Important Questions Class 10 Science Chapter 14

Important Questions Class 10 Science Chapter 14 – Sources of Energy

The fourteenth chapter of the Class 10 CBSE Science syllabus educates students about “Sources of Energy”. Our need for energy rises along with our standard of living. We work to increase energy consumption efficiency and explore new energy sources in an effort to meet our energy needs. This chapter examines many energy sources, all of which are traditional sources of energy that humans have been using for a long time. There are both merits and demerits to using renewable and non-renewable energy sources. As a result, they ought to be used carefully. The non-renewable resources are close to running out, and thus students should have better conceptual clarity for working out solutions in the near future.

Extramarks provides comprehensive education resources to students from Class 1 to Class 12. Revisions with regular practise questions are crucial for any student to gain a better understanding of science topics. Our team has created a question bank of Science Class 10 Chapter 14 Important Questions which collates questions from different sources. So students don’t have to look at any other multiple sources for further reference.

It is crucial that all of the topics are covered for our students to succeed. As a result, we have included numerous sets of questions from various references and sources in the Important Questions Class 10 Science Chapter 14 to help students understand each idea covered in the chapter in the form of important questions and step-by-step detailed solutions.

It includes questions taken from the NCERT textbook, the NCERT Exemplar, and numerous other reference materials. A group of science experts have selected the questions and prepared the solutions. Students are assured that they are studying from the right material because the team has carefully chosen and drafted the questions based on the NCERT books and  latest CBSE syllabus and exam guidelines.

CBSE Class 10 Science Important Questions 2022-23

CBSE Class 10 Science Important Questions are also available for the following chapters:

CBSE Class 10 Science Important Questions
Sr No. Chapters
1 Chemical Reactions and Equations
2 Acids, Bases and Salts
3 Metals and Non-metals
4 Carbon and Its Compounds
5 Periodic Classification of Elements
6 Life Processes
7 Control and Coordination
8 How do Organisms Reproduce?
9 Heredity and Evolution
10 Light Reflection and Refraction
11 Human Eye and Colourful World
12 Electricity
13 Magnetic Effects of Electric Current
14 Sources of Energy
15 Our Environment
16 Management of Natural Resources

Important Questions Class 10 Science Chapter 14 – With Solutions

Our Science subject matter experts have compiled different formats of questions along with their detailed solutions in the form of a question bank which comprises Important Questions Class 10 Science Chapter 14. Solving the questions before the board exams will help students identify their weaknesses. The given solutions will allow students to get clarity on concepts where they are weak. Also, by simply going through the solutions, students get familiar with the format of answers that will help them score good marks.

The complete study guide of NCERT solutions and our question bank for Class 10 Science will be helpful for students taking the board exams. The students will undoubtedly perform better on the tests if they thoroughly practise all the questions.

Given below is a set of questionnaires and their solutions that are included in our Class 10 Science Chapter 14 Important Questions:

Question 1: Acid rain happens because

(a) Earth’s atmosphere contains acids

(b) burning of fossil fuels releases oxides of carbon, nitrogen and sulphur into the atmosphere

(c) sun leads to heating of the upper layer of the atmosphere

(d) electrical charges are produced due to friction amongst clouds

 Answer 1: (b)


Rainwater combines with atmospheric carbon, nitrogen, and sulphur oxides to form acid rain.

Question 2:  Fuel used in thermal power plants is

(a) biomass

(b) uranium

(c) water

(d) fossil fuels

Answer 2: (d) fossil fuels


The primary fossil fuel utilised in thermal power plants is coal. Petroleum and natural gas are also used in addition to coal.

Question 3:  In a hydropower plant

(a) Potential energy possessed by stored water is converted into electricity

(b) Water is converted into steam to produce electricity

(c) Electricity is extracted from water

(d) Kinetic energy possessed by stored water is converted into potential energy

Answer 3: (a)


Dammed water has the ability to produce energy. It has potential energy when it is released, which is used to turn the turbines. Electricity is produced via turbines.

Question 4:  Which is the ultimate source of energy?

