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NCERT solutions of class 10 science chapter 14-Sources of Energy
We need energy for doing work. we get energy from the food and plants get energy from the food prepared by themselves through the process of photosynthesis ,on the similar way all the machines like fan, TV, AC, car manufacturering plants etc are required energy for doing work. We get the energy for driving various machines from the fossil fuel. but excess use of the fossil fuel will leave the earth free from these resources and over and above the issue of increasing pollution is more prevalent which is causing global warming. So just now the humans have the greatest chalange of finding the suitable sources of energy.
NCERT solutions of chapter 14 -Sources of energy
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Q1, What is a good source of energy?
Ans.A good source of energy would be one have following properties.
1.The fuel used by us would do large amount of work per unit volume or mass.
2.The fuel would be easily accessible.
3.The fuel would be easy to store.
4.It is most important that a fuel must be economical.
Q2.What is a good fuel?
Ans. A good fuel must have following qualities.
1.Proper heat be released on burning.
2.It should release least amount of smoke.
3.It should be available easily.
Q3.If you could use any source of energy for heating your food, which one would you use and why?
Ans. We use LPG, the liquid petroleum gas for heating the food since it releases larger amount of energy on heating it produces least amount of heat and easily available and most important that it is economical.
NCERT solutions of chapter 14 -sorces of energy
Page no. 348
Q1.What are the disadvantages of fossil fuels?
Ans.Burning of fossil fuel like coal and petroleum products releases carbon dioxide, carbon monoxide, nitrogen oxides sulphur dioxide. some of these gases are responsible for increasing pollution due to green house effect and some of them causes acid rain which pollutes water bodies and soil .
Q2.Why are we looking at alternate sources of energy?
Ans. The fuel coal and petroleum products are the major sources of energy, these are non-renewable sources ,thus limited in stock, it takes krores of years in their formation inside the earth over and above excess use of coal and petroleum products leads pollution which is dangerous for human health and survival of other organism like plants and animals. We are needed alternative sources of energy that could meet our requirement of energy and prevent us from increasing pollution.
Q3.How has traditional use of wind and water energy been modified for our convenience?
Ans.In past the energy of flowing water was used to provide mechanical energy like grinding the grains and wind was used for separating the grains out of chaff and lifting the ground water through a windmill. Now both of water and wind are used as a renewable source of energy for the production of electricity, hydropower plants are used, in which obstructed water(dam) preserves potential energy the falling water from a certain height is capable to rotate the rotor that moves the armature of the dynamo thereby produces electricity and energy of wind is also used to rotate the rotors of windmills and further it rotates the armature of dyomo and produces electricity.
NCERT solutions of chapter 14 -sorces of energy
Page no. 253
Q1.What kind of mirror concave, convex or plain would be the best suited for use in a solar cooker? Why?
Ans.Solar cooker is used for cooking food so concave mirror is used in it because concave mirror converge the sun rays at its focal point that increases the temperature inside it and thus accessed to cook the food.
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Q2. What are the limitations of energy that can be sustained from the ocean?
Ans. The ways of driving energy from the oceans are tidal energy, wave energy and ocean thermal energy. The tides sometimes high and low due to varying position of moon and the earth, tidal energy is harnessed by constructing a dam across a narrow opening to the sea, the turbine fixed at opening and then rising of tides gives mechanical energy to turbine which is converted into electrical energy but such areas are limited in the coast of sea.
The waves in the sea is generated by the strong winds blowing across the sea, at the sea shore by the use of devices this wave energy is utilised to rotate the turbine and producing electricity but areas of such strong waves are very limited.
There is a difference in temperature of surface water of sea and of depth, this temperature difference is utilised to run turbine of gerator and thus electricity is produced,but for the production of electricity in such a way the difference between the surface of ocean and depth should be 20 K or more
Q3. What is geothermal energy?
Ans.The heat is generated due to the collision between tectonics plates inside the earth that forms molten rocks,these molten rocks are pushed upward and trapped in certain region inside the earth ,when underground water come in contact with these hot rocks steam is generated.Sometime hot water from that region finds outlet at the earth surface ,such outlets at the earth surface known as hot springs. The steam trapped in rocks is routed through a pipe to a turbine and used to generate electricity.
Q4.What are the advantages of nuclear energy?
Ans.Nuclear energy is derived through the process of nuclear fission in which the nucleus of heavy atom is fragmented into two atoms of lighter nuclei in this process massive heat is generated,this heat is utilised to produce heat and further for the production of electricity. The fission of uraniumg atom produces 10 millions times the energy we get from the combustion of single carbon atom.
NCERT solutions of chapter 14 -sorces of energy
Page no. 253
Q1.Can any source of energy be pollution free? Why or why not?
Ans. There is not any source which is pollution free ,fossil fuels generate green house gases like carbon dioxide, carbon monoxide, nitrogen dioxide and sulphur dioxide even renewable sources are not pollution free like solar energy, actually solar energy is pollution free but the devices used for this purpose are manufactured by the industry has certain expiry and ultimately mixes with soil causing soil pollution. Nuclear energy geothermal energy wind energy also releases other types of pollutions.
