Question : Which of the following is not a bio mass energy source?
a. Nuclear energy
b. Wood
c. Gobar gas
d. Coal
Answer : A
Explanation: Nuclear energy is not a biomass energy source because it is not produced by any type of biological activity but produced from Uranium and Thorium.
Question : Which of the following nuclei are isotopes?
Answer : A
Explanation: Isotopes are the elements with same atomic number but different mass numbers. In the above given elements A and C are having same atomic number 88 but different mass number 226 and 228 respectively.
Question : The conditions for producing biogas is?
a. water but not air
b. Air but not water
c. Neither air nor water
d. Air and water
Answer : A
Explanation: Biogas means a gas produced by the anaerobic digestion or fermentation of organic matter. The organic matter can be manure, sewage sludge, municipal solid waste, biodegradable waste or any other biodegradable feedstock. Biogas is mainly methane and carbon dioxide.
Question : Match the following with correct response.
a. 1-D, 2-A, 3-C, 4-B
b. 1-B, 2-D, 3-A, 4-C
c. 1-A, 2-C, 3-B, 4-D
d. 1-C, 2-B, 3-D, 4-A
Answer : B
Explanation:
i. Fuel burns without smoke is Coke---Coke is a fuel with few impurities and a high carbon content, usually made from coal. It is the solid carbonaceous material derived from destructive distillation of low-ash, lowsulphur bituminous coal. Cokes made from coal are grey, hard, and porous.
... Coke is also used to manufacture water gas ii. Material suitable for producing biogas is Paper scrap---Biogas means a gas produced by the anaerobic digestion or fermentation of organic matter. The organic matter can be manure, sewage sludge, municipal solid waste, biodegradable waste or any other biodegradable feedstock. Biogas is mainly methane and carbon dioxide iii. Production of biogas by biomass is by Anaerobic fermentation--
Biogas is a biofuel produced from the anaerobic fermentation of carbohydrates in plant material or waste (eg food peelings or manure) by bacteria. It is mainly composed of methane, with some carbon dioxide and other trace gases.
iv. Manure is Spent slurry---Bio-Gas produced is also used for Power Generation with the help of genset. The Biogas plant Spent Slurry (rich in nutrients than fresh cow dung) is used as Manure for plantation in gaushala and all around it and this slurry is also vermin-composted and marketed
Question : Match the following with correct response.
a. 1-A, 2-C, 3-B, 4-D
b. 1-D, 2-A, 3-C, 4-B
c. 1-C, 2-B, 3-D, 4-A
d. 1-B, 2-D, 3-A, 4-C
Answer : C
Explanation:
1. A semiconductor is used to develop electric power is Solar cell--- Construction and working of Solar Cell. It essentially consists of a silicon PN junction diode(semiconductor) with a glass window on top surface layer of P material is made extremely thin so, that incident light photon's may easily reach the PN junction. When these photons collide with valence electrons
2. Indirect harnessing of solar energy is from Hydel power plant----
Hydroelectric energy can be defined as a form of hydropower where the motion of running water (kinetic energy) is converted into electricity. The water cycle is driven directly by solar energy. When the sun heats the water in the ocean, some of the water on the surface is vaporized
3. Can be harnessed 24 hours through out the year is Geothermal energy--Geothermal energy is the heat from the Earth. It's clean and sustainable. Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma
4. The temperature in the region of focus is very high in Solar concentrations--Concentrated solar power (also called concentrating solar power, concentrated solar thermal, and CSP) systems generate solar power by using mirrors or lenses to concentrate a large area of sunlight, or solar thermal energy, onto a small area.
Very Short Answers
Question : How is the slurry left in a bio-gas plant, in the end, used?
Answer : The slurry left behind is removed periodically and is used as excellent source of manure, rich in nitrogen and phosphorous.
Question : Name the fuel that provides most of the energy needs of the world.
Answer : Petroleum and coal (fossil fuel) provides most of the energy needs of the world.
Question : Give one disadvantage of nuclear power.