(a) Water

(b) Sun

(c) Fossil fuels 

(d) Uranium

Answer 4: (b)


Solar energy is used by plants to make food. Plant remains are used to create fossil fuels. Therefore, all energy comes from the Sun, either directly or indirectly.

Question 5:  Which one of the following forms of energy leads to the least environmental pollution in the process of harnessing and utilisation?

(a) Geothermal energy 

(b) Thermal energy

(c) Solar energy

(d) Nuclear energy

Answer 5: (c)


Metals like uranium, which emit dangerous radiation that can harm living things, are used in nuclear energy. Coal is used to generate thermal energy, which pollutes the air by releasing sulphur and carbon dioxide. In the case of geothermal energy, the pressure from the heat from the core, which can occasionally be extremely intense and dangerous, absorbs the energy.

Question 6:  A solar water heater cannot be used to get hot water on

  1. A windy day 
  2. A cloudy day
  3. A hot day
  4. A sunny day

Answer 6:  b) A cloudy day

A solar water heater uses solar energy to heat water. The sunlight is reflected back into the sky by the clouds during overcast days because it isn’t strong and bright enough. As a result, the Sun cannot reach the ground. As a result, the solar water heater won’t be able to heat the water using solar energy.

Question 7:  Which of the following is not an example of a biomass energy source?

  1. Wood
  2. Coal
  3. Nuclear energy
  4. Gobar-gas

Answer 7:  c) Nuclear energy.

Animal and plant wastes are used to create biomass. These deceased plants and animals undergo a chemical transformation as a result of their interactions with water and sunlight. However, nuclear energy is created when atoms fuse and split, releasing enormous amounts of energy in the process. It is possible to carry out nuclear fusion and fission without sunshine.

Wood is a component of plants, gobar gas is made from animal waste, and coal is made from the decomposing bodies of plants and animals. They are all results of biomass energy products.

Question 8:  Most energy sources we use represent stored solar energy. Which of the following is not ultimately derived from the Sun’s energy?

  1. Geothermal energy
  2. Biomass 
  3. Nuclear energy
  4. Wind energy

Answer 8:  c) Nuclear energy.

Nuclear fusion and nuclear fission are both sources of nuclear energy. When uranium atoms are subjected to nuclear fission, low-energy neutrons cause the atom to divide into two relatively lighter nuclei. Lighter nuclei are fused together to create relatively heavier nuclei in nuclear fusion. Nuclear reactions can occur without sunshine and yield enormous amounts of energy.

Geothermal energy is produced from the heat that is deep within the earth’s crust and has been stored there as energy. The wind is caused by the uneven heating of the earth’s surface, while biomass is made from the dead remnants of plants and animals.

Question 9:  Ocean thermal energy is 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 arising out in the ocean

Answer 9: (b)


Energy primarily from the surface is used to boil the volatile liquid, whereas vapours from these are utilised to turn the turbine.

Question 10:  The major problem in harnessing nuclear energy is how to

(a)convert nuclear energy into electrical energy?  

(b) sustain the reaction?

(c) dispose of spent fuel safely?

(d) split nuclei?

Answer 10: (c)


Highly radioactive material is created by nuclear power reactors. They pose a serious hazard to living things when they are discharged into the environment. So, one of the biggest challenges in using nuclear energy is safely disposing of the spent material.

Question 11:  Which part of the solar cooker is responsible for the greenhouse effect?

(a) Outer cover of the solar cooker 

(b) Mirror

(c) Glass sheet

(d) Coating with black colour inside the box

Answer 11: (c)


The atmosphere’s ability to trap heat is what causes the greenhouse effect. Heat is created due to the presence of greenhouse gases like CO2 and SO2. Similar events take place in solar cookers. The glass sheet reflects the solar energy trapped and causes the food to cook.

Question 12: The main constituent of biogas is

(a) methane

(b) hydrogen sulphide

(c) hydrogen

(d) carbon dioxide

Answer 12: (a)


The primary byproduct of biogas is methane gas. Methane makes up about 70% of the gas produced, with the remainder being made up of ammonia and carbon dioxide.

