A abampere (aA) The unit of electric current in the CGSeniu system, defined as that current that, if flowing through two parallel conductors of negligible cross section and infinite length, placed 1 cm apart in vacuo, would produce on each conductor a force of 1 dyne per centimeter of length. 1 abampere = 1 abcoulomb/s = r statampere (where c = speed of light in cm/s) = 10 ampere. aberration Imperfect image formation due to geometric imperfections in the optical elements of a system ablation 1 . The wasting of glacier ice by any process (calving, melting, evaporation, etc.). 2. The shedding of molten material from the outer sur- face of a meteorite or tektite during its flight through the atmosphere. absolute age The age of a natural substance, of a fossil or living organism, or of an artifact, obtained by means of an absolute dating method. See absolute dating method. absolute density Density in kg/m' or, more commonly, in g/cm\ both at STP. Cf. density, relative density abso
Source of Energy class 10 ncert physics MCQ & SAQ
Source of Energy class 10 ncert physics NCERT SOLUTION:
1. What is a good source of energy?
A good source of energy fulfills the following criteria:
→ It produces a lot of heat per unit mass.
→ It does a huge amount of work per unit mass.
→ It is easily accessible.
→ It is easy to store and transport.
→ It is economical.
→ It produces less smoke.
2. What is a good fuel?
A good fuel produces a huge amount of heat on burning, does not produce a lot of smoke, and is easily available.
3. If you could use any source of energy for heating your food, which one would you use and why?
Natural gas can be used for heating and cooking food because it is a clean source of energy. It does not produce a 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
1. What are the disadvantages of fossil fuels?
The disadvantages of fossil fuels are:
→ Burning of coal and petroleum produces a lot of pollutants causing air pollution.
→ Fossil fuels release oxides of carbon, nitrogen, sulfur, etc. that cause acid rain, which affects the soil fertility and potable water.
→ Burning of fossil fuels produces gasses such as carbon dioxide that cause global warming.
2. Why are we looking at alternate sources of energy?
Fossil fuels which are traditionally used by human beings everywhere as an energy source 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 energy sources. Hence, we should look for alternate sources of energy.
3. How has the traditional use of wind and water energy been modified for our convenience?
Earlier, the windmills were used to harness wind energy to do mechanical work such as lifting/drawing water from a well. Today, windmills are used to generate electricity.In windmills, the kinetic energy of wind is harnessed and converted into electricity.
Water energy which was used for transportation before is now a good source to generate electricity. Dams have been constructed on rivers for generating electricity. Waterfalls were used as a source of potential energy which was converted to electricity with the help of turbines.
Page No: 253
1. What kind of mirror - concave, convex or plain - would be best suited for use in a solar cooker? Why?
A concave mirror is used in a solar cooker as it uses the heat of the sunlight to cook food. 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 point.
2. What are the limitations of the energy that can be obtained from the oceans?
The forms of energy that can be obtained from the ocean are tidal energy, wave energy, and ocean thermal energy. There are several limitations in order to harness these energies.
→ Tidal energy depends on the relative positioning of the Earth, moon, and the Sun.
→ High dams are required to be built to convert tidal energy into electricity.
→ Very strong waves are required to obtain electricity from wave energy.
→ To harness ocean thermal energy efficiently, the difference in the temperature of surface water (hot) and the water at depth (cold) must be 20ºC or more.
3. What is geothermal energy?
Geothermal power plants use heat from the Earth to generate electricity. This heat energy of the Earth is known as geothermal energy.
4. What are the advantages of nuclear energy?
The advantages of nuclear energy are:
→ 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 one atom of carbon.
→ Fusion of four hydrogen atoms produces a huge amount of energy approximately equal to 27 MeV.
1. Can any source of energy be pollution-free? Why or why not?
No source of energy can be pollution-free. Every source of energy has some type of pollution. For example, the wastes of nuclear reactions are very dangerous to the environment.
2. Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?
Hydrogen gas is cleaner than CNG. CNG contains hydrocarbons. Therefore, it has carbon contents. Carbon is a form of pollutant present in CNG. On the other hand, hydrogen is waste-free. The fusion of hydrogen does not produce any waste. Hence, hydrogen is cleaner than CNG.
Page No: 254
1. Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Two renewable sources of energy are :
→ 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 of years more to burn. Therefore solar energy is a renewable source of energy.
→ 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.
2. Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
Answer
Two exhaustible energy sources are as follows:
→ Coal: It is produced from dead remains of plants and animals that remain buried under the earth's crust for millions of years. It takes millions of years to produce coal. Industrialization has increased the demand for coal. However, coal cannot replenish within a short period of time. Hence, it is a nonrenewable or exhaustible source of energy.
→ Wood: It is obtained from forests. Deforestation at a faster rate has caused a reduction in the number of forests on the Earth. It takes hundreds of years to grow a forest. If deforestation is continued at this rate, then there would be no wood left on the Earth. Hence, wood is an exhaustible source of energy.
Exercise
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
► (b) a cloudy day
Page No: 255
2. Which of the following is not an example of a biomass energy source?
(a) wood
(b) gobar gas
(c) nuclear energy
(d) coal
► (c) nuclear energy
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
► (c) Nuclear energy
4. Compare and contrast fossil fuels and the Sun as direct sources of energy.
Answer
Fossil fuels are energy sources, such as coal and petroleum, obtained from underneath the Earth's crust. They are directly available to human beings for use. Hence, fossil fuels are the direct source of energy. These are limited in amount. These are non-renewable sources of energy because these cannot be replenished in nature. Fossil fuels take millions of years for their formation. If the present fossil fuel of the Earth gets exhausted, its formation will take several years. Fossil fuels are also very costly.
On the other hand, solar energy is a renewable and direct source of energy. The Sun has been shining for several years and will do so for the next five billion years. Solar energy is available free of cost to all in an unlimited amount. It replenishes in the Sun itself.
