Sources of Energy Class 10 Important Questions with Answers Science Chapter 14

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Class 10 Science Chapter 14 Important Questions with Answers Sources of Energy

Class 10 Chemistry Chapter 14 Important Questions with Answers Sources of Energy

Sources of Energy Class 10 Important Questions Very Short Answer Type

Question 1.
Define a solar panel. (2012)
Answer:

• A large number of solar cells joined together in a definite pattern is called a solar panel.
• A solar panel can provide much more electric power than a single solar cell.

Question 2.
Why is the outer surface of a solar cooker blackened? Name one more such device. (2012)
Answer:
The outer surface of a solar cooker is blackened because the black colour is a very good absorber of heat. So, the black surface absorbs maximum heat rays of the sun.
Another solar device. Solar water heater.

Question 3.
Mention any one reason due to which most of the thermal power plants are set up near coal or oil fields. (2013)
Answer:
It is easier to transmit electricity over long distances than to carry coal, oil or gas over the same distance, therefore many thermal power plants are established near coal or oil fields.

Question 4.
Write the characteristic features of the micro organisms which help in the production of biogas in a biogas plant (2013)
Answer:
The production of biogas in a biogas plant is carried out by anaerobic bacteria which carry out decomposition in the presence of water but in the absence of oxygen.

Question 5.
What are hot spots inside earth’s crust? (2014)
Answer:
Due to geological changes, molten rocks formed in the deeper hot regions of earth’s crust are pushed upward and trapped in certain regions. These are called ‘hot spots’.

Question 6.
Mention the purpose of blackening the interior of a solar cooker. (2014)
Answer:
The black painted surface is used in the interior of a solar cooker because black surface absorbs more heat rays of the sun.

Question 7.
Define the process of nuclear fission. (2015)
Answere:
The splitting of nucleus of a heavy atom when bombarded with low-energy neutrons into lighter nuclei along with the release of large amount of energy.

Question 8.
Name the part of a biogas plant where reactions take place in the absence of oxygen. (2015)
Answer:
Digester tank

Sources of Energy Class 10 Important Questions Short Answer Type

Question 1.
Draw schematic labelled diagram of box type solar cooker.
Name two components of solar cooker which are responsible to increase the temperature inside the solar cooker. Explain their function. (2012)
Answer:
Solar cooker is a device used to trap solar energy and utilize it to cook food. It consists of a box painted black from inside to absorb heat of the Sun (black colour is the best absorber of heat). A thick glass lid is placed over the box to trap heat energy of the Sun. A plane mirror reflector is also attached to the box so that a strong beam of sunlight falls over the cooker’s top.

(i) The reflector of the solar cooker sends strong beams of sunlight over the top of the cooker. Sunlight consists of about 1/3 of infrared rays which have a heating effect. These infrared rays are of shorter wavelength as these are produced by a very hot source of heat.

(ii) The glass lid over the cooker allows these infrared rays of short wavelength into the cooker but does not allow the infrared rays which are emitted by the black surface of the cooker to escape (due to green house effect) as these are of longer wavelength. Thus, heat energy of the Sun gets trapped in the black box of the solar cooker. This heat cooks the food material kept in the black box.

Question 2.
(a) List four factors that should be taken into consideration in the choice of a good source of energy.
(b) How does burning of fossil fuel cause water pollution? (2012)
Answer:
(a) A good source of energy:

1. It releases a large amount of energy per unit volume or mass.
2. It is easily accessible.
3. It is easy to store and transport.
4. It is quite economical to use.

(b) The burning of fossil fuels produces acidic gases such as sulphur dioxide and nitrogen oxides. These acidic gases cause acid rain. The acid rain makes the water of lakes and rivers acidic. The acidic water of the lakes and rivers becomes dangerous for aquatic life.

Question 3.
(a) Name three fossil fuels.
(b) Write two advantages of fossil fuels.
(c) Give one reason to explain the need to conserve fossil fuels. (2013)
Answer:
(a)

1. Coal
2. Petrol and
3. Diesel

(b) Advantages of fossil fuels:

• Fossil fuels are used directly in homes, transport vehicles and industry. They.have a high calorific value.
• Fossil fuels are the major source of energy for generating a huge amount of electricity in power plants.

