NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy

NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy

NCERT Questions

In Text Questions

Question 1.
What is good source of energy ?
Answer:
A substance which produces sufficient amount of energy over a long period of time without producing much smoke is known as good source of energy. Characteristics of a good source of energy.

Question 2.
What is good fuel ?
            Or
What is a fuel ?
Answer:
A fuel which provides large amount of heat energy without causing pollution.

Question 3.
If you could use any source of energy for heating your food, which one would you use and why ?
Answer:
We would use microwave oven for heating our food. This is because the nutritional value of food is not lost when heated in a microwave oven.

Question 4.
What are the disadvantages of fossil fuels ? (CBSE 2010)
Answer:

1. They cause environmental pollution.
2. They cause global warming.
3. They do not supply enough heat energy.
4. The by-products of burning fuels cause acid rain which pollute water resources.

Question 5.
Why are we looking at alternate sources of energy ?
                                                      Or
State one reason that has necessitated to look for alternate sources of energy ? (CBSE 2013)
Answer:
Because the conventional sources of energy may completely be exhausted one day if their use at the present rate continues.

Question 6.
How has the traditional use of wind energy and water been modified for our convenience
(CBSE 2010, Term I)
Answer:
These energies have been converted into electrical energy using electric generators.

Question 7.
What kind of mirror—concave, convex or plane would be best suited for the 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.

Question 8.
What are the limitations of the energy that can be obtained from oceans ? (CBSE 2010)
                                                      Or
List any four limitations of the energy obtained from oceans. [CBSE (All India) 2009, 2012]
Answer:

1. Energy from oceans is available only when high tides are in the ocean.
2. Power plants used to convert ocean energy into electric energy do not operate continuously.
3. Energy of ocean waves can be extracted blow all times across the ocean.
4. Tidal power plants can not be installed everywhere.

Question 9.
What is geothermal energy ? (CBSE 2010, Term I, 2011, 2012)
Answer:
The heat energy stored in the hot spots of the earth’s crust is called geothermal energy.

Question 10.
What are the advantages of nuclear energy ?
Answer:

1. A small quantity of nuclear fuel gives a large amount of energy.
2. In a nuclear power plant, the nuclear fuel is inserted once to get energy over a longer period of time.

Question 11.
Can any source of energy be pollution free ? Why or why not ?
Answer:
No source of energy is there which is pollution free. However, some sources of energy cause more pollution and some sources of energy cause less pollution.

Question 12.
Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not ?
Answer:
Hydrogen causes less air pollution than C.N.G. because burning of hydrogen produces water vapours and burning of CNG produces CO₂. When the concentration of CO₂ increases in the atmosphere, then the temperature of the atmosphere increases. This effect is known as green house effect. The increased temperature of the atmosphere affects life on the earth.

Question 13.
Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Answer:

1. Bio-mass is considered as a renewable source of energy because forests can be replenished.
2. Water is also a renewable source of energy as water is continuously available to use due to water cycle in nature.

Question 14.
Give the names of two energy sources that you would consider to be exhaustible.
Answer:
Give reasons for your choices,

1. Coal
2. Petroleum.

They will be exhaustible when continuously extracted. Moreover, the formation of these fuels under the earth takes a longer period of time.

NCERT Chapter End Exercises

Question 1.
A solar 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).

Question 2.
Which of the following is not a example of a bio-mass energy source ?
(a) wood,
(b) gobar gas,
(c) fossil fuels,
(d) bio-mass. (Bihar Board 2012)
Answer:
(c).

Question 3.
Most of the sources of energy we use represent stored solar energy. Which of the following is not ultimately derived from the Suns energy ?
(a) geothermal energy,
(b) wind energy,
(c) fossil fuels,
(d) bio-mass.
Answer:
(a).

Question 4.
Compare and contrast fossil fuels and the Sun as a source of energy.
Answer:

1. 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.
2. Fossil fuels cause pollution but solar energy does not cause pollution.
3. Energy is supplied by fossil fuels at any time of the day but sun supplies energy only when it shines.

