Sources of Energy : Complete Set Question

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This set of questions contains all the possible concepts
which could be asked in the examination

Sources of Energy


Q.1 What is energy crisis?

An energy crisis occurs when we all have a great need of fuel or electricity but does not have enough amounts of them. For example, a large portion of the energy we use is derived from oil. Some experts claim that we will run out of oil in just a few decades

Q.2 Why energy crisis occurs?

When we use energy in its usable form like in cooking, we convert the form of energy and get our work done during the process. Since we cannot reverse the change involved in this process so we cannot get back the original usable form of energy. Due to this, it becomes important to think about energy shortage and the related energy crisis.       

Q.3  List the characteristics of good sources of energy?


What are the qualities of an ideal source of energy?

• It should give large amount of energy per unit mass.

• It should be easy to access.

• It should be easy to store and transport.

• It should be cheap

Q.4  What is a good source of energy?

A good source of energy is the one with following properties:

• It should give large amount of energy per unit mass.

• It should be easy to access.

• It should be easy to store and transport.

• It should be cheap

Q.5  What is a good fuel?

A good fuel is the one with following properties:

• Good fuel should give more heat.

• Should release less smoke.

• Should be cheap.

• Should be easily available.

• Safe

• Should be easy to store.

• Less ash should be left.

• Should have proper burning temperature.

Q.6 The use of dry wood as domestic fuel is not considered as good. State two reasons for it?

The two reasons for dry wood not being a good option for domestic use are:

• It gives very small amount of energy

• It produces lots of smoke.

Q.7 State three criteria for considering charcoal a better fuel than wood for domestic purposes?

The three essential properties for charcoal being a better fuel than wood for domestic use:

• No flame when charcoal is burnt.

• Charcoal produces more energy.

• Charcoal releases less smoke.

Q.8 What do you mean by renewable energy?

Renewable sources of energy are the source which can last for a very long time. It’s supply is unlimited. They are also called non - exhaustible sources of energy. Examples of such type of energy resources are sun, wind, wood and wave etc.

Q.9 What do you mean by non-renewable energy?

Non-renewable sources of energy are sources whose supply is limited and is likely to be finished one day. They are also called exhaustible sources of energy. Examples of such type of energy resources are coal, petrol etc.

Q.10 List two uses of energy in our daily life?

Two uses of energy in daily life is:

• Cooking

• Running Automobiles


Q.11 Name  three conventional sources of energy?

• Fuel

• Wind

• Bio-mass

 Q.12 List two non conventional sources of energy?

• Solar energy

• Nuclear energy

Q.13 State the reason for calling fossil fuels as non-renewable source of energy?

Fossil fuel are called non-renewable source of energy as they are limited and will be over within few decades.

Q.14 Name the major constituent in natural gas?


Q.15 What are the causes of acid rain?

Due to air pollution, oxides of sulphur and nitrogen are present in air. When it rains, these oxides react with rain water to form acids. This acid falls on earth surface along with rain. This is the cause of acid rain.

Q.16 Write the characteristics features of the micro-organisms which help in the production of biogas plant?

These micro-organisms do anaerobic decomposition of slurry to form methane and other components of bio gas.

Q.17 Name two combustible components of bio-gas?

• Methane

• Hydrogen

Q.18 The chief constituent of biogas is methane. List any two other constituents of bio-gas?

• Carbon Dioxide

• Hydrogen

Q.19 Why is a biogas plant a safe and efficient method of waste disposal? Justify.

Biogas plant is a safe method of waste disposal as the waste will no longer create any pollution. Also the remains of this waste material after use in biogas plant can be used as manure.

Biogas plant is an efficient method of waste disposal as now it will be used to produce bio-gas which is a good source of energy. Also the remains of this waste material after use in biogas plant can be used as manure.

Q.20 Mention any one reason due to which most of the thermal power plants are set up near coal or oil fields?

The Thermal plants need coal or oil for production of electricity. But the cost of transporting coal or oil from one place to another is very high. So to reduce this cost, thermal plants are set up near coal and oil fields.

Q.21 Mention the source of energy in the working of a hydro power plant?

The energy possessed by running or falling water is the source of energy to a hydro power plant. By the way, sun is the ultimate source of energy for the hydro power plant.

Q.22 Name the kind of energy possessed by wind and the device used to harness it?

Winds possess wind energy and it is harnessed by wind mills.

Q.23 Blowing wind carries kinetic energy. Mention the two factors that cause winds to blow?

The factors responsible for wind to blow are:

• Temperature difference on the surface of earth.

• Rotation of Earth.

Q.24 Mention the minimum wind velocity required for obtaining electric power with a windmill generator?