Answer : Nuclear fuels are non-renewable sources of energy and large amount of radioactive materials, which are toxic in nature, are released in the environment which are extremely hazardous to the health of living being for thousands of years. The major disadvantage of nuclear power is Emission and poor management of radioactive waste.
Question : What is a chain reaction?
Answer : • A chemical reaction or other process in which the products themselves promote or spread the reaction.
• The self-sustaining fission reaction spread by neutrons which occurs in nuclear reactors and bombs.
Question : Why a heap of coal or wood does not catch fire at room temperature though sufficient quantity of oxygen is present in air ?
Answer : One of the conditions of combustion to take place is that the fuel temperature should be more than ignition temperature.
Question : Why are many thermal power plants set up near coal or oil fields?
Answer : Thermal Power plant is a power plant where steam is ued to drive a steam turbine and the heat required for the process is obtained from coal and oil .The thermal power plants are usually set up near coal or oil fields so that the fuel can be easily obtained and the problem of air pollution while transporting the fuel may be minimized.
Question : Reena's father works with a company that builds dams. Once he took her to the site, where a dam was being build. Reena saw a group of people sitting there and shouting slogans against the building of 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 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 a boon for many citizens of the country. How?
Answer : i.Reena's father was very proud of his daughter because she resolved the conflict peacefully and smartly.
ii.One of the major disadvantages of the construction of dams is the dislocation of local people. That's why the local people were protesting against it.
iii.Reena acted as a bridge between the local people and the authorities. She helped authorities by convincing people for discussions with them. She also played a major role in the construction of dam which then helped in controlling flood in river and also in irrigation.
Question : Name two energy sources that you would consider to be renewable. Give its reason.
Answer : Solar energy, wave energy, tidal energy, wind energy all are renewable sources of energy.
The solar energy is free and can be used anywhere with ease. Solar energy can be used to produce electric energy in solar cells. It can be used for solar water heaters and in solar cookers.
Wind is also available source of energy almost everywhere and can be used to run wind farms to produce electricity, to draw water from the wells and grind the grains.
Long Answers
Question : What are environmental consequences of the increasing demand for energy ? What steps would you suggest to reduce energy consumption ?
Answer : The demand of energy is increasing day by day. Exploiting any source of energy may disturb the environment in one way or other. For example getting energy from fossil fuel may cause lot of pollution in air. Getting energy by nuclear fission may create problem of disposal of nuclear waste. Steps for reducing energy consumption should be such that we get maximum energy from least fuel. For this:
i. Under the given situation technology utilized should be the best possible. For example using smokeless chulhas should be preferred to traditional chulhas.
ii. Energy should be extracted by most economic method under the given situation.
Whereas energy extraction by solar cell may be useless in big towns due to cost factor, it may be indispensable for artificial satellites.
iii. Wastage of energy should be strictly avoided. Energy saves is equal to energy produced.
iv. Sources of energy should be such that it causes the lease damage to environment.
Question : What is combustion ? What are the essential conditions for combustion to take place?
Answer : A very large number of substances burn in oxygen (presence in air) with the release of large amount of heat and light. Substance which burns in the presence of air is called combustible material. Oxygen present in air helps in burning of the substance and is called supporter of combustion. Chemical reaction responsible for release of energy is called combustion. The substance which burns on heating in oxygen or air is called combustible substance. Wood, coal, paper, coke, hydrogen, CNG (compressed natural gas), LPG (liquefied petroleum gas) kerosene, diesel, alcohol, ether, petrol etc.
Are all examples of combustible substances. Air contains about 21% of oxygen by volume and 78% nitrogen. Whereas nitrogen is neither combustible nor supports combustion. However oxygen is a strong supporter of combustion. If we allow a substance to burn in pure oxygen (as in welding arc), we observe very fast burning.
Kindling or Ignition Temperature : The minimum temperature to which a substance must be heated before it catches fire is called kindling or ignition temperature. If the temperature of the substance is less than kindling or ignition temperature, it will not catch fire even if it is placed in pure oxygen. Ignition temperature of phosphorus is 35oC. Phosphorus will not catch fire if its temperature is less than 35oC. It will catch fire when its temperature is above 35oC. Inflammable substances are those which can easily catch fire. There ignition temperature is very low. It is usually less than 100oC. A minor spark is sufficient to cause serious accident.