Question 5.
Compare and contrast bio-mass and hydro-electricity as source of energy.
Answer:

Bio-mass	Hydro electricity
(i)    The energy supplied by the burning of bio-mass causes pollution.  (ii)    The energy from bio-mass can be obtained by burning it directly or by a gobar gas plant.	(i)     Hydro-electricity does not cause pollution.  (ii)    Hydro-electricity can be obtained by constructing costly dams.

Question 6.
What are the limitations of extracting energy from
(a) the wind
(b) Waves
(c) Tides ?
Answer:
(a)

1. We cannot depend upon wind energy as it is available only when strong wind blows. The appliances or machines operating with wind energy stop working as soon as wind stops. The minimum speed of wind to operate generator to produce electricity is 15 km/h.
2. Wind energy is not sufficient to operate heavy machines.
3. The use of wind energy is limited to certain places where strong winds blow most of the time.

(b) Energy of waves can be extracted only if strong winds blow all the time across the sea.
(c) Tidal power plant can extract energy from the waves only when the difference between the water levels of high tide and low tide is very large.

Question 7.
On what basis you classify energy source as
(a) Renewable and non-renewable ?
(b) Exhaustible and inexhaustible ?
(c) Are the options given in (a) and (b) the same ?
Answer:
(a) Renewable Sources of Energy are those which are continuously supplied by nature. For example, the sun, the wind.
(b) Non-Renewable Sources of Energy are those which have been formed in nature long ago under certain conditions of temperature and pressure. Non-renewable sources of energy take longer period of time for their formation. For example, fossil fuels like coal, petroleum.
(c) Inexhaustible Sources of Energy are those which supply continuous energy for unlimited time. In fact, exhaustible sources of energy are also termed as non-renewable energy sources. But wood is an exception as it can be made renewable by growing more plants periodically. Inexhaustible sources of energy are termed as renewable sources of energy.

Question 8.
What are qualities of an ideal source of energy ?
                                               Or
Write any two characteristics of a good source of energy. (CBSE 2013)
Answer:

1. It supplies useful energy continuously.
2. It does not cause environment pollution.
3. It is economical.

Question 9.
What are the advantages and disadvantages of using a solar cooker ? Are there places where solar cookers would have limited utility ? (CBSE 2010)
Answer:
Advantages:

1. There is no cost of cooking food in a solar cooker.
2. No pollution is caused when food is cooked in a solar cooker.
3. Nutrition value of food is preserved when food is cooked in the solar cooker.
4. Two or three dishes can be cooked at a time.

Disadvantages:

1. Food cannot be cooked at night and on a cloudy day using a solar cooker.
2. The cost of making solar cooker is high.
3. Food cannot be cooked quickly with the solar cooker.
4. Large quantity of food cannot be cooked with a solar cooker.
5. Chapatis cannot be made with solar cooker.
   Solar cooker will have limited utility at places where the sun shines for shorter period of time or where the sun rays never reach.

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

1. More use of fossil fuels for fulfilling the increasing demand for energy is polluting air (i.e. the environment),
2. LPG and CNG are considered as clean fuels but the extraction and transportation of these fuels cause environmental pollution.
3. The use of large number of sources of energy is causing global warming.

NCERT Exemplar Solutions for Class 10 Science Chapter 14 Sources of Energy

Question 1.
Which of the following is a non-renewable source of energy ?
(a) Wood
(b) Sun
(c) Fossile fuels
(d) Wind
Answer:
(c).

Question 2.
Acid rain happen because
(a) Sun leades to heating of upper layer of atmospher
(b) burning of fossil fuels release oxides of carbon, nitrogen and sulphur in the atmosphere
(c) electrical charges are produced due to friction amongst clouds
(d) earth atmosphere contains acids.
Answer:
(c).
Explanation : When oxides of carbon, nitrogen and sulphur react with water vapours in the atmosphere, they form carbonic acid, nitric acid and sulphuric acid respectively. These acids come down to the earth with rain.

Question 3.
The rain containing these acids is called acid rain.
Fuel used in thermal power plants is
(a) water
(b) uranium
(c) biomass
(d) fossil fuels
Answer:
(c).