Question 13: The power generated in a windmill

(a) can be increased by planting tall trees close to the tower

(b) depends on the height of the tower

(c) depends on wind velocity

(d) is more in the rainy season since damp air would mean more air mass hitting the blades

Answer 13: (c)


High wind speeds will cause the turbine to spin more quickly. As a result,  more electricity will be generated.

Question 14:  Choose the correct statement

(a) Sun can be taken as an inexhaustible source of energy

(b) Waste from a nuclear power plant can be easily disposed of 

(c) Hydro and wind energy plants are non-polluting sources of energy

(d) There is infinite storage of fossil fuel inside the earth

Answer 14: (a)


A finite source, fossil fuels are. By altering the environment and having an impact on the land usage, habitations, and natural ecosystems in the dam region, hydro and wind energy projects can have significant negative environmental effects. The primary challenge a nuclear facility faces is how to dispose of its waste.

Question 15:  Choose the INCORRECT  statement regarding wind power

(a) One possible method of utilising the energy of rotational motion of the blades of a windmill is to run the turbine of an electric generator

(b) The potential energy content of wind blowing at high altitudes is the source of wind power

(c) It is expected to harness wind power to a minimum in open space 

(d) Wind hitting the blades of a windmill causes them to rotate. The rotation thus achieved can be utilised further

Answer 15: (b)


The kinetic energy of the wind drives wind power.

Question 16:  Choose the INCORRECT  statement

(a) We are encouraged to plant more trees so as to ensure a clean environment and also provide biomass fuel

(b) Biomass is a renewable source of energy 

(c) The main ingredient of bio-gas is ethane, and it gives a lot of smoke and also produces a lot of residual ash

(d) Gobar-gas is produced when crops, vegetable wastes etc., decompose in the absence of oxygen

Answer 16: (c)


Methane is a biogas’ main byproduct.  When it burns it doesn’t leave behind any ash.

Question 17:  What are geothermal energy hot spots?

Answer 17:

Molten rocks that develop in the deeper, hotter layers of the earth’s crust are forced upward and trapped in some areas as a result of geological changes. Hot spots are the names for these areas.

Question 18: 

Name the phenomenon that explains the working of an electric generator.

Answer 18:

The phenomenon explaining the working of an electric generator is electromagnetic induction.

Question 19: 

State an important advantage of using AC over DC.

Answer 19:

AC compared to DC,  AC voltages can be readily transformed to higher or lower voltage levels, while it is difficult to do that with DC voltages. It can be transmitted across long distances with little loss of electric power.

Question 20: 

Name one material used to make a solar cell and also mention the range of voltage produced by a typical cell.

Answer 20:

A solar cell is made of silicon. Voltage in a normal cell ranges from 0.5 to 1 V.

Question 21: 

Write the name of the substance whose vapours are used to run the turbine of the generator of the ocean thermal energy plant.

Answer 21:

Volatile liquid ammonia.

Question 22: 

Name the energy obtained from sea or ocean water due to the difference in temperature at the surface and in deeper sections of these water bodies.

Answer 22:

Ocean thermal energy conversion(OTEC).

Question 23: How is hydropower harnessed?

Answer 23:

Water contained in a dam’s potential energy is transformed into the kinetic energy of water falling, which is eventually transformed into electrical energy.

Question 24: Define 1 MW.

Answer 24:

A device that consumes or dissipates 1 megajoule of energy per second is said to consume or dissipate 1 MW of power.

Question 25: Mention two disadvantages of constructing Tehri Dam.

Answer 25:

Around 100,000 people or more have been displaced in order to build the Tehri Dam, which sparked considerable unrest and legal disputes. Large ecosystems were also devastated due to the loss of biodiversity when they were submerged under the water in dams, which led to the emission of a lot of methane, a greenhouse gas.

Question 26: What happens when water from great heights is made to fall on the blades of the turbine?