Alcohol, carbon disulphide, ether, benzene, petrol, LPG, nylon fibres are inflammable substances. You must have observed that you ignite LPG burner (used by your mother in kitchen) with a gas lighter which gives a very small (point) spark.
Conditions Necessary for Partial/Complete Combustion
i. There must be a combustible substance.
ii. There must be a supporter of combustion.
iii. Temperature of combustible substance is to be more than ignition temperature for the substance.
If any of the three conditions is not obeyed, the combustion will not take place.
Question. Which is the most popular kitchen fuel in India?
Answer : LPG
Question. Which method is used to produce electricity in hydroelectric power plant?
Answer : By running dynamo by kinetic energy
3. Which of the following is the odd one out?
a. Petroleum.
b. Hydro electricity.
c. Coal
d. CNG
Answer : B. Hydroelectricity.
Question. Which method is used to produce electricity in thermal power plant?
Answer : By boiling water.
Question. Which of the following is a component of bio-gas?
a. Methane
b. LPG
c. CNG
d. Hydrogen sulphide
Answer : Methane
Question. Which produces energy because of temperature difference at various levels in ocean.
Answer : ocean thermal energy
Question. Which energy source is the largest source used in India?
Answer : Sun
Question. Which of the following is normally used in solar cookers for trapping solar energy?
a. Solar panels
b. Siilicon cells
c. Mirrors
d. Any of above
Answer : Mirrors (for reflecting the sun rays)
Question. In which of the following kinetic energy is converted into electrical energy?
a. Tidal energy
b hydro energy.
C. Wind energy
d. All of these
Answer : All of these
Question. Which of the following is the ultimate source of energy for us?
a. LPG.
b. Nuclear
c. Solar.
d. CNG
Answer : Solar
Short questions Answers
Question. What is a good source of energy?
Answer : The energy which is easily available, cheap, does not produce pollution is said to be good source.
Question. What is a good fuel?
Answer : A good fuel is one which is cheap, easily available, easy to handle, transport, has proper ignition temperature and high calorific value.
Question. What are the disadvantages of fossil fuels?
Answer : Disadvantages of fossil fuels are:
(a) They are non-renewable resources
(b) They cause pollution which can lead to
(i) Acid rain
(ii) Smoke
(iii) Green house effect due to CO2
(iv) Fly ash suspended in air.
Question. Why are we looking at alternate sources of energy?
Answer : The sources of energy we are using now is fossil fuel i.e., petrol and petroleum products, and coal which are exhaustible and non-renewable. The demand of energy is increasing due to increased population and better technology that has added many machines, appliances to add comfort to life style. Hence ,the. demand for energy is increasing day by day. To overcome this problem we are looking for alternate sources of energy.
Question. How has the traditional use of wind and water energy been modified for our convenience?
Answer : (i) The traditional use of water energy has been modified and we have built dams, turbines and dynamos to generate electricity with the help of flow of water.
(ii) Wind; energy is used to rotate the wind mills, turbines and generate electricity by constructing wind fAnswer :
Question. What kind of mirror-concave, convex or plain-would be best suited for use in a solar cooker? Why?
Answer : Concave minor would be best suited for use in solar cooker. As it is a converging mirror and would converge sun heat radiation at one focussed point.
Question. What are the limitations of the energy that can be obtained from the oceans?
Answer : The limitations of ocean energy are: (i) Few limited sites/places where this wave, tidal or ocean thermal energy can be obtained. (ii) The cost of construction of plants is very; high (iii) The efficiency of producing energy is also low
Question. What is geothermal energy?
Answer : The heat energy obtained in the form of steam from under the earth’s crust is called geothermal energy
Question.. What are the advantages of nuclear energy?