5. Compare and contrast biomass and hydroelectricity as sources of energy.
Answer
Biomass and hydro-electricity both are renewable sources of energy. Biomass is derived from dead plants and animal wastes. Hence, it is naturally replenished. It is the result of natural processes. Wood, gobar gas, etc. are some of the examples of biomass.
Hydro-electricity, on the other hand, is obtained from the potential energy stored in water at a height. Energy from it can be produced again and again. It is harnessed from water and obtained from mechanical processes.
6. What are the limitations of extracting energy from -
(a) the wind? (b) waves? (c) tides?
Answer
(a) A windmill requires wind of speed more than 15 km/h to generate electricity from wind energy. Also large numbers of windmills are required to get feasible output which covers a large area.
(b) Very strong ocean waves are required in order to extract energy from waves.
(c) Very high tides are required in order to extract energy from tides. Also, occurrence of tides depends on the relative positions of the Sun, moon, and the Earth.
7. 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 a renewable source of energy. Sun, wind, moving water, biomass, etc. are some of the examples of renewable sources of energy.
The source of energy that does not replenish in nature is known as a 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. Biomass is one of the inexhaustible sources of energy.
Yes. The options given in (a) and (b) are the same.
8. What are the qualities of an ideal source of energy?
Answer
An ideal source of energy must be:
→ Economical
→ Easily accessible
→ Smoke/pollution free
→ Easy to store and transport
→ Able to produce huge amount of heat and energy on burning
9. What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?
Solar cookers use the Sun's energy to heat and cook food. It is an inexhaustible and clean renewable source of energy. It is free for all and available in unlimited amounts. 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 days, it becomes useless.
The places where the days are too short or places with cloud covers round the year, have limited utility for solar cookers.
10. What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Answer
Industrialization increases the demand for energy. Fossil fuels are easily accessible sources of energy that fulfill this demand. The increased use of fossil fuels has a harsh effect on the environment. Too much exploitation of fossil fuels increases the level of greenhouse gas content in the atmosphere, resulting in global warming and a rise in the sea level.
It is not possible to completely reduce the consumption of fossil fuels. However, some measures can be taken such as using electrical appliances wisely and not wasting electricity. Unnecessary usage of water should be avoided. Public transport systems with mass transit must be adopted on a large scale. These small steps may help in reducing the consumption of natural resources and conserving them.
Source of Energy class 10 ncert physics MCQ
1. Radiations which are harmful to the living organisms are
(a) Infrared radiation.
(b) ultraviolet radiations
(c) Visible radiation.
(d) microwaves
► (b) ultraviolet radiations
2. Which of the following problems is associated with the burning of coal?
(а) Carbon-dioxide emission
(b) acid rain
(c) ash with toxic metal supurity
(d) All of the above
► (d) All of the above
3. An ideal source of energy should have
(a) higher calorific value
(b) easy transportability
(c) easy accessibility
(d) All the above
► (d) All the above
4. A solar cooker may not cook food if.
(a) Interior of the box and the container of food are perfectly shining.
(b) Glass sheet over the box is not closed.
(c) Solar cooker is placed in the shade.
(d) All the above
► (d) All the above
5. What are the disadvantage of solar energy
(a) A large surface area is required collect the solar
(b) Daily average of solar energy varies from 4 to 7 kwh/m2
(c) Highly hazardous toxic material is used in the manufacturing of solar devices.
(d) All of the above
► (d) All of the above
6. Solar cells are made of
(a) metals
(b) insulator
(c) semiconductors
(d) None of these
► (a) Seine conductors
7. Solar cells are made of
(a) germanium
(b) silicon
(c) silver
(d) aluminum
► (b) silicon
8. The use of reflector in the solar cooker is to
(a) Decrease efficiency
(b) create greenhouse effect
(c) increase efficiency
(d) None of the above
► (c) increase efficiency
9. Wind is caused due to
(a) uneven heating of earth’s surface
(b) rotation of earth
(c) local conditions
(d) All of the above
► (d) All of the above
10. Hydropower plant are located in the
(a) desert area
(b) plane area
(c) hilly terrains
(d) None of the above
► (c) hilly terrains
11. Select the important factor for the site selection of a thermal power plant.
(a) Distance from the populated area
(b) Availability of fuel
(c) Availability of water
(d) Cost of plant
► (c) Availability of water
12. The main constituent of CNG is
(a) butane
(b) methane
(c) ethane
(d) propane
► (b) methane
13. The temperature inside the solar cooker ranges from
(a) 500-100°C
(b) 100-140°C
(c) 150-200°C
(d) 70-80°C
► (b) 100-140°C
14. Which of the following is not a biomass energy source?
(a) gobar gas
(b) coal
(c) wood
(d) nuclear energy
► (d) nuclear energy
15. Energy can neither be created nor destroyed but still everybody discuss about the energy crisis because
(a) Energy transforms into different forms continuously.
(b) Usable forms of energy are dissipated to the surroundings in less usable forms.
(c) Energy is consumed and cannot be used again.
(d) All of the above
► (d) All of the above
16. Dead organisms are transformed into petroleum and natural gas in
(a) presence of air
(b) absence of air
(c) presence of sunlight
(d) none of the above
► (b) absence of air
17. Which of the following organisms produces biogas from cow drug sherry in the biogas plant?
(a) aerobic bacteria
(b) anaerobic bacteria
(c) protozoa
(d) fungi
► (b) anaerobic bacteria
18. The variety of coal which has the highest car-bon content
(a) Anthracite
(b) Peat
(c) Bituminous
(d) Lignite
► (a) Anthracite
19. U-235 will undergo fission by
(a) low energy neutrons only
(b) high energy neutrons only
(c) medium energy neutrons
(d) low energy protons only
► (d) low energy protons only
20. Tidal energy is harnessed by constructing a dam across
(a) narrow opening to the sea
(b) wide opening to the sea
(c) the river in hilly trains
(d) the river in plane areas
► (a) narrow opening to the sea
21. Which of the following is more environmentally friendly?
(a) Burning of coal
(b) burning of firewood
(c) burning of charcoal
(d) Burning of diesel.