(c) Need to conserve fossil fuels. The fossil fuels have been used at such a fast pace that only limited reserves of these fuels are now left on earth. These fuels will soon get exhausted and since fossil fuels were formed very slowly over the past millions of years, therefore fossil fuels need to be conserved for the future generations.

Question 4.
Ramu has a piece of agricultural land in a village. He decides to set up a brick factory on it. His friend Shyam persuades him to change his decision in the interest of village because presence of a factory would severely affect the health of villagers as well as agricultural produce of others. Ramu understands and abandons his plans.
Explain how these values helped Shyam to save interests of his village? (2013)
Answer:
(i) The agricultural land converted into a manufacturing factory directly affects the crop production as large amounts of fertile soil, will be converted into solid bricks.

(ii) The factory requires burning of fossil fuels which produces a large amount of carbon dioxide which damages and pollutes the environment thereby affecting the health of the villagers.

(iii) The burning of coal in the factory leaves behind a lot of ash. It also puts tiny particles of ash (fly-ash) into the air causing air pollution.

It is because of these important factors that Shyam is able to convince Ramu for not converting his agricultural land into a brick manufacturing factory and thus protects the villagers and surrounding environment.

Question 5.
List any three qualities of an ideal source of energy. (2014)
Answer:
Qualities of an ideal source of energy:

1. It should produce large amount of heat per unit volume or mass.
2. It should not produce ash and harmful gases on burning.
3. It should be economical and easily available.

Question 6.
Nikhil and Neha went to a remote village in Kerala to meet their grandmother. They were surprised to see a biogas plant in Mr. Nair’s house in the neighbourhood. There were plenty of livestocks and the household used cooking gas from the plant. Also their farm had rich vegetation. They contacted the sarpanch of the village and convinced him to set up a biogas plant for the village community.  (2014)
Explain the possible arguments given by Nikhil and Neha to the Sarpanch to convince him to set up a community biogas plant.
Answer:
Nikhil can explain the following advantages to the sarpanch to convince him:

• Farmers can produce clean domestic fuel from wastes like animal dung, dry leaves, dry plants, etc.
• Spent slurry can be used in the fields as manure to increase the fertility of the soil.
• Biogas can be used to generate electricity which can be utilized to run modern machines used in the fields to save time and energy of the farmer and also increase the yield of the crop.

Question 7.
Write any three characteristics of a good fuel. (2014)
Answer:

1. A good fuel should have a high calorific value. It means it gives more heat per unit mass.
2. It should burn without giving out any smoke or harmful gases. So that it does not pollute air on burning.
3. The ignition temperature of an ideal fuel should neither be too low nor too high because if the ignition temperature of the fuel is very low, then the fuel will catch fire too easily and hence it will be very unsafe to use it. If the ignition temperature is too high, then it will be very difficult to light the fuel.

Question 8.
Anita visited her village during summer vacation and saw her grandmother burning firewood to cook food. This caused lots of smoke and resulted in the bad health of Anita’s grandmother. Anita suggested some alternatives to her family in the village and offered to help them. Now answer the following questions:
(i) List any two alternatives that Anita must have suggested to her grandmother.
(ii) How will Anita’s grandmother benefit herself and the community by not burning the firewood? Give one reason each. (2015)
Answer:
(i) Two alternatives suggested by Anita:

1. Use of biogas
2. Use of charcoal

(ii) Disadvantages of burning firewood:

1. Burning of firewood causes lots of smoke which harms the person who is cooking the food and causes air pollution which is harmful for the environment and harms the society as a whole.
2. Firewood leaves lots of ashes after burning so it pollutes the air we breathe thus making the atmosphere unclean.

Question 9.
State the principle of working of ocean thermal conversion plant. Explain how the plant works? Write one essential condition for it to operate properly. (2015)
Answer:
The energy available due to the difference in the temperature of water at the surface of the ocean and at deeper levels is called Ocean Thermal Energy (OTE).

Condition for it to operate properly:
Ocean thermal energy plants can operate if the temperature difference between the water at the surface and water at depths upto 2 km is 293 K (20°C) or more.

Working: The devices used to harness ocean thermal energy are called ocean thermal energy conversion power plants (or OTEC power plants). A temperature difference of 20°C (or more) between the surface water of ocean and deeper water is needed for operating OTEC power plants. In one type of OTEC power plant, the warm surface water of ocean is used to boil a volatile liquid like ammonia or a CFC.