Question 4.
In a hydro power plant
(a) Potential energy possessed by stored water is converted into electricity
(b) Kinetic energy possessed by stored water is converted into potential energy
(c) Electricity is extracted from water
(d) Water is converted into steam to produce electricity
Answer:
(a).
Explanation : Sequence of energy transformation in hydro power plant :

Question 5.
Potential energy of water stored in a dam Kinetic energy of falling water -» K.E. of rotation of turbine -> electrical energy. Which is the ultimate souce of energy ?
(a) Water
(b) Sun
(c) Uranium
(d) Fossil fuels
Answer:
(b).
Explanation : All forms of energy are derived from the sun.

Question 6.
Which one of the following of energy leads to least environmental pollution in the process of its harnessing and ultisation ?
(a) Nuclear energy
(b) Thermal energy
(c) Solar energy
(d) Geothermal energy
Answer:
(c).

Question 7.
Ocean thermal energy is due to
(a) energy stored by waves in the ocean
(b) temperature difference levels in the occean
(c) pressure difference at different levels in the ocean
(d) tides arising out in the ocean
Answer:
(b).

Question 8.
The major problem in harnessing nuclear energy is how to
(a) split nuclei ?
(b) sustain the reaction ?
(c) dispose off spent fuel safely ?
(d) convert nuclear energy into electrical energy ?
Answer:
(c).
Explanation : This is because even spent fuel (nuclear waste) continues to emit harmful radiation.

Question 9.
Which part of the solar cooker is responsible for green house effect ?
(a) Coating with black colour inside the box
(b) Mirror
(c) Glass sheet
(d) Outer cover of the solar cooker
Answer:
(c).
Explanation : Green house effect in a region occurs when heat radiation (infra-red radiation) are trapped in that region. When sunlight enters the solar cooker through a glass sheet, then the objects inside the solar cooker emit heat radiation (or infra-red radiation) due to their increased temperature. These radiations have long wavelengths and hence less energy. Therefore, they cannot pass through the glass sheet. Hence, interior of the solar cooker becomes warm due to the trapping of these radiation.

Question 10.
The main constituent of biogas is
(a) methane
(b) carbon dioxide
(c) hydrogen
(d) hydrogen sulphide
Answer:
(a).

Question 11.
The power generated in a windmill
(a) is more in rainy season since damp air would mean more air mass hitting the blades
(b) depends on the height of the tower
(c) depends on wind velocity
(d) can be increased by planting tall trees close to the tower
Answer:
(c).

Question 12.
Choose the correct statement
(a) Sun can be taken as an inexhaustible source of energy
(b) There is infinite storage of fossil fuel inside the earth
(c) Hydro and wind energy plants are non polluting sources of energy
(d) Waste from a nuclear power plant can be easily disposed off
Answer:
(a).

Question 13.
In a hydroelectric power plant more electrical power can be generated if water falls from a greater height because
(a) its temperature increases
(b) larger amount of potential energy is converted into kinetic energy
(c) the electricity” content of water increases with height
(d) more water molecules dissociate into ions
Answer:
(b).

Question 14.
Choose the incorrect statement regarding wind power
(a) It is expected to harness wind power to minimum in open space
(b) The potential energy content of wind blowing at high altitudes is the source of wind power
(c) Wind hitting at the blades of a windmill causes them to rotate. The rotation thus achieved can be ultilised further
(d) One possible method of ultilising the energy of rotational motion of the blades of a windmill is to run the turbine of an electric generator
Answer:
(b).

Question 15.
Choose the incorrect statement
(a) We are encouraged to plant more trees so as to ensure clean environment and also provide bio-mass fuel i
(b) Gobar-gas is produced when crops, vegetable wastes etc., decompose in the absence of oxygen
(c) The main ingredient of bio-gas is ethane and it gives a lot of smoke and also produces a log of residual ash
(d) Bio-mass is a renewable source of energy
Answer:
(c).

Question 16.
Why is there a need to harness non-convential sources of energy ? Give two main reasons.
Answer:

1. Non-conventional sources of energy are pollution free, whereas fossil fuels cause lot of pollution.
2. Non-conventional sources of energy are in exhaustible, whereas fossil fuels are limited.
3. Our demand of energy is increasing day by day.