► (c) burning of charcoal
22. Geothermal energy is
(a) Heat energy in the interior of earth
(b) energy of molten mars exists in the farm of magma inside the earth.
(c) molten lava on the surface of earth
(d) energy obtained from solar thermal electric plants
► (c) molten lava on the surface of earth
23. Major problem in harnessing nuclear energy is to
(a) split heavy nucleus
(b) sustain nuclear reactions
(c) Convert nuclear energy into electricity
(d) dispose of spent fuel safely.
► (d) dispose of spent fuel safely.
24. A good fuel should possess
(a) high ignition temperature
(b) moderate ignition temperature
(c) high calorific value
(d) both high calorific value and moderate ignition temperature
► (d) both high calorific value and moderate ignition temperature
25. Which of the following is the ultimate source of energy?
(a) Water
(b) Sun
(c) Fossil fuels
(d) Uranium
► (b) Sun
26. Fusion reaction is also known as
(a) chemical reaction
(b) elastic scattering
(c) thermonuclear reaction
(d) photo nuclear reaction
► (c) thermonuclear reaction
27. Which of the following gasses is the main con-stituent of natural gas?
(a) Methane
(b) Ethane
(c) Propane
(d) Butane
► (a) Methane
28. India exploded her first underground nuclear device at
(a) Ranchi
(b) Kota
(c) Jaipur
(d) Pokhran
► (d) Pokhran
29. 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
► (b) a cloudy day
30. A device in which electricity is produced by the process of controlled nuclear fission reaction is called
(a) nuclear chain reaction
(b) hydel power plant
(c) nuclear reactor
(d) thermal power plant
► (c) nuclear reactor
31. Which of the following is not an example of biomass energy?
(a) wood
(b) gobar-gas
(c) nuclear energy
(d) coal
► (c) nuclear energy
32. Ocean thermal energy is produced due to
(a) Pressure difference at different levels in the ocean.
(b) temperature difference at different levels in the ocean.
(c) energy stored by waves in the ocean.
(d) tides rising out of the ocean.
► (b) temperature difference at different levels in the ocean.
33. One major problem in harnessing nuclear energy is
(a) converting nuclear energy into electrical energy.
(b) sustaining the reaction.
(e) splitting the nuclei.
(d) disposing of spent fuel easily.
► (d) disposing of spent fuel easily.
34. The working fluid in ocean thermal power plant is
(a) Volatile liquid like ammonia
(b) petrol
(c) charcoal
(d) liquified petroleum gas
► (a) Volatile liquid like ammonia
35. Tidal energy is a farm of energy obtained from the
(a) motion of surface water in ponds
(b) ocean in the form of tidal waves
(c) tides occurs in the river water
(d) motion of the wave in sea
► (b) ocean in the form of tidal waves
36. 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
► (c) nuclear energy
37. A solar panel is made by combining in an arrangement
(a) solar concentrator
(b) solar cookers
(c) solar cells
(d) solar chimney
► (c) solar cells
38. Biogas is a better fuel than animal dung cake because
(a) biogas has lower calorific value.
(b) animal dung cake has high calorific value
(c) biogas bums smoke and leaves no residue
(d) biogas is used as a fuel for cooking only whereas dung cake can be used for cooking, illuminating the lanterns.
► (c) biogas bums smoke and leaves no residue
39. The material used for interconnection the solar cells in the solar panel is
(a) silicon
(b) silver
(c) aluminum
(d) copper
► (b) silver
40. Biogas is formed in the
(a) presence of air only
(b) presence of water only
(c) absence of air only
(d) presence of water and absence of air
► (d) presence of water and absence of air
41. Unit of calorific value of a substance is
(a) Kcal
(b) Joules
(c) J kg
(d) J/kg
► (d) J/kg
Source of Energy class 10 ncert physics SAQ
1.Name any two fossil fuels.
Ans. A good fuel is the one which
has high calorific value,
is non-polluting,
is easy to transport and easily available,
has moderate ignition temperature.
.Mention the purpose of blackening the interior of a solar cooker.
Answer. The purpose of blackening the interior of a solar cooker is that the black surface absorbs more heat radiations of incident solar energy (about 98%) as compare to white or other light coloured surface
3.Why do people oppose the construction of Tehri Dam on the river Ganga and Sardar sarovar project on the river Narmada. (Or)
Mention three disadvantage of producing hydroelectricity by constructing the dams.(Or)
List any three ways in which construction of dams for production of electricity adversely affects the environment of that place.
Answer.
Large area is required to build the dam that results in rehabilitation of displaced people.
Large ecosystems are destroyed when submerged under the water in dams.
The vegetation which is submerged rots under anaerobic conditions and gives rise to large amounts of methane gas which leads to a green-house effect.
Explain how the tidal energy is harnessed and write one limitation of the use of tidal energy.
Answer.
(a) Tidal energy: The energy produced by the surge of ocean water during high and low tides due to difference in sea-levels is called tidal energy. The high and low tides occur due to the gravitational pull of the moon. This causes enormous movement of water.
(b) Tidal energy is harnessed by constructing a dam near the shores. During the high tides water flows into the dam and during the low tides, water flows out. This flowing water rotates the turbine, present at the opening of the dam and produces electricity.
7. Define the process of nuclear fission. Write the steps involved in generating electricity in a nuclear reactor.
Answer. Nuclear Fission: The process in which a heavy nucleus (such as uranium, plutonium or thorium) is broken into two nearly equal fragments when bombarded with low-energy neutrons and a tremendous amount of energy is released. This process is called nuclear fission.