The high pressure vapours of the liquid are then used to turn the turbine of a generator and produce electricity. The colder water from the deeper ocean is pumped up to cool the used up vapours and convert them again into a liquid. This process is repeated again and again.

Question 10.
(a) Water is an elixir of life, a very important natural resource. Your Science teacher wants you to prepare a plan for a formative assessment activity, “How to save water, the vital natural resource”. Write any two ways that you will suggest to bring awareness in your neighbourhood, on ‘how to save water’. (2017 OD)
(b) Name and explain any one way by which the underground water table does not go down further.
Answer:
(a) Ways to bring about awareness on ‘how to save’ water:

• We can conduct door to door campaign to make people aware about the acute shortage/ scarcity of water during summer.
• We can educate people on ways to save water, for example, close taps properly, use buckets of water to bathe instead of showers etc.
• I can also suggest them how to store rainwater in the small park of our locality, so that it can be used during hot summer days, when availability of water is very less.

(b) We can prevent the level of underground water table to not go down further by harvesting the rain¬water in the underground tanks in parks and cropfields.

Sources of Energy Class 10 Important Questions Long Answer Type

Question 1.
(a) Explain geothermal energy. How can it be harnessed to produce electrical energy?
(b) What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption? (2012)
Answer:
(a) Heat energy from molten rocks present inside the earth created under certain favourable conditions by natural processes is called geothermal energy.

• The deeper hot regions of earth’s crust are pushed upward and trapped in certain regions called ‘hot spots’.
• When underground water comes in contact with the hot spot, steam is generated.
• The steam trapped in rocks is routed through a pipe to a turbine and used to generate electricity. The cost of production would not be much but availability of such sites is very few.

(b) Environmental consequences of increasing demand for energy:

• Burning of fossil fuels produces acid rain which damages plants, soil and aquatic life.
• Fire wood causes soil erosion, destroys wild life and disturbs balance in nature.
• Nuclear power plants are increasing radioactivity in the environment.
• Construction of dams on rivers is destroying large ecosystems which get submerged under
  water in dams.

(ii) Steps to reduce energy consumption:

• Switching off electrical appliances when these are not in use.
• Using fuel saving devices such as pressure cooker, solar cooker, CFLs etc.
• Reduce the use of petrol by walking or cycling for short distances.
• Sending discarded items of paper, plastic, glass and metals for recycling to respective industries.
• Use of biogas as a fuel should be encouraged in rural areas.

Question 2.
(a) Explain what is geothermal energy?
(b) Write its one advantage and one limitation.
(c) Define (OTE).
(d) Write one advantage of nuclear fission reaction. (2012)
Answer:
(a) The heat energy from hot rocks present inside the earth is called geothermal energy. This heat can be used as a source of energy to produce electricity. Geothermal energy’ is one of the few sources of energy that does not come directly or indirectly from solar energy. At some places in the world, the rocks at some depth below the surface of the earth are very-very hot. This heat comes from the fission of radioactive materials which are naturally present in these rocks. Such places are called ‘hot spots’. These hot rocks heat the underground water and turn it into steam.

(b) Advantage: One advantage of using geothermal energy is that it does not cause any pollution so it is a clean and environment friendly source of energy.

Limitation: One disadvantage of geothermal energy is that it is not available everywhere. There are very limited number of places where geothermal energy can be harnessed on a commercial scale.

(c) The energy available due to difference in the temperature of water at the surface of the ocean and at deeper levels is called Ocean Thermal Energy (OTE).
Ocean Thermal plants can operate if the temperature difference between the water at the surface and water at depth up to 2 km is 293 k (20°C) or more.

(d) Enormous amount of energy can be produced from nuclear fission which can be used to run turbines for the production of electricity.

Question 3.
(i) Recently when Government decided to set up a nuclear power plant in an area, NGOs and local people raised their voice against it. They demanded that the Government should assure safety measures before setting up such a plant and Government assured them of it.
List any two concerns of the people for which they were demanding safety measures.
(ii) Determine the value of Atomic mass unit in terms of energy. (2013)
Answer:
(i) Two concerns of the people for which they were demanding safety measures:
(a) The major hazard of nuclear power plant is the storage and disposal of spent or used nuclear fuel. These wastes are radioactive in nature and emit harmful nuclear radiations. Improper storage or disposal of nuclear waste can pollute the environment.