Q.25 List any two advantages of using wind energy?

Two advantages of using wind energy are:

• Pollution free

• Renewable

Q.26 Giving a schematic diagram of biogas plant, explain the production of biogas and manure. Give the composition of Biogas?

• Biogas plant is generally made of bricks.

• The various forms of biomass are mixed with in equal quantity of water in the mixing tank. This forms the slurry.

• The slurry is fed into the digester through the inlet chamber.

• Anaerobic microorganisms decompose slurry to form Methane (75%), CO2, H2 gas and H2O. Gases are stored in chamber.

• These gases are called bio-gas.

Q.27 What is biogas?

Biogas is a mixture of methane, carbon dioxide, hydrogen and water vapours which is formed by anaerobic decomposition of bio-waste.

Q.28 Why is the use of biogas obtained from cow-dung advised in preference to burning of cow-dung cakes?

Bio-gas is preferred over cow-dung as bio-gas burns with no smoke and no ash. Cow-dung produces lots of smoke and ash on burning.

Q.29 What is biomass?

Biomass is a source of energy that is directly obtained from plants and animals such as wood, agricultural waste, gobar (cow-dunk).It produces less energy and releases lot of smoke

Q.30 Name the reaction that takes place in biogas plant. Write main constituent of biogas. List two reasons for considering the biogas an ideal fuel for domestic use?

The reaction in biogas plant is anaerobic decomposition.  The main constituents of bio gas are methane, carbon dioxide, hydrogen and water vapours. Biogas is an ideal fuel for domestic use as it produces no smoke and no ash on burning.

Q.31 Explain the function of digester in a biogas plant.

The slurry is fed into the digester through the inlet chamber. It is here in the digester that the slurry is decomposed anaerobically to biogas by microorganisms.

Q.32 Explain the working of a simple turbine?

Turbine is basically a part of dynamo. When the turbine is rotated by flowing water or wind, electromagnetic induction occurs inside the dynamo which results in the production of electricity.

Q.33 Describe how electricity is generated at hydropower plants. List two advantages of producing hydroelectricity?

Dam / reservoir is made over a river to collect water in large amount. Water coming with high speed rotates the turbine, which in turn activates a generator to produce electricity. Some hydroelectric power plants just use a small canal to channel the river water through a turbine.

Advantages of hydro-electricity:

• Very less pollution

• Renewable source of energy 

Q.34 Give two examples to illustrate that energy from windmill was used in the past to do mechanical work?

In old times,  wind mills were used to (i) lift water from well and (ii) to grind grain.

Q.35 What is a wind energy farm? Mention the steps involved in generating electricity from such farms ?

Wind energy farm is a large area with lots of wind mills which are installed for production of electricity in large amount.

The steps involved in production of energy in wind farm are:

• The energy in the wind turns the turbine blades around the rotor.

• A shaft connects the rotor to a generator. When the rotor turns, it spins the generator to make electricity.

•The electrical energy from the generator is transmitted along cables to a substation.

Q.36 List the difference between fossil fuels and solar energy?


Q.37 A hydro power plant converts one form of energy into another. Name these two forms of energy?

Hydro power plant converts mechanical energy of running or falling water to electrical energy.

Q.38 State two advantages of generating hydroelectricity compared to the generation of electricity in thermal power plant?

Two advantages of electricity from hydro power plant over electricity from thermal power plant are:

• Hydro power plant uses renewable source of energy but thermal power plant uses non-renewable source of energy.

•Hydro power plant create very less pollution compared to thermal power plant.

Q.39 Explain how does burning of fossil fuel cause water pollution?

Burning of fossil  fuel causes air pollution. Due to air pollution, oxides of sulphur and nitrogen are present in air. When it rains, these oxides react with rain water to form acids. This acid falls on earth surface along with rain. When this acid rain mixes with water bodies, it causes water pollution

Q.40 Explain how does burning of fossil fuels cause air and soil pollution?

 Burning of fossil  fuel produces harmful gases like oxides of sulphur and nitrogen and dust particles as well. When these gases and dust particles mix with air, they cause air  pollution

 When it rains, these oxides react with rain water to form acids. This acid falls on earth surface along with rain. When this acid rain mixes with soil, it causes soil pollution.

Q.41 State three disadvantages of fossil fuels use (with reason)?

Three disadvantages of fossil fuels are:

• It causes air pollution. When we burn fossil fuel, poisonous gases like oxides of carbon, nitrogen, sulphur are released.

• When these gases release in air, they cause acid rain. When acid rain falls to the earth, it undergoes various physical and chemical changes and causes soil and water pollution.