Steps involved in generating electricity:
The fuel rods full of uranium pellets are placed in a nuclear reactor chamber.
Low-energy neutrons are bombarded on uranium fuel rods.
A self-sustaining fission chain reaction starts that releases energy at a controlled rate.
With this heat the reactor converts water to steam at a high temperature and pressure.
This high temperature and pressure steam spins generator turbines producing electricity.
The steam cools back into water, which can then be used over again.
9.Solar cooker takes more time as compared to the LPG to boil potato or rice, yet Kunal uses solar cooker for such type of cooking:
(i) Why does Kunal use a Solar cooker instead of LPG? Give reasons for your answer.
(ii) Name the phenomenon which is responsible for obtaining high temperatures in solar cookers.
Answer.
(a)(i) There are no energy losses while cooking on the solar cooker as the food gets cooked in a controlled environment whereas cooking on the LPG leads to a maximum percentage of energy loss.
(ii) Temperature controlled cooking retains the nutrient value of the food.
(iii) Using the solar cooker, LPG can be served which results in reduction in the emission of CO2.
(iv) It saves a lot of time which is normally consumed for cooking purposes.
(b) Greenhouse effect.
10. Manoj’s father works in a nuclear power reactor. He asked his father to take him for a visit to the nuclear power reactor. But his father was not keen to take him there. Now answer the following questions:
(i) What could be the possible reason for Manoj's father not taking him to the nuclear power reactor?
(ii) Write one advantage and one disadvantage of setting up a nuclear power reactor. .
Answer.
(a) (i) Safety concerns.
(ii) Health concerns.
(b) Advantage: From a small amount of nuclear fuel, a large amount of energy is released in a nuclear power reactor.
Disadvantage: There is risk of harmful radiation leakage from nuclear waste.
Q1. Name any two elements that are used in fabricating solar cells. [CBSE 2019]
Silicon and gallium.
Q2. What are solar cells? Explain the structure of the solar panel. List two principal advantages associated with solar cells. [CBSE 2019]
Top Courses for Class 10A solar cell is a device that converts solar energy directly into electricity.
Construction: The box of the solar cooker is made of non-conducting material e.g., plastic or fiberglass with thick inner walls. These walls are painted in black. A plane mirror is hinged on the top so that it reflects sunlight into the box.
Working: The purpose of the box is to increase the effective area for the collection of solar energy.
The whole box is covered with glass sheets. These glass sheets prevent the loss of longer
wavelength infrared radiation from inside the box to outside.
Within two to three hours, the temperature inside rises to about 140 °C.
Solar Cooker
Q3. ‘Bio-gas is an excellent fuel’. List four reasons to justify this statement.
Write the main constituent of this gas and state its percentage. [CBSE 2019]
The four gasses commonly present in bio-gas are methane, carbon dioxide, hydrogen and hydrogen sulfide.
Main advantages of using biogas over fossil fuels are as given below :
Biogas is an excellent fuel as it contains up to 75% methane which burns without smoke.
Bio-gas bums completely and leaves no residue i.e., ash.
Bio-gas is a renewable, convenient and efficient source of energy, whose heating capacity is high.
It gives us a safe method to dispose of wastes like animal dung, human excreta and other bio-wastes.
Q4. Name any two nutrients that the spent slurry has in a bio-gas plant. [CBSE 2019]
Nitrogen and phosphorus are two nutrients present in the spent slurry.
Q5. Why is biogas considered an excellent fuel? [CBSE 2019]
Bio-gas is an excellent fuel because it burns without smoke, leaves no residue ash and its heating capacity is high.
Q6. What is a dam? Why do we seek to build large dams? While building large dams, which three main problems should particularly be addressed to maintain peace among local people? Mention them. [CBSE 2018]
A dam is a huge construction being done to obstruct the river flow at the place. As a result, a large artificial lake is created there which can be used to store water.
We want to build large dams so as to store a large amount of water, which can then be used to produce electricity by means of a hydropower plant.
Dam
While building large dams, the following three main problems should particularly be addressed to maintain peace among local people:
Construction of the dam involves submergence of large areas of agricultural and forest land and human habitation.
Large ecosystems are destroyed.
Problem of satisfactory rehabilitation of displaced people is a major problem.
Q7. Write the energy conversion that takes place in a hydropower plant. [CBSE 2018]
The energy transformation taking place at hydropower plants is shown below:
Q8. Name two constituents of biogas. [CBSE 2018C]
Methane CH4, Hydrogen H2, carbon dioxide C02, hydrogen sulfide H2S.
Q9. What is biogas? Describe the steps involved in obtaining biogas. [CBSE Sample Paper 2018]
Biogas is a mixture of methane, carbon dioxide, hydrogen and hydrogen sulfide.
Following are the various steps involved in the biogas plant for obtaining biogas.
Q10. Write the percentage of methane in biogas. [CBSE 2016]
75% of bio-gas is methane.
Q11. Mention three ways to reduce the pollution caused by fossil fuels. [CBSE 2016]
Three possible ways to reduce the pollution caused by fossil fuels are :
Increase the efficiency of the combustion process.
Adequate techniques must be employed so as to reduce the escape of harmful gasses and ash into the surroundings.
Fossil fuel may be used to generate electricity, which can then be conveniently used in homes and industry.
18 State any three reasons to justify that LPG is considered as an ideal fuel.
Answer. LPG is considered as an ideal fuel because
It is easy to store, handle and transport.
It produces a large amount of heat on burning.
It does not leave any residue on burning,
19 State any three advantages of charcoal over wood.
Answer. Advantages of charcoal over wood
It has higher calorific value, i.e. higher heat generating efficiency.