Q2.Hydrogen has been used as a rocket fuel, Would you consider it a cleaner fuel than CNG? Why or why not?
Ans.Hydrogen is used as a rocket fuel that is the best alternative of fossil fuel. Hydrogen on burning produces water as a result of its reaction with atmoshpheric oxygen, while CNG on burning produces water and carbon dioxide although as compared with other fossil fuels it is least poluted .Therefore hydrogen is cleaner fuel than CNG.
NCERT solutions of chapter 14 -sorces of energy
Page no 254
Q1.Name two energy sources that you would consider to be renewable. Give reasons for choices.
Ans. The best renewable sources of energy are to be considered solar energy and geothermal energy, both sources of these energy are non -exhautible and are convenient to use and releases neglected pollution to the earth other sources of energy like ocean and wind energy are accessible only in certain areas but these sources of energy could be accessed to everywhere in the earth.
Q2.Give the names of two energy sources that you would consider to be exhautible. Give reasons for your choices.
Ans. Two sources of energy coal and petroleum products are exhaustible .Since at present most of the energy we utilise in vehicles, aeroplane ,ship and power plants comes from fossil fuels. It takes millions of years in their processing so their excess use will lead to be finished out of the earth .
NCERT solutions of chapter 14 -sorces of energy
Exercises
Q1.4 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 windi day
Ans. (b) a cloudy day
Q2.Which of the following is not an example of a biomass energy source?
(a) Wood (b) gobar gas
(c) nuclear energy (d) coal
Ans.(d) nuclear energy
Q3.Most of the sources of energy we use represent stored solar energy.Which of the following is not ultimately derived from Sunis energy.
(a) geothermal energy (b) Wind energy
(c) nuclear energy (d) bio mass
Ans. (c) nuclear energy
Q4.Compare and contrast fossil fuel and the Sun as a direct sources of energy .
Ans. Fossil fuel is exhaustible and Sun is ever green thus it’s non -exhautible source of energy
Fossil fuels are costlier than Sun’s energy.
There are limited sources of fossil fuels inside the earth and it’s biggest portion is inside the bottom of ocean which is very difficult to be explored while sun’s energy is uniformly distributed on the earth.
Fossil fuels on burning releases harmful products like CO2,CH4,NO2 and SO2 which causes air pollution .Energy of sun is derived through solar panel which releases neglected pollution .
We can use the energy of fossil fuel in all seasons but Sun’s energy can’t be used on a rainy or cloudy day.
Fossil fuels are conventional and Sun is non-conventional source of energy.
Q6.Compare and contrast bio-mass and hydroelectrity as sources of energy.
Ans. Bio-mass and hydroelectricity both are renewable sources of energy, we wouldn’t have to worry about bio-mass and hydroelectricity sources getting used up the way fossil fuels would get finished one day.
Bio-mass like wood, charcoal and biogas on burning releases harmful gases while hydroelectricity doesn’t release such gases.
Bio-mass as a biogas plant is easy and economical to install but establishing a hydroelectricity plant we are needed to build a large dam .The dams can be constructed only a limited number of places preferably in hilly areas. Large areas of agricultural land and human habitation are to be sacrificed as they get submerged. The vegetation which is submerged rots under anaerobic conditions and gives rise to large amounts of methane which is also a green house gases.
In spite of using both sources of energy bio-mass and hydroelectricity for the purpose of energy, they are used for other purposes also. The slurry in biogas plants has to be changed periodically, so it is used as a manure and large lake formed on the surface of dam is used to develop fisheries tourism and for irrigation purposes.
Q6.What are the limitations of extracting energy from –
(a) the wind? (b) waves? (c) tides?
Ans(a)The kinatic energy of wind is harnessed by the windmill. Windmills consist of a structure similar to a large electric fan that is erected at some height on a rigid support. To generate electricity, the rotatory motion of the windmill is used to turn the turbine of the electric generator. The support of a single windmill is quite small and cannot be used for commercial purposes. Therefore, a number of windmills are erected over a large area, which is known as wind energy farm. The energy output of each wind mill in a farm is coupled together to get electricity on a commercial scale. Therefore wind energy farms can be established only at those places where wind blows for the greater part of a year. The wind speed should also be higher than 15 km/h to maintain the required speed of the turbine .For a 1 MW generator ,the farm needs about 2 hectares of land. Since tower and blades of the windmill are exposed to rain sun storm and cyclone, they need a high level of maintenance.
(b) In order to extract energy from the waves, very strong ocean waves are needed.
(c) 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?
Ans(a) Renewable and non-renewable:
Renewable resources 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 resources are those which do not replenish on their own and have limited 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 quality. Like solar and wind energy.
Q8. What are the qualities of an ideal source of energy?
Ans. Following are the qualities of an ideal source of energy:
1. It should be economical
2. It should be easy available
3. Pollution free
4. Easy transportation and storage
5. The amount of energy produced when burnt should be huge.
Q9. What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?
Ans. 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.
Q10.What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Ans. 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 had 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. Reduce the unnecessary usage of electricity and water. Opt for public transportation and lessen using own vehicles. These are a few small steps that can be implemented to reduce energy consumption.
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