Answer : The advantages of nuclear energy are: (i) A very small amount of radioactive material can produce large amount of energy which can be controlled and converted into usable form e.g., 1 kg Uranium = 25 thousand tonnes of coal. (ii) It does not release any smoke or harmful gases in the air. Hence it can, curbthe global warming that is caused due to green house effect.
Question. Can any source of energy be pollution free? Why or why not?
Answer : Yes, there can be a source of energy that can be pollution free in using it. e.g., sun’s energy that is used in solar cooker, solar water heater, solar cell panels.
Question. Hydrogen has been used as a rocket fuel. Would you consider It a cleaner fuel than CNG? Why or why not?
Answer : Hydrogen is a cleaner fuel than CNG because hydrogen on burning/combustion form water whereas CNG that contain methane burns to produce carbon dioxide.
Question. Name two energy sources that you would consider to be renewable. Give reasons fur your choices.
Answer : Solar energy-it will not get exhausted it can be used for multipurpose-heating, burning and producing electricity. It will not cause any pollution, it is cheap and easily available. Energy from water-Energy can be obtained from water in various form i.e., for producing electricity without pollution.
One linear questions :-
Question. A solar water heater cannot be used to get hot water on………..,…
Answer : ) a cloudy day.
Question. Which of the following is not an example of a bio-mass energy source?
(a) wood
(b) gobar-gas
(c) nuclear energy
(d) coal
Answer : (c) nuclear energy.
Question. 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 ?
Answer : (c) nuclear energy.
Question. Compare and contrast fossil fuels and the Sun as direct sources of energy.
Answer : Sun
1. It is renewable source of energy.
2. It does not cause pollution.
3. It is cheap, easily available for most of the time and at most of the places.
Fossil fuels
1. It is non-renewable source of energy.
2. It causes pollution in the environment.
3. It is expensive, not easily available ai1y time and anywhere.
Question. Compare and contrast bio-mass and hydro electricity as sources of energy.
Answer :
Bio-mass as Energy Source
1. It causes pollution.
2. It is cheap and easily available.
3. Initial cost for building the bio-gas plant is very cheap and its maintenance is also cheap.
Hydro electricity as Energy Source
1. It does not cause pollution.
2. It is expensive and not easily available.
3. The initial cost of building the power plant is expensive, its maintenance is also expensive.
Question. What are the limitations of extracting energy from:
(a) the wind?
(b) waves?
(c) tides?
Answer : (a) The Wind
(i) It can be extracted only at limited sites where the wind blows most of the time in a year.
(ii) The minimum speed of wind should be 15 km/h.
(iii) Large area is required to build the wind farm/wind mills which is expensive affair.
(iv) Efficiency, is low.
(b) Waves (i) The place and time is limited when the waves are strong.
(ii) Initial setup cost is expensive.
(iii) Efficiency is low.
(c) Tides
(i) The areas where tidal energy can be harnessed is less.
(ii) The efficiency is very low.
(iii) The plants are not cost effective.
Question. On what basis would you classify energy sources as
(a) renewable and non-renewable?
(b) exhaustible and inexhaustible?
Answer : Both (a) and (b) options are same:
Renewable/Inexhaustible
1. They are also called inexhaustible
2. The energy source that will not finish and can be renewed or made again and again is called renewable source of energy e.g., sun, wind, water.
Non-renewable/Exhaustible
1. They are also called as exhaustible
2.The energy source that will finish and will get exhausted and cannot be made very soon or takes million of years for its formation e.g., fossil fuels-petrol, coal.
Question. What are the qualities of an ideal source of energy?
Answer : he ideal source should have the following qualities:
1. should be cheap, easily available and easy to handle.
2. It can be transported easily.
3. It should have high calorific value.
4. It should have proper ignition. temperature.
5. It should not cause any environmental pollution.
Question. What are the advantages and disadvantages of using a solar cooker.? Are there places where solar cookers would have limited utility?
Answer : Advantages of solar cooker:
(a) It is cheap and easy to handle.
(b) It does not need any fuel for cooking food.
(c) It is pollution free.
Disadvantages of solar cooker:
(a) It is very slow, takes long time for cooking.
(b) It is dependent on sun's light, cannot work on cloudy day.