Answer 26:

When water is made  to fall from great heights, its potential energy is transformed into kinetic energy, which, when it strikes turbine blades, rotates a generator to produce electricity.

Question 27.

Why is biogas considered an excellent fuel?

Answer 27: Biogas is considered an excellent fuel because

  • it does not produce smoke.
  • Left behind slurry can be used as excellent manure.

Question 28: Name any two nutrients that the spent slurry has in the biogas plant.

Answer 28: Nitrogen and phosphorus.

Question 29: Write the energy conversion that takes place in a hydropower plant.

Answer 29: The potential energy of water that has been stored is converted into electrical energy by hydropower plants.

Question 30: Name any two fossil fuels.

Answer 30: Coal and petroleum are two fossil fuels.

Question 31:  Name any two conventional sources of energy. 

Answer 31:

(i) Fossil fuels (ii) Wind energy

Question 32: 

What is meant by the term ‘Biomass’?

Answer 32:

Biomass: Biomass is any plant substance that can decay in the absence of oxygen, such as cow dung, other plant materials like crop residue after harvest, vegetable wastes, and sewage.

Question 33: 

Write the characteristic features of the microorganisms which help in the production of biogas in a biogas plant.

Answer 33:

Anaerobic microorganisms are utilised in biogas plants. They can break down and degrade the complex molecules in the cow dung slurry without the need for oxygen.

Question 34: 

What are fossil fuels? “Burning fossil fuels may lead to intense global warming.” Justify this statement.

Answer 34:

Fossil fuels: Fossil fuels are combustible materials created from dead plants and animals that have been buried deep beneath the earth’s surface for millions of years.

Carbon dioxide is produced when fossil fuels are burned, and too much of it in the atmosphere has a greenhouse effect that promotes rapid global warming.

Question 35: 

What are the main components of biogas? How is biogas obtained from biomass? Write any two advantages of using this gas.

Answer 35:

Methane makes up 75% of biogas’s composition. Biomass is broken down anaerobically in a biogas plant to produce biogas. The two advantages of using biogas are

  • smoke-free cooking.
  •  has a high calorific value.

Question 36: 

Define: (i) Anaerobic degradation

Answer 36:

(i) Anaerobic degradation: Anaerobic degradation refers to the breakdown of big organic compounds into simpler ones without the presence of air.

Question 37: 

Explain the process of biogas production in a biogas plant. 

Answer 37:

Working of the biogas plant:

In the mixing tank, dung and home and agricultural waste are combined with water. The digester’s inlet chamber receives the slurry that was produced in this manner. Biogas is produced as anaerobic fermentation gradually takes hold. A new biogas plant must run for around 6 to 8 weeks before it can begin producing biogas at a respectable pace. The spent slurry is then  forced into the outlet chamber and then into the overflow tank as the biogas pressure inside the dome rises. The used slurry is utilised as manure in agricultural fields since it is a rich source of plant nutrients.

The gas valve can be spun to remove biogas for supply. Dung slurry is then fed into the digester and periodically withdrawn from it to keep the biogas plant running constantly.

Question 38: 

List any four disadvantages of using fossil fuels for the production of energy.

Answer 38:

The disadvantages of using fossil fuels for the production of energy are :

  • These are non-renewable sources of energy.
  • It releases pollutants into the air.
  • Its formation takes millions of years
  •  It causes acid rain.

Question 39: 

State the difference between energy obtained by burning fossil fuels and that obtained as solar energy. 

Answer 39:

  • The reserves of fossil fuels are finite or exhaustible, whereas the supply of solar energy is limitless and abundant or inexhaustible.
  • Solar energy is pollution-free, but fossil fuels produce pollution when they are burned.
  • While solar energy is unavailable when the sky is overcast, fossil fuels can supply energy whenever it is needed.

Question 40: 

Define the process of nuclear fission. Write the steps involved in generating electricity in a nuclear reactor. 

Answer 40:

Nuclear fission is the process by which a heavy nucleus splits into two fragments of comparable mass after being bombarded by slow-moving neutrons, along with the release of two or more fast-moving neutrons and a significant quantity of energy.