Charcoal does not produce smoke on burning so it is a clean fuel.
It is easier to transport and ready to use in a convenient dry and broken-up form.
20. Ramesh is a student of standard X. He organized many activities in his school to convey to the students about the various advantages and disadvantages of using renewable and non-renewable sources of energy. Many students of the school took part and concluded about the best choices of energy sources on this basis.
Answer the following questions:
(i) What activities Ramesh might have had assigned for the students?
(ii) Name any two renewable sources of energy.
(in) Which two values are reflected in Ramesh’s thought and action?
(i) Activities that Ramesh have had assigned for the students are:
(a) Hands on projects related to renewable and non-renewable sources of energy.
(b) Photograph exhibitions on the topic “use of fossil fuel and its impact on the environment.”
(c) Essay writing competition on a “renewable energy technology that could potentially be used for community.”
(d) Group discussion on advantages and disadvantages of using renewable and non-renewable sources of energy for selection of the best source of energy.
(ii) Solar energy, hydro energy.
(iii) Ramesh’s thought: Higher degree of general awareness of proper use of renewable sources of energy.
Ramesh’s action: Concern for community advantage and good management.
21. Megha asked her mother to install a solar water heater on the rooftop. Her mother asked about the need for such an installation. Megha convinced her mother and succeeded in setting up a solar water heater on her roof top.
(i) State one advantage of installing the solar water heater to Megha’s family and to the society.
(ii) What qualities of Megha are reflected in her actions?
(iii) State one limitation in using solar water heaters.
Answer.
(i) Advantage of solar water heater (any one)
(a) Once a solar water heater is installed, the family and society never need to pay for heating up the water again.
(b) Megha’s family and society make their contribution to the nation to curb the emission of greenhouse gasses.
(ii) General awareness, concern for community advantage and proper use of renewable source energy.
(iii) (a) It does not work at night as well as on cloudy days.
(b) Relatively low heating system efficiency of passive solar water.
22. Mariyam made a solar cooker on her own. She used a white metallic box with a lid. She put the food in the solar cooker for heating and closed the lid. But she did not get good results. She then consulted her teacher to know her mistakes. Her teacher pointed out her mistakes, which she later rectified.
(a) According to you, which two mistakes were made by Mariyam and what
What did she do to rectify them?
(b) Which qualities of Mariyam are rectified in her action.
answer.
(a) The possible mistakes were made by Mariyam are:
The outer and interior of the solar cooker might not have been blackened.
Instead of using a glass lid she might have used a plastic cover.
The solar cooker might not have been insulated properly.
The cooker utensil used for cooking might not have been blackened.
(b) • Gaining practical knowledge of what she has learned in theory. She wanted to adopt an eco-friendly lifestyle.
Bio gas is considered to be a boon to the farmers. Give reasons.
answer.
It is the source of excellent manure, rich in nitrogen and phosphorous which
can be obtained from the biogas plant in addition to biogas.It provides a safe, efficient and profitable disposal method for bio-waste and sewage material.
40. What are the advantages of nuclear energy?
answer. Advantages of nuclear energy are:
A small quantity of nuclear fuel is needed to produce a large amount of useful energy.
Nuclear power plants produce less atmospheric pollution than thermal power plants, if the nuclear fission reaction is performed properly.
Small amount of nuclear fuel can run a nuclear power plant over a long period of time. There is no need to insert the nuclear fuel in the nuclear reactor again and again in a short period as in the case of a thermal power plant.
41. What is a solar cell panel? Mention any three of its applications.
answer. A large number of solar cells combined in an arrangement to obtain large electrical power is called a solar cell panel.
Applications of solar cell panel are:
It provides the electric power for the:
working of artificial satellites stationed in outer space,
running of irrigation water pumps by the farmers in rural areas,
street lighting in remote areas.
42. Out of two solar cookers, one was covered with a plane glass slab and the other was left open. Which of the two solar cookers will be more efficient and why?
answer. The solar cooker which was covered with a plane glass slab would be more efficient. The glass lid allows the heat radiation from the sun to enter the solar cooker but does not allow the reflected heat radiation to escape or go outside the box. Thus, heat trapped inside the box increases the temperature. Glass lid also reduces heat loss due to reflection.
List any three hazards of nuclear waste. How does the disposal of nuclear waste pose a problem for plant and animal life?
answer. Hazards of nuclear wastes are:
Nuclear waste contains radioactive substances which emit harmful nuclear radiations.
There is a high risk of environmental contamination.
It is highly toxic.
Effect of nuclear waste on plant and animal life is:
The radiation emitted from the nuclear waste penetrates deep inside the human or animal body where they can damage biological cells thereby initiate cancer or cause genetic disease.
Increased mortality of plants, soil invertebrates and mammals and reproductive losses in plants and animals have also been observed.
44. (a) Charcoal is a better fuel than wood. Why? .
(b) How does a biogas plant help to reduce the problem of pollution?
answer.
(a) Charcoal is considered to be a better fuel than wood because:
It burns without flames.
It is comparatively smokeless.
It has higher calorific value, i.e. higher heat generating efficiency than wood.
(b) Biogas plants help to reduce the problem of pollution in the following ways.
It provides better sanitation due to safe disposal of bio-waste and sewage material.
Biogas obtained from this plant produces less smoke on burning. (Hi) The residue left can be used as a manure which can be used as an alternative
of fertilizers. Thus, it prevents soil and water from degradation.
Mention any four limitations in harnessing wind energy on a large scale.
answer. Limitations in harnessing wind energy are:
Speed of wind is not available at all times and at all places.
To establish the wind energy farm, a large area of land is needed.
Speed of wind should be higher than 15 km/h to harness the wind energy.
Construction of the windmill and its installation is very expensive.