(b) There is the risk of accidents in nuclear reactors. Such accidents lead to the leakage of radioactive materials, that can cause serious damage to plants, animals, human beings and the environment.

(ii) According to Einstein’s equation,
E = mc²
m = 1u (atomic mass unit) = 1.66 × 10^-27 kg
c = 2.998 × 10⁸ m/s
∴ E = 1.66 × 10^-27 × (2.998 × 10⁸)² Joules ⇒ E = 1.492 × 10^-10 J
∵ 1.602 × 10^-13 J = 1 MeV ⇒ 1.492 × 10^-10 J = 931 MeV
∴ 1u = 931 Me V

Question 4.
(a) Explain how geothermal energy is harnessed to produce electricity? (2013, 2015)
(b) Why is energy of flowing water in a river considered to be an indirect form of solar energy?
Answer:
(a) At some places in the world, the rocks at some depth below the surface of the earth are very-very hot.
This heat comes from the fission of radioactive materials which are naturally present in these rocks. The places where very hot rocks occur at some depth below the surface of the earth are called ‘hot spots’.

The extremely hot rocks present below the surface of the earth heat the underground water and turn it into steam. As more and more steam is formed between the rocks it gets compressed to high pressures. A hole is drilled into the earth up to the hot rocks and a pipe is put into it. The steam present around the hot rocks comes up through the pipe at high pressure. This high pressure steam turns the turbine of a generator to produce electricity.

(b) Solar energy evaporates the water from water bodies. These water vapours have potential energy in the form of clouds which is obtained from solar energy during evaporation. When clouds fall as rain and snow, potential energy changes into kinetic energy. Some of this rain water flows into the rivers. Thus kinetic energy of river water can be considered as an indirect form of solar energy.

Question 5.
Give the construction, working, advantages and disadvantages of a solar cooker. (2017 D)
Answer:
Solar Cooker is a device used to trap solar energy and utilize it to cook food. It consists of a box painted black from inside to absorb heat of the Sun (black colour is the best absorber of heat). A thick glass lid is placed over the box to trap heat energy of the Sun. A plane mirror reflector is also attached to the box so that a strong beam of sunlight falls over the cooker’s top.

The reflector of the solar cooker sends strong beams of sunlight over the top of the cooker. Sunlight consists of about l/3rd of infra-red rays which have a heating effect. These infra-red rays are of shorter wavelength as these are produced by a very hot source of heat. The glass lid over the cooker allows these infra-red rays of short wavelength into the cooker but does not allow the infra-red rays which are emitted by the black surface of the cooker to escape as these are of longer wavelength. Thus, heat energy of the Sun gets trapped in the black box of the solar cooker. This heat cooks the food material kept in the black box.

Advantages of solar cooker:

• It is used to cook food and saves precious fossil fuel.
• It does not cause any pollution.
• No smoke is produced during the working of a solar cooker.
• Nutrients of food material, which is to be cooked in the solar cooker, do not get destroyed.
• Four food items can be cooked at the same time.

Disadvantages of solar cooker:

• It cannot be used to cook food during the night.
• It cannot be used to cook food on a cloudy day.
• The direction of the reflector has to be changed after a small interval of time with the change of position of the Sun.

Question 6.
(a) Explain solar cell panel.
(b) Give the principle of working of a windmill. (2017 OD)
Answer:
(a) A solar cell is a device which converts solar energy directly into electricity. A group of solar cells is called a solar cell panel. It consists of a large number of solar cells joined together in a definite pattern. It provides a lot of electric energy required by artificial satellites, water pumps, street lighting, etc. For joining the various solar cells in a solar panel, silver wires are used because silver (metal) is the best conductor of electricity having a very low resistance, which also increases the efficiency.

(b) When the blowing wind strikes the blades of a windmill, it exerts a force on them. As a result of this force, the blades of the windmill start rotating. The rotation of the blades of the windmill causes to and fro (or up and down) motion in the crank (or connecting rod). This rotary motion is used to turn the turbines of electric generators to produce electricity and also to drive a large number of machines like water pumps and flour mills.
A large number of windmills erected over a large area are known as a wind energy farm.