• Fossil fuels release lots of smoke.

Q.42 What are the problems associated with the construction of big dams?

Problems associated with construction of big dam are:

• Large area is required to build a dam and results is rehabitation of people.  

• Vegetation submerged below dam produces methane which leads to green house effect.

Q.43 Biogas is also known as gobar gas. Justify?

Bio gas is made up of waste products which mainly consist of gobar (cow-dunk). So it is known as gobar gas.

Q.44  List any two advantages of burning charcoal over burning wood?

 Benefits of charcoal over wood:

• No flame.

• Charcoal produces more energy.

Q.45 List two practical uses of biogas in rural areas?

• Cooking

• Street-light

Q.46 How has the traditional use of wind energy been modified for our convenience?

Tradition wind energy was mainly used by wind mills to do small tasks in villages like lifting of water from well or grinding of grain. But now large number of advanced wind mills are installed in wind farms for generation of electricity. This electricity is send to our houses for our use.

Q.47 Define fossil fuels?

These are the fuels formed from remains of dead plants and animals under the earth  crust due to excessive pressure and temperature for millions of years.

Q.48 What are the disadvantages of fossil fuels?

Disadvantages of fossil fuel

• It causes air pollution. When we burn fossil fuel, poisonous gases like oxides of carbon, nitrogen, sulphur are released.

• When these gases release in air, they cause acid rain. When acid rain falls to the earth, it undergoes various physical and chemical changes and causes soil and water pollution.

• Fossil fuels release lots of smoke.

Q.49 Explain working of thermal power plant?

First the coal is burnt into the furnace of steam boiler. High Pressure steam is produced in the boiler. In turbine, this steam force rotates the turbine blades. As the turbine turns, it causes the generator to do its work and create electricity.

Q.50 Name the ultimate source of energy of fossil fuels?


Q.51 Biogas is considered to be a boon to the farmers. Give reasons?

Biogas is really a boom to farmers for following reasons:

• The agricultural waste and gobar from cattle are of not much use to farmers. But now they can be used in biogas plants for generating energy. So, farmers can earn, by selling these waste products.

• The remains of these wastes in biogas plant can further be used by the farmer as manure.

• The biogas thus produces is cheap and can be used by farmer for cooking.

Q.52 Mention any four limitations in harnessing wind energy on a large scale?

Four limitations in setting up wind energy farms on large scale are

• Wind farms can only be established at those places where the wind speed is greater than 15 km/hr.

• Wind turbine cannot work if there is no wind and wind speed is not so high. So we need to store a power backup.

• Requires large area around 1 MW – 2 Hectare land.

• High set up cost.

Q. 54 Which of the following is not an example of a biomass energy source?

(a) Wood
(b) Gobar gas
(c) Atomic energy

(d) Coal ?

b and d

Q.55 State one reason that has necessitated looking for alternate sources of energy?

The convention sources of energy are no more sufficient to supply the massive energy demands of the growing population of this world. So, we need to look for alternate sources of energy.

Q.56 Name a non-conventional renewable source of energy which can be harnessed for 24 hours through the year?

Geothermal energy

Q.57 List two forms of energy in which solar energy manifests itself in oceans?

Wave energy and Ocean-Thermal enrgy

Q.58 Mention the minimum temperature difference required between surface water and the water at depths of upto 2 km in an ocean thermal energy plant.


Q.69 What are hot spots inside earth’s crust?

Earthquakes and magma movement break up the rock covering, allowing heated underground water or steam to accumulate on earth surface. This process is known as geyser and that region where hot water accumulates, is known as hot spot.

Q.60 Mention the limitations in exploiting geothermal energy?

There are very few sites in world were geothermal energy can be exploited.

Q.61 Name any two nuclear fuels used for the process of nuclear fission?

Uranium and plutonium

Q.62 A black surface absorbs more heat radiations as compared to a white or a reflecting surface under identical conditions . List two solar devices which make useof this property in their design?

• Solar cooker

• Solar panel

Q.63 Name any two elements that are used in fabricating solar cells? 

• Silicon

• Selenium

Q.64 If you could use any source of energy for heating your food, which one would you use and why?

LPG is the best choice for cooking purpose because it releases more energy per unit mass, smokeless, does not cause air pollution and ash.

Q.65 Name three forms in which energy from oceans is made available for us. What are OTEC power plants? How do they operate?

The three forms in which energy from oceans is available to us are tidal energy, wave energy and ocean-thermal energy.