48. What happens when wood is burnt in a limited supply of oxygen? Name the residue left behind after the reaction and state two advantages of using this residue as a fuel over wood.
answer. When wood is burnt in a limited supply of oxygen, volatile materials present in it get removed and cooled to get wood tar and wood gas.
The black residue left behind after the reaction is known as charcoal. Advantages of using charcoal as a fuel over wood are:
Burning of charcoal does not produce smoke. On the other hand, wood produces a lot of smoke on burning.
For a given quantity, charcoal produces more heat than wood.
49. Name four gasses commonly present in biogas. State two advantages of using this gas over fossil fuels.
answer. Methane, carbon dioxide, hydrogen and hydrogen sulfide.
Advantages of using biogas over fossil fuels are:
Biogas burns without smoke, leaving no residue unlike coal.
Biogas is cheaper as compared to fossil fuels.
50. How are the wastes produced in nuclear power plants different from those produced in thermal power plants ? What happens to the waste of a nuclear power plant?
answer.The waste obtained from nuclear power plants is highly radioactive in nature which emits harmful radiations, whereas waste produced in a thermal power plant is non-radioactive.
Management of nuclear waste is given as follows:
Some products of nuclear waste are buried in sealed steel/lead containers for long term storage, buried under the ground or dumped in vacated coal mines.
Other waste product
In a solar cooker, the following arrangements are made. Write one function of each arrangement.
(a) The box is made of insulating material such as plastic or wood.
(b) The inner walls of the box are painted black.
(c) The box is covered with a transparent glass sheet.
(d) A plane mirror is hinged at an angle at the top of the box.
answer.
(a) To avoid loss of heat from the solar cooker to the surroundings.
(b) Black surface absorbs more heat radiations of incident energy.
(c) Transparent glass sheet does not allow the reflected heat radiation to go outside the box.
(d) To increase the amount of solar energy incident on the transparent glass sheet.
52. Describe how hydro energy can be converted into electrical energy. Write any
two limitations of hydro energy.
answer. Conversion of hydro energy into electrical energy
High rise dams are constructed on the river to obstruct the flow of water to collect it at a suitable height. The stored water has a lot of potential energy.
The water from a suitable height is allowed to fall on the blades of a turbine located at the bottom of a dam through a pipe.
Kinetic energy of flowing water rotates the turbine rapidly. Rotation of the turbine helps the armature coil of the generator to rotate rapidly in the magnetic field. Thus, hydroelectricity is generated.
Limitations of hydro energy:
(i) All river-sites are not suitable for construction of dams.
(ii) Large ecosystems are destroyed when submerged under the water in dam
Q12. Explain the term ‘tidal energy’. How is electricity produced from tidal energy? [CBSE 2016]
Tidal energy is the kinetic energy possessed by the rising and falling water in seas and oceans during high and low tides respectively. To harness tidal energy, a dam is constructed across a narrow opening to the sea. The water moves in and out of the openings in the dam during high and low tides. As the water moves through the openings, it flows over the turbines fixed inside the dam that generates electricity.
Tidal Energy
Q13. (i) Name the four gasses commonly present in biogas.
(ii) List two advantages of using biogas over fossil fuels. [CBSE 2016]
(i) The four gasses commonly present in bio-gas are methane, carbon dioxide, hydrogen and hydrogen sulfide.
(ii) Main advantages of using biogas over fossil fuels are as given below :
Biogas is an excellent fuel as it contains upto 75% methane which burns without smoke.
Biogas bums completely and leaves no residue i.e., ash.
Biogas is a renewable, convenient and efficient source of energy, whose heating capacity is high.
It gives us a safe method to dispose of wastes like animal dung, human excreta and other bio-wastes.
Q14. Define the process of nuclear fission. Write the steps involved in generating electricity in a nuclear reactor.
OR
Define nuclear fission. Write the steps involved in generating electricity in a nuclear reactor. [CBSE 2016]
Nuclear Fission: The process in which a heavy nucleus (such as uranium, plutonium or thorium) is broken into two nearly equal fragments when bombarded with low-energy neutrons and a tremendous amount of energy is released. This process is called nuclear fission.
Steps involved in generating electricity:
Fuel rods full of uranium pellets are placed in a nuclear reactor chamber.
Low-energy neutrons are bombarded on uranium fuel rods.
A self-sustaining fission chain reaction starts that releases energy at a controlled rate
With this heat, the reactor converts water to steam at a high temperature and pressure
This high temperature and pressure steam spin the generator turbines producing electricity.
The steam cools back into water, which can then be used over again.
Q15. Identify the part of a solar cooker that produces a greenhouse effect. [CBSE 2016]
The plane glass plate cover of a solar cooker produces a greenhouse effect.
Q16. What is the minimum wind velocity required for obtaining electric power with a windmill generator? [CBSE 2016]
15 km h-1.
Q17. Name any two nuclear fuels used for the process of nuclear fission. [CBSE 2016]
Uranium and plutonium.
Q18. (a) How is charcoal a better fuel than wood? Why? [CBSE 2016]
(b) How does a bio-gas plant help to reduce the problem of pollution?
(a) Charcoal is a better fuel than wood because it burns without flames, is comparatively smokeless and has a higher heat generation efficiency.
Charcoal
(b) A bio-gas plant helps to reduce the problem of pollution by utilizing waste biomass by producing biogas and manure.
Q19. (a) List in tabular form two major differences between renewable and nonrenewable sources of energy.
(b) Why are fossil fuels classified as non-renewable sources of energy? [CBSE 2016]
(a)
(b) Fossil fuels were formed due to certain very slow changes occurring inside the earth under special circumstances spread over millions of years. Since these conditions are not prevailing now, it is not possible to replenish the amount of fossil fuels being consumed. Hence, these are classified as non-renewable sources of energy.