Question 17.
Write two different ways of harnessing energy from occean.
Answer:

1. Tidal energy.
2. Ocean Thermal energy (OTEC).

Question 18.
What steps would you suggest to minimise environmental pollution caused by burning of fossile fuel ?
Answer:
We can minimize environmental pollution caused by the burning of fossil fuel by

1. growing more and more trees,
2. Using smokeless chulahs and
3. smokeless chimneys in thermal power plants.

Question 19.
What is the role of a plane mirror and a glass sheet in a solar cooker ?
Answer:
A solar cooker covered by a plane glass slab will be more efficient.
This is because glass slab does not allow the heat radiation to escape from the solar cooker and hence the temperature of the solar cooker covered with glass slab increases more than the temperature of the solar cooker which is left open.

Question 20.
Mention three advantages of a solar cell ?
Answer:
Advantages of Solar Cells

1. They directly convert solar energy into electrical energy.
2. They are environment-friendly i.e. they do not cause pollution.
3. They are used to operate electric bulbs and tubes in remote areas where hydro—electricity is not available.

Question 21.
What is biomass ? What can be done to obtain bio-energy using biomass ?
Answer:
A material which contains carbon and other combustible materials is called biomass. The waste of plants and animals is the example of bio mass. (CBSE Papers)

Question 22.
What are the limitation in obtaining energy from wind ?
Answer:

1. We cannot depend upon wind energy as it is available only when air is in motion. The appliances or machines operating with wind energy stop working as soon as wind stops. The minimum speed of wind to operate generator to produce electricity is about 15 km/h. As soon as the speed of the wind becomes less than 15 km/h, the generator stops working.
2. There are certain regions where wind is not available, so the use of wind energy is limited to certain places where wind is in plenty and blows most of the time.
3. Wind energy is not sufficient to operate very heavy machines.
4. Wind energy cannot be used to operate all types of machines.
5. Wind mills are usually broken during storms and hence lot of money is spent for the maintenance of a wind energy form.

Value Based Questions in Science for Class 10 Chapter 16 Management of Natural Resources

Question 1.
Your father has a car. He can also afford to hire a driver. Even then he sends you in school bus. What is the rationale behind it ?
Answer:
It is saving on natural resources for which your father insists on your going to school in the school bus. The bus has to make trip to school. There will be no extra gasoline consumption if you go to school in the bus. Going by car will consume gasoline. If every student who can afford goes in a car, the consumption of gasoline will go up several times. It is because of this reason that many offices maintain cabs for bringing the employees to the work place. It is just similar to our campaign to save electricity (by putting off light and gadgets not in use) or water (by turning off the tap when water is not required).

Question 2.
CFL is quite costly as compared to incandescent electric bulb. Even then we read that incandescent bulbs should be replaced by CFLs. Why so ?
Answer:
CFL or compact fluorescent lamp consumes one fifth of energy as compared to incandescent bulb. It also produces less heat and is therefore, environmental friendly. The extra money spent on purchasing a CFL will be recovered in the form of lesser energy bill for the consumer. Use of CFLs will help in less consumption of the resource resulting in its greater availability.

Question 3.
What is the social impact of technique developed by Rajinder Singh in Rajasthan ?
Answer:
Rajinder Singh, popularly known as “Water Man of Rajasthan” developed the technique of underground dams for storing run off and rain water. They were connected to surface water tanks as well as crop fields by means of underground channels. The stored water is used for irrigating crop fields throughout the year in areas where water availability is scarce even for drinking.

Question 4.
Your school keeps dust/garbage bins at many places outside the class rooms where the students and the teachers can dump their waste food, waste paper, used pens, pencil shavings, plastic bags, aluminium foils, empty mineral water bottles, etc. The garbage bins are emptied by the school sweeper in larger container of municipal committee for taking away to dumping ground. What improvement would you suggest ?
Answer:
Instead of common garbage bin, I will suggest keeping of two bins, green bin for easily biodegradable articles like waste food, and blue bin for slow decaying and nonbiodegradable articles. The green bins should not be emptied in the container of municipal committee but in a pit inside the school campus for preparing manure for the plants. The blue bins could be emptied in the municipal committee container.
While discussing about coal and petroleum, a teacher told the students about PCRA’s (Petroleum Conserva¬tion Research Association) guidelines to save the fossil fuels while driving vehicles. Deepa was going to her school with her mother who was driving car. At the traffic signal, when the light was red, Deepa suggested her mother to switch off the engine.