(c) The reflectors position need to be monitored so as it reflects the sunlight at the centre focused point of the solar cooker. Yes-the places where sun’s energy not sufficient, the use of solar cookers would be limited
Question. What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Answer : Due to increasing demand of energy the available sources of energy are depleting at fast rate. The use of fuels on large scale is releasing lot of gases and unwanted particles in the air. The gases like SO2, NO2 are causing acid rain that is destroying monuments, iron articles, bridges etc. The CO2 released in air is causing green house effect that is leading to global warming which will melt the ice and sea-level will increase submerging coastal areas and islands. To reduce energy consumption we should look for alternative source of energy which can help us to overcome all these problems.
SourceS of energy
Question. What is a good source of energy?
Answer : A good source of energy should have the following qualities-
(1) It should be easily available.
(2) It should have high calorific value.
(3) It should be easy to store and transport.
(4) It should be economical.
(5) It should cause less environmental pollution.
Question. What is a good fuel?
Answer : A good fuel should have the following qualities-
(1) It should be easily available.
(2) It should have high calorific value.
(3) It should be easy to store and transport.
(4) It should be economical.
(5) It should cause less environmental pollution.
Question. If you could use any source of energy for heating your food, which one would you use and why?
Answer : We shall use LPG/CNG gas or electricity for heating our food because these are have all properties of good fuel.
Question. What are the disadvantages of fossil fuels?
Answer : There are following disadvantages of fossil fuels like coal and petroleum-
(1) Burning of coal or petroleum causes air pollution.
(2) Burning of fossil fuels produce gasses responsible for acidic rain and green house effect.
(3) Fossil fuels are non-renewable sources of energy.
Question. Why are we looking at alternate sources of energy?
Answer : Because traditional sources of energy like coal, petroleum are non renewable sources, have limited sources on earth. Also these cause pollution. So we are looking at alternate sources.
Question. How has the traditional use of wind and water energy been modified for our convenience?
Answer : (1) Wind energy is converted into electricity by wind mills.
(2) Energy of moving water is also converted into electricity by the use of dams and generators.
Question. What kind of mirror – concave, convex or plain – would be best suited for use in a solar cooker? Why?
Answer : Concave mirrors are used in soalr cooker. Because concave mirrors converge the light incident on them at a single point to produce a large amount of heat.
Question. What are the limitations of the energy that can be obtained from the oceans?
Answer :
(1) Limitations Tidal energy-There are very few locations where dams to utilize tidal energy can be built and these cannot work all the time.
(2) Limitations of wave energy- There are limited locations with high strength waves.
(3) Limitations of Ocean thermal energy- To get electricity from ocean thermal energy OTEC plants are made.
This plant is very costly and can work only when there is temperature difference of minimum 20°C between sea level and some depth.
Question. What is geothermal energy?
Answer : Geothermal energy is the heat energy present inside earth in certain regions called hot spots. When underground water comes in contact with the hot spot, steam is generated. This steam is routed through a pipe to a turbine and used to generate electricity.
Question. What are the advantages of nuclear energy?
Answer : Electricity can be produced by nuclear fission reaction in nuclear reactor. Calorific value of nuclear sources are very high. Atomic bomb is also based on nuclear fission reaction. Sun and other stars produce a huge amount of energy by nuclear fusion reaction.
Question. Can any source of energy be pollution-free? Why or why not?
Answer : No, any source of energy cannot be pollution free. Solar cell like pollution free sources also produce
pollution while production or destruction.
Question. Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?
Answer : Hydrogen is cleaner fuel than CNG because on burning hydrogen produce only water, but CNG produce green house gasses. Beside this hydrogen’s calorific value is very high.
Question. Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Answer : Solar, water and wind energy are renewable sources because these cannot be exhausted. Bio-mass and wood are also renewable sources of energy as these can be replenished again in some time.
Question. Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
Answer : Coal and petroleum are two exhaustible sources of energy. These fuels were formed over millions of years ago and there are only limited reserves. If we continue to use them as at present, these reserves will be exhausted very soon.