Q20. State any three limitations of harnessing nuclear energy. [CBSE 2016]
Three main limitations of harnessing nuclear energy are as follows :
The most important problem is the storage and disposal of spent or used fuel because it is highly radioactive. Improper nuclear waste storage and disposal may lead to environmental contamination.
There is a risk of accidental leakage of nuclear radiation from the nuclear reactor.
The cost of installation of a nuclear power plant is very high.
Q21. How is nuclear energy generated? State in brief the process of utilizing this energy in the production of electricity. Mention the major hazard of nuclear power generation. [CBSE 2016]
Nuclear energy is generated by the process of nuclear fission. The nucleus of a heavy atom such as uranium or plutonium, when bombarded with low energy neutrons, can be split apart into two lighter nuclei along with the release of a tremendous amount of energy.
We design a nuclear reactor in which the process of nuclear fission takes place at a sustained rate and energy is released at a uniform rate. This energy is utilized to convert water into steam, which then does work for rotating the turbine of the electric generator. As a result, electricity is produced.
The major hazard of nuclear power generation is the storage and safe disposal of spent or used fuel so that no environmental contamination takes place.
Q22. Write one advantage of nuclear fission reaction. [CBSE 2015]
In a nuclear fission reaction a large amount of energy is released by a small quantity of nuclear fuel, which can be easily converted into electrical energy.
Q23. Mention the two factors that cause the wind to blow. [CBSE 2015]
Wind is caused by unequal heating of landmass and water bodies by solar radiation.
Q24. Define the process of "nuclear fission”. [CBSE 2015]
Splitting up of a nucleus of uranium, when bombarded by neutrons, into two lighter nuclei along with release of a large amount of energy is called nuclear fission.
Q25. Explain how a hydropower plant produces electricity. [CBSE 2015]
A hydropower plant converts the potential energy of stored water into electricity.
To produce hydropower electricity, a high rise dam is constructed at a suitable place on the river to obstruct the flow of water and thereby collect water in a large-sized reservoir. Due to the rise of the water level, the kinetic energy of flowing water is transformed into the potential energy of stored water.
The water from the high level in the dam is carried through sluice gates and pipes to the turbine of the electric generator, which is fitted at the bottom of the dam. Due to flowing water, the turbine is rotated at a fast rate and electricity is produced.
Q26. (a) Define tidal energy.
(b) Explain how tidal energy is harnessed and write one limitation of the use of tidal energy. [CBSE 2015]
(a) Tidal energy: The energy produced by the surge of ocean water during high and low tides due to difference in sea-levels is called tidal energy. The high and low tides occur due to the gravitational pull of the moon. This causes enormous movement of water.
(b) Tidal energy is harnessed by constructing a dam near the shores. During high tides water flows into the dam and during low tides, water flows out. This flowing water rotates the turbine, present at the opening of the dam and produces electricity.
Limitation of the use of tidal energy:
The power output is variable, intermittent and is not on a large scale.
There are very few suitable sites that too with high installation cost of plant and its maintenance cost.
Q27. How can one say that the Sun is the main source of energy on the earth? [CBSE 2015]
Solar energy manifests itself in many forms through many processes both biological and physical. Plants utilize solar energy for photosynthesis. The solar energy trapped by land and water bodies brings about many physical changes resulting in wind, storm, ocean waves etc. Also fossil fuels e.g., coal, natural gas, petrol etc., have been formed due to very slow changes which occurred millions of years ago and were related to solar energy.
The energy of bio-gas etc. is also derived from solar energy.
Source of Energy class 10 ncert physics long question
Q1. Burning of fossil fuels causes lots of air pollution. Generally these fossil fuels are used in our vehicles.
(i) As an aware citizen, list two ways to reduce air pollution caused due to vehicles.
(ii) Write two harmful effects other than air pollution that are caused due to burning of fossil fuels. [CBSE 2015]
(i) Two ways to reduce air pollution caused due to vehicles are as follows:
The petrol used should be free of lead and sulfur impurities because oxides of these elements are toxic and cause much air pollution.
Vehicles using diesel should be replaced by vehicles using CNG as fuel.
(ii) Two harmful effects, other than air pollution, caused due to burning of fossil fuels are as follows:
Burning of fossil fuels produces oxides of nitrogen and sulfur. These gasses are acidic in nature and lead to acid rain which adversely affects our water and soil resources.
Burning of fossil fuel produces carbon dioxide, which is a greenhouse gas and leads to global warming causing a lot of environmental and ecological problems.
. Reena’s father works with a company that builds dams. Once he took her to the site where a dam was being built. Reena saw a group of people sitting there shouting slogans against the building of the dam. She talked to the group of people and asked them about their problems and then discussed it with her father. She then tried to convince the people to talk with the authorities and come to an amicable solution. The discussion was successful. Reena’s father was very proud of his daughter. Now answer the following questions:
(i) Why was Reena’s father proud of his daughter?
(ii)Why was the group of people protesting against the building of the dam?
(iii) Reena’s contribution to the peaceful resolution of the conflict proved to be a boon for many citizens of the country. How?
Answer.
(i) Because she convinced the people by explaining to them the advantages of constructing dams and came up with a solution of rehabilitation of displaced peoples. So the contribution to the peaceful resolution of the conflict makes Reena’s father proud of his daughter.
(ii)The group of people protesting against the building of dam because of following disadvantages
(a) A large area of agricultural land and human habitation are sacrificed as it gets submerged at the dam site.
(b) Large ecosystems are destroyed when submerged under water.
(c) The decomposition of vegetation under anaerobic conditions produces methane gas which is also a greenhouse gas.
(iii)(a) The citizens are not affected by flood as it can be controlled by storing the water behind the dam.
(b) Farmers get benefited as water for irrigation is available for the whole year.
(c) Low cost of production of electricity gives monetary gain which is a boon to citizens
Bio gas is an excellent fuel. Justify the statement by giving two reasons. Mention the main constituents of bio gas along with its percentage.