OTEP power plants use ocean-thermal energy to generate electricity. Their working is explained as follows:

For working of OTEP, temperature difference between hot and cold layer should be at least 20°C. The hot layer of water at top of ocean is used  to vaporize a working fluid, which has a low boiling point, such as ammonia. The vapor expands and spins a turbine coupled to a generator to produce electricity. The vapor is then cooled by seawater that has been pumped from deeper ocean layer. That condenses the working fluid back into a liquid, so it can be reused. This is a continuous electricity generating cycle.

Q.66 Give one limitation in harnessing energy from sea?

It generally requires very costly initial set up to harness energy from sea.

Q.67 What is meant by nuclear waste? State the main hazard of this waste  on the living beings. How is this waste  disposed off?

The harmful radioactive waste material produced by nuclear plants is called nuclear waste. These nuclear wastes can expose living organisms to harmful radioactive rays which can cause fatal diseases in them for generations to come. These wastes are disposed off in deep pits inside earth surface.

Q.68 Explain solar energy?

Light and heat reaches earth from sun in abundance. This energy from sun can be harnessed to be used to fulfill our needs of energy. This energy is called as solar energy. This solar energy is also the ultimate source of energy to fossil fuels, wind energy and many other forms of energy.

Q.69 Explain the geothermal energy?

The core of earth has very hot magma. The energy possessed by it is geothermal energy.

Q.70 What are the advantages and disadvantages of using a solar cooker?

Advantages of using solar cooker

• No pollution occurs

• No smoke and ash are produced

• Use of renewable source of energy

• No recurring cost once the device is bought and installed.

Disadvantages of using solar cooker

• Cannot be used on cloudy or rainy days.

• Cooking takes more time.

Q.71 Name two components of a solar cooker that are used to increase its heating efficiency .Also explain how they do so?

• A plane mirror or a concave mirror is fixed at the top of the solar panel. This reflects all the light and heat in the area where food is being cooked.

• The interior of the cooker it black colored to absorb maximum heat.

Q.72 Explain the process of nuclear fission. Write the steps involved in generating electricity in a nuclear reactor?

In nuclear fission, large atoms of elements like uranium or plutonium are bombarded by slow moving neutron. The large molecule then breaks into smaller atoms, three neutrons and lot of heat energy. These neutrons react further with more large molecules of uranium or plutonium and thus starting a chain reaction. This generates a lot of energy. This is the process of nuclear fission.

This heat energy generated is used to boil water to steam. This stream rotates the rotor of a turbine which produces electrical energy.

Q.73 Give reasons why large scale making of nuclear energy is prohibited?

• Nuclear waste produced from nuclear plants is very harmful as it emits harmful radiations. It needs to be disposed very properly which is a very difficult task.

• If any accident happens in nuclear power plant, it is very hazardous and can harm the nearby areas for years, generation to generation..

Q.74 Give two advantages of using nuclear energy?

• Can produce huge amount of energy

• Renewable source of energy

Q.75 What is a solar panel? Mention any three of its application?

Solar panels are devices that convert solar light into electricity. Solar panels are comprised of several individual solar cells which are themselves made of silicon.

Uses of Solar Panel:

• Used in satellites and mars probe

• Used in traffic signals and street lights

• Used in houses to replace geysers. 

Q.76 How are the wastes produced in nuclear power plants different from those produced in a thermal power plants?

Wastes in nuclear power plants are radioactive and can be very harmful for generations to come. They can disable people, damage body parts and be fatal. However wastes from a thermal power plant causes air pollution by releasing ashes, which is harmful but not as much as that of the waste from nuclear plants.

Q.77 Why many nuclear power plants could not be installed in our country? Give two reasons?

• Nuclear waste produced from nuclear plants is very harmful as it emits radiations. It needs to be disposed very properly which is a very difficult task.

• If any accident happens in nuclear power plant, it is very hazardous and can harm the nearby areas for years to come.

Q.78 State the energy conversion taking place in the solar cell panel?

Solar energy to electrical energy

Q.79 How is the supply of electricity maintained by a wind mill when there is no wind. By a solar panel when there s no sun?

By back-up battery

Q.80 Mention why is it not possible to make use of solar cells to meet all our energy needs? State four reasons to support your answer.

Solar energy cannot be used to meet all our energy needs because of its following disadvantages:

• Electricity will be produced only on sunny days.

• Special grade silicon is required for making solar cells.

• Manufacturing is expensive.

• Produces low energy.

Q.81 What steps would you suggest to minimize environmental pollution caused by burning of fossil fuels?

• Finding and implementing alternate pollution free sources of energy like CNG.

• Lowering our needs of energy by doing small things in daily life like switching off light when not needed, switching off car engine at red light, wearing sweaters in winter to avoid use of heaters, etc.