EXERCISE QUESTION-ANSWERS
Question. 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.
Question. Which of the following is not an example of a bio-mass energy source?
(a) wood
(b) gobar-gas
(c) nuclear energy ✓
(d) coal
Question. Most of the sources of energy we use represent stored solar energy. Which of the following is not ultimately derived from the Sun’s energy?
(a) geothermal energy
(b) wind energy
(c) nuclear energy ✓
(d) bio-mass.
Question. Compare and contrast fossil fuels and the Sun as direct sources of energy.
Answer-
Fossil fuels Sun
1. These are non-renewable sources of energy. 1. This is a renewable source of energy.
2. These cause pollution. 2. It do not cause pollution.
3. These will exhaust in near future. 3. It will last as the solar system exist.
4. Energy can be produced any time. 4. Energy can only be utilized at day time in sunshine.
Question. Compare and contrast bio-mass and hydroelectricity as sources of energy.
Answer-
Bio-mass Hydroelectricity
1. This is a renewable source of energy. 1. This is a renewable source of energy.
2. It causes pollution. 2. It do not cause pollution.
3. Energy can be produced anytime, anywhere. 3. There are limited places where hydroelectric
power plants can be developed.
Question. What are the limitations of extracting energy from — (a) the wind? (b) waves? (c) tides?
Answer- (a) Limitations of wind energy-
(1) Initial cost of wind mill plant is very high.
(2) For proper working of will mills, speed of wind must be more than 15 km/h, but this is not possible for the whole year.
(3) There are limited places where wind mill plant can set up.
(4) A large area is required to set up a wind mill plant.
(b) Limitations of wave energy- There are limited locations with high strength waves.
(c) Limitations tidal energy-There are very few locations where dams to utilize tidal energy can be built and these cannot work all the time.
Question. On what basis would you classify energy sources as
(a) renewable and non-renewable?
(b) exhaustible and inexhaustible? Are the options given in (a) and (b) the same?
Answer- (a) The source of energy that replenishes in nature is known as renewable source of energy. Sun, wind,moving water, bio-mass, etc. are some of the examples of renewable sources of energy.
The source of energy that does not replenish in nature is known as non-renewable source of energy. Coal, petroleum, natural gas, etc. are some of the examples of non - renewable sources of energy.
(b) Exhaustible sources are those sources of energy, which will deplete and exhaust after a few hundred years.Coal, petroleum, etc. are the exhaustible sources of energy.
Inexhaustible resources of energy are those sources, which will not exhaust in future. These are unlimited.Bio-mass is one of the inexhaustible sources of energy.
Yes. The options given in (a) and (b) are the same.
Question. What are the qualities of an ideal source of energy?
Answer- An ideal source of energy should have the following qualities-
(1) It should be easily available.
(2) It should have high calorific value.
(3) It should be easy to store and transport.
(4) It should be economical.
(5) It should cause less environmental pollution.
Question. What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?
Answer- Advantages of using solar cooker-
(1) This is pollution free.
(2) Free Sun energy is utilized.
(3) It do not destroy nutrients of food.
Disadvantages-
(1) It cannot work at night or during clouds.
(2) Reflector of solar cooker must be directed towards Sun from time to time.
(3) High temperature cannot be attained.
(4) It takes a lot of time to hot the food.
Question. What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Answer- Environmental consequences of the increasing demand for energy-
(1) Gasses evolved during burning of fossil fuels increase green house effect.
(2) Gasses evolved during burning of fossil fuels are responsible for acidic rain.
(3) Gasses evolved during burning of fossil fuels cause air pollution.
(4) High energy demand result in deforestation, which cause less rain, soil erosion etc.
(5) Wastages of nuclear reactor are very dangerous.
Steps to reduce energy consumption-
(1) Lights and fans should be turned ‘ON’ only when needed.
(2) We should use energy efficient appliances.
(3) We should use bio-gas plant in rural area.
(4) We should use fuels which cause less pollution.
(5) We should use pressure cooker for cooking.
(6) We should use public transport instead of private vehicles.
(7) We should use cycle instead of bike