Question 5.
After reading the above passage, answer the following questions :
(a) Fossil fuels are natural reserves, then why we need to conseve them ?
(b) List any two ways of saving the fossil fuels
(c) State two values exhibited by Deepa. (CBSE Foreign 2016)
Answer:
(a) Fossil fuels take millions of years for their formation. Their present stock is limited and hence exhaustible. They should be conserved to provide for their availability for future generations.
(b)

1. Using public transport
2. Walking short distances.
3. Use of fuel efficient technology in vehicles.

(c) Deepa exhibited concern for

1. Conservation of natural resource,
2. Reduction in environmental pollution
3. Assertion for global cause.

Question 6.
The activities of man had adverse effects on all forms of living organisms in the biosphere. Unlimited exploi¬tation of nature by man disturbed the delicate ecological balance between the living and nonliving compo¬nents of the biosphere. The unfavourable conditions created by man himself threatened the survival not only of himself but also of the entire living organisms on the mother earth. One of your classmates is an active member of “Eco Club” of your school which is creating environmental awareness amongst the school students, spreading the same in the society and also working hard for preventing ènvironmental degradation of the surroundings.
(a) Why is it necessary to conserve our environment ?
(b) State the importance of green and blue dust bins in the safe disposal of house hold waste.
(c) List two values exhibited by your classmate who is an active member of Eco Club of your school.  (CBSE A.I. 2016)
Answer:
(a) Conservation of Environment:

1. Protection of air, soil and biota from pollutants,
2. Maintenance of ecological balance,

(b) Importance of Green Blue Dust Bins. Green dust bins are meant for putting in biodegradable wastes while blue dust bins are used for non-biodegradable wastes. Segregation of the two types of wastes and putting them in separate dust bins helps in quicker disposal of wastes,
(c) Values Shown by Classmate:

1. Concern for cleanliness of the surroundings.
2. Quicker and proper disposal of wastes.
3. Concern for environment.
4. Civic sense.

HOTS Questions for Class 10 Science Chapter 14 Sources of Energy

Question 1.
Following model demonstrates the process of thermo-electric production.

1. Identify and label the device marked as 1.
2. Why is tennis ball fitted with metal sheets rotated ?
3. Name the device, which depends on the principle demonstrated by this model.
4. Which form of energy is converted into electrical energy ?

Answer:

1. Device 1 is a dynamo.
2. Tennis ball fitted with metal sheets rotates due to the force exerted on it by the steam.
3. Thermal power plant works on the principle demonstrated by the given model.
4. Mechanical energy of tennis ball fitted with metal sheets is converted into electrical energy.

Question 2.
A diagram shown below is a biogas plant.

1. Identify the parts indicated by question marks and labelled 1, 2, 3 and 4 in the diagram.
2. Name the micro organisms responsible for the fermentation of the slurry in the digester.
3. Name two chemical elements present in the manure or spent slurry.

Answer:

1. 1. Slurry of cattle dung and water
   2. Gas tank containing bio-gas.
   3. Digester.
   4. Spent slurry or manure
2. Anaerobic micro organisms,
3. Nitrogen and phosphorous are present in the manure.

Question 3.
A student constructed a box type solar cooker. He found that it did not work efficiently. What could this be due to ? Give any four possible mistakes in the solar construction and operation of the cooker. What maximum temperature can ordinarily be reached inside a solar cooker ? (CBSE 2010)
Answer:
He might be committing the following mistakes :

1. He might have not blackened the interior of the solar cooker,
2. He might be using a plastic cover instead of a glass cover,
3. He might have not made it insulated,
4. He might have not used black containers. Maximum temperature attained in a solar cooker is about 140° C.

Question 4.
A student has set up a solar cooker in a box by using a black painted aluminium sheet, a black cooking vessel, some glass wool, a glass sheet and a mirror plate. What is the role of each item used in the solar cooker ?
Answer:
Black painted aluminium sheet absorbs heat radiation.
Black cooking vessel also absorbs heat radiation to cook food.
Glass wool prevents the loss of heat.
Glass sheet prevents the escape of heat radiation from the box.
Mirror plate reflects the sunlight to fall on the glass sheet.

 

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