Answer.
(i) It burns without smoke and leaves no residue therefore causes no atmospheric pollution.
(ii)Its heating capacity is high, i.e. it has a high calorific value. Main constituents of bio gas: The composition of bio gas varies depending upon the nature of organic matter feeding in the digester and advanced waste treatment technology. The typical composition of bio gas is
Methane 50 – 75%
Carbon dioxide 25 – 50%
Nitrogen 0 – 10%
Hydrogen 0 – 1%
Hydrogen sulfide 0 – 3%
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 neighborhood. There were plenty of livestocks and the household used cooking gas from the plant. Also their farms had rich vegetation. They contacted the sarpanch of the village and convinced him to set up a biogas plant for the village community.
(a) Mention the values displayed by Mr. Nair, Nikhil and Neha.
(b) Explain the possible arguments given by Nikhil and Neha to the sarpanch to convince him to set up a community biogas plant.
Answer.
(a) Mr Nair: Higher degree of general awareness, helping nature.
Nikhil and Neha: Knowledge sharing.
• helping nature.
• concern for community advantage.
(b) Possible arguments given by Nikhil and Neha in favor to set up community biogas plant, to the sarpanch on
Economical source of energy.
Cleanliness of the whole village.
Use of slurry left behind as mannar which is rich in nitrogen and phosphorus.
It reduces air pollution and greenhouse effect.
It raises the standard of living.
It is beneficial to entire village community. Basically they discuss and explain the advantages of community biogas plant for the entire village.
Aditya suggests his family install a solar water heater at their residence. But
Some of the family members were in favor of installing an electric geyser.
Ultimately the family got a water heater installed.
(a) Which according to you was correct? Give two reasons in support of your answer.
(b) Mention two possible changes in the thinking of the family members
because of the arguments Given by Aditya.
answer. (a) The decision of installing the solar water heater was correct this is due to
(i) Their system uses solar energy which is a renewable source of energy and free.
(ii)It will reduce our dependence on fossil fuel, improve our energy security and reduce the country's import bill for fuel.
(b) Two possible changes in the thinking of the family members because of the arguments given by Aditya are:
(i) We should conserve the non-renewable fuels for applications for which renewable sources of energy are not easily available.
(ii)Solar water heating is a good investment and cost effective. It is one of the safe and efficient ways to deliver hot water free of cost.
Traffic jams outside the school gate was a common sight since most of the students came in their own cars. This became a topic for discussion at every P.T.A meeting. On one such P.T.A meeting, the principle pointed out the examples of four of their teachers who were carpooling for the past several
years. She asked the parents to adopt this method to sort out the problem.
(i) List two values shown by the teachers mentioned by the principal.
(i) Explain two advantages that will occur if more parents emulate the examples of these teachers.
answer.
(a) The two values shown by the teachers mentioned by the principle are:
(i) Eco-friendly lifestyle.
(ii) Coordination and friendship.
(b) (i) Reduction in air pollution and traffic congestion: Carpooling reduces the emission of CO2 into the atmosphere as every car pooling participant takes another car off the road.
(ii) Save money: Carpooling saves money by using less fuel. It reduces the cost involved in repetitive or long distance journeys.
On returning home, Neha, a IXth std. a student noticed that her 6 years old brother Neresh, was watching T.V in the afternoon with all the lights and fans ‘on’. She noticed that the windows were closed and curtains were drawn, which made the room dark, so Naresh had put on the lights. She calmly opened the windows, drew the curtain aside, which illuminated and aerated the room. Then she made Naresh put “off” the lights and made him understand the reason behind her action. (Assume that they are getting electric supply from Thermal Power Plant)
(a) List the two values exhibited by Neha.
(b) Explain how she tried to give the same values to her brother.
answer.(a) The values exhibited by Neha are:
(i) Responsible citizens in the conservation of energy resources.
(ii) Adopt fuel and money saving techniques in her life.
(b) Neha tried to give the same values to her brother Naresh by opening the windows, drawing the curtain aside, which illuminated and aerated the room. This way she shows the practice of adopting renewable sources of energy like solar energy and conserving fossil fuels like coal.
. State the principle of working of ocean thermal energy conversion plants.
Explain how the plant works? Write one essential condition for it to operate
properly.
answer. Principle of working of OTEC: The water at the surface of the ocean is warmer
than the water at deeper depths. This temperature difference can be used by
Ocean Thermal Energy Conversion (OTEC) systems to generate electricity.
Working of OTEC:
In an OTEC plant, the energy of warm surface water is used to convert low i boiling point liquid ammonia into gaseous state.
The vapor of ammonia at high pressure is used to spin the turbines of generators converting the Ocean thermal energy to electricity.
The used vapor passes through the condenser where cold water, pumped from the deeper parts of the ocean condenses ammonia vapor back into a liquid.
This process is repeated again and again ,to get continuous production of electricity.
Essential condition for it to operate properly: The temperature difference between the warmer water at the surface and colder water at depths up to 2 km should be 293 K (20°C) or more.
.Mention why is it not possible to make use of solar cells to meet all our energy needs? State three reasons to support your answer. Also mention three uses of solar cells.
answer. It is not possible to make use of solar cells to meet all our energy needs because:
(i) of limited availability of special grade semiconducting materials such as silicon and germanium.
(ii)solar cells have lower efficiency as they depend entirely on intensity of solar radiation.
(iii) The process of manufacturing solar cells is very expensive, silver used for interconnection of cells in the panel further adds to the cost.
Uses of solar cells:
(i) They provide electric power to satellites and space probes.
(ii) They provide electric power to off-shore drilling platforms and lighthouses.
(iii) TV relay stations or wireless transmission systems located in remote areas use solar panels to get electric power
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