energy. However, fossils fuels are the non-renewable sources of energy. On the other hand, sun is a renewable source of energy.
- Fossil fuels cause pollution but solar energy does not cause pollution.
- Energy is supplied by fossil fuels at any time of the day but sun supplies energy only when it shines.
Q5. Compare and contrast bio-mass and hydro electricity as sources of energy.
Answer:
| Biomass | Hydroelectricity |
| (i) Renewable source of energy. (ii) Biomass plants can be installed at any place to produce biomass as energy source. (iii) To collect waste materials is a tough and costly process. | (i) Renewable source of energy. (ii) Plants can be installed only at the places where dams can be constructed. (iii) Once the plants start to work, it is not difficult to collect water. |
Q6. 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.
Q7. 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) The source of energy that replenishes in nature is known as renewable source of energy. Sun, wind, moving water, bio-mass, etc. are some of the examples of renewable sources of energy.
The source of energy that does not replenish in nature is known as non-renewable source of energy. Coal, petroleum, natural gas, etc. are some of the examples of non-renewable sources of energy.
(b) Exhaustible sources are those sources of energy, which will deplete and exhaust after a few hundred years. Coal, petroleum, etc. are the exhaustible sources of energy.
Inexhaustible resources of energy are those sources, which will not exhaust in future. These are unlimited. Bio-mass is one of the inexhaustible sources of energy.
Yes. The options given in (a) and (b) are the same.
Q8. What are the qualities of an ideal source of energy?
Answer: An ideal source of energy must be:
- cost-effective,
- easily accessible,
- smoke- and pollution-free,
- simple to store and transport,
- capable of producing massive amounts of heat and energy when burned.
Q9. What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?
Answer: Solar cooker uses Sun’s energy to heat and cook food. It is inexhaustible and clean renewable source of energy. It is free for all and available in unlimited amount. Hence, operating a solar cooker is not expensive.
Disadvantage of a solar cooker is that it is very expensive. It does not work without sunlight. Hence, on cloudy day, it becomes useless.
The places where the days are too short or places with cloud covers round the year, have limited utility for solar cooker.
Q10. What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Answer: We have studied a large number of sources of energy. Exploiting any source of energy disturbs the environment in some way or the other. In any given situation, the source we would choose depends on factors such as the ease of extracting energy from that source, the economics of extracting energy from the source,
The efficiency of the technology available and the environmental damage that will be caused by using that source. We have already seen that burning fossil fuels causes air pollution Research continues in these areas to produce longer lasting device that will cause less damage throughout their life.
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