Q.82 Write short note on the three sources of energy from ocean

• Tidal energy  Due to gravitational attraction of moon(less or more extent), the level of water in ocean changes twice in a day. When level of water is high, tides are high. When level of water is low, tides are low. Dams or reservoirs are built near seashores to collect the water which comes during a high tide. Turbines in the barrier generate electricity as the tide floods into the reservoir. Once the tide outside the barrier has receded, water retained can then be released through turbines into ocean, again generating electricity.

• Wave energy  Waves are created due to movement of wind on ocean surface. A variety of technologies have been proposed to capture the energy from waves. They can be used in several ways to rotate rotor of dynamo to generate electricity.

• Ocean-thermal energy Ocean thermal energy is a renewable energy technology that harnesses the solar energy absorbed by the oceans to generate electric power. The Sun’s heat warms the surface water a lot more than the deep ocean water, which creates the ocean’s naturally available temperature gradient, or thermal energy.



Q.83  Justify  the statement ‘Hydrogen is a cleaner and more efficient fuel than CNG? If yes, why is it not used in everyday life?

Hydrogen is cleaner fuel that CNG as it makes water on burning which is totally pollution free. CNG produces some harmful gases in small amount on burning, so it does create little bit of pollution.

Hydrogen in not used as a fuel in daily life as it is costly.

Q.84 What are the environmental consequences of the increasing demand for energy?what steps would you suggest to reduce energy consumption?

Any source of energy will definitely cause some pollution. Some sources create more and some less pollution. Due to increasing demand of energy, more and more energy needs to be produced due to which more and more pollution is released. This is not good for the environment.

We can do lots of small things in our daily life to reduce energy consumption:

• Using public transport or walk if the distance is walk-able.

• Avoiding waste of electricity and water

• Switching off the car engine at red light

• Wearing more warm clothes rather than using room heaters

• Using energy efficient appliances

Q.85 Classify  CNG and hydrogen into renewable and non- renewable sources of energy?

Both CNG and Hydrogen comes under renewable sources of energy

Q.86 For which of the following sources of energy, sun is the ultimate source of energy?

(a) Fossil fuel

(b) Hydro power

(c) Biomass

(d) wind energy

(e) Nuclear energy

(f) geothermal

(g) Ocean energy



Value Based Questions : -

Q.1 Mr. Chopra forms an NGO and he approaches Municipal Corporation of a city. He puts a proposal to the corporation that his NGO would collect the waste material and garbage of the city at a particular area and promises them to supply electricity for street lights. In return the corporation has to pay them a nominal amount. The corporation accepted their proposal.

(a) Explain the value exhibited by Mr. Chopra. 

(b) Explain two advantages that occurred to the city by accepting Mr. Chopra’s proposal?

(a) Mr. Chopra is creating a great value. He is making sure that the waste is disposed properly. Not only this, he is actually using the so called waste matters for useful purpose of producing electricity. This helps the society, reduced pollution in environment and makes living standard better.

(b) (i) The problem of waste disposal of the society is solved.

(ii) They will get street lights working at low cost.

Q.2 In an IT firm, there are sixty professionals, MOST OF THEM COME BY THEIR PERSONAL VEHICLE. Most of them come from the same locality.

(a) Will this practice of commuting help the nature? Justify it.

(b) If not, what can they do to help the nature?

(c) What associated values will the learner get from the idea developed to help the nature?  

(a) No, it will not help the nature.

• This practice will harm nature by causing a lot of pollution. All their individual vehicles will cause pollution

• Fossil fuel are non-renewable sources of energy


• Every car can accommodate four to five people comfortably. There can come together in four to five times lesser number of cars. Thus pollution will be heavy reduced.

• Use public transport system

(c) The people who practice this idea of helping nature will save their own money as now lesser fuel needs to be bought. Also while travelling together, they can socialize and develop relations.

Q.3 A school organized a study tour for its students to observe how do people in a village use energy resources for their living? They observed that in one of the village people use wood and cow dung as a fuel while in nearby village they saw modern technology was used by the villagers for better sanitation and management of their bio waste and sewage materials by establishing biogas plant.

(a) If you compare the situation of both the villages, which practice would you prefer to be the best and why? 

(b) State the associated values which you would get from this excursive tour?

(a) The practice in the second village is surely better because:

• Waste product is being used properly and not being littered to cause pollution

• Electricity is being produced at low cost which is improving standard of living in the village

• The remains of the biogas plant can be used as manure in farming.

(b) I learn from such a trip that biogas plants are a wonderful idea, which has lots of advantages for the society. We should adopt the renewable sources of energy.


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