Steps involved in generating electricity:

  • Slowly travelling neutrons are used to attack big atoms like uranium or plutonium.
  • Lots of heat energy is released when large atoms shatter.
  • Water is heated to a steamy state using this heat.
  • The turbine that generates energy is rotated by this steam.

Question 41:  Why is there a need to harness non-conventional sources of energy? Give two main reasons.

Answer 41: Following are the reasons for the need to harness non-conventional sources of energy.

  1. The use of conventional energy sources will eventually run out because they are an exhaustible resource.
  2. Environmental pollution was not caused by unconventional sources of energy.

Question 42:  Write two different ways of harnessing energy from the ocean.

Answer 42:

  1. Tidal energy
  2. Ocean Thermal energy conversion

Question 43: What steps would you suggest to minimise environmental pollution caused by the burning of fossil fuels?

Answer 43:

Steps to minimise environmental pollution caused by the burning of fossil fuels are as follows.

  1. Utilise unconventional energy sources like hydrothermal and wind energy.
  2. It is advisable to plant more trees to reduce air pollution.
  3. Use smokeless appliances to cut down on emissions.

Question 44:  What is the role of a plane mirror and a glass sheet in a solar cooker?

Answer 44:

Sunlight is reflected by a plane mirror, intensifying the Sun’s energy. Glass sheet keeps heat from the solar cooker from escaping.

Question 45:  Mention three advantages of a solar cell.

Answer 45:

The three advantages of a solar cell are as follows:

  • The source of renewable energy.
  •  It’s pollution free.
  • Solar panels require little maintenance.

Question 46: What is biomass? What can be done to obtain bio-energy using biomass?

Answer 46:

Biomass is a fuel produced from organic material. The techniques for producing bioenergy from biomass are listed below.

  1. Use firewood as fuel
  2. Cow dung cake can be used for heating purposes.
  3. Production of gobar gas is possible
  4. This gobar gas can be used to produce
  5.  electricity

Question 47:  What are the limitations of obtaining energy from the wind?

Answer 47:

The limitations in obtaining energy from wind

are as follows.

  • Continuous and consistent production is not feasible
  • A large area is required to install a wind power mill.
  • A minimum wind speed of 15 km/hour is required.

Question 48: What is the process used to harness nuclear energy these days? Explain it briefly.

Answer 48:

Nuclear power stations mainly use nuclear energy to generate electricity. It has a turbine, boiler, and nuclear reactor.

  • Nuclear fission is carried out inside the nuclear reactor. Large amounts of energy are produced during nuclear fission.
  • To generate steam, which is needed to boil water, energy from nuclear fission is used.
  • To generate energy, turbines are turned by steam.

Question 49:  How can solar energy be harnessed? Mention any two limitations in using solar energy. How are these limitations overcome?

Answer 49:

Solar Cookers and solar water heaters:

Under the same circumstances, a black surface absorbs more heat than a white or reflecting surface. This property is used in the operation of solar water heaters and solar cookers. Some solar cookers increase the temperature by concentrating the Sun’s rays using mirrors. Glass plates are used to cover solar cookers. The glass sheet reflects the solar energy trapped and causes the food to cook.

Solar Cell

A typical cell produces a voltage of 0.5–1 V and around 0.7 W of electricity when exposed to the Sun. A solar cell panel is a configuration that combines a lot of solar cells and can provide enough electricity for everyday use. The key benefits of solar cells are their lack of moving parts, low maintenance requirements, and ability to operate well without the need for any focusing apparatus. Another benefit is that they can be installed in distant, inhospitable hamlets or incredibly sparsely populated regions where installing a power transmission line may be expensive or unprofitable.

Question 50:  Make a list of conventional and non-conventional sources of energy. Give a brief description of harnessing one non-conventional source of energy.

Answer 50:

Coal, oil, firewood, and tidal energy are examples of conventional energy sources.

Solar energy, nuclear power, biogas, tidal power, ocean thermal power, wave power, and other unconventional sources are some of examples.

Methods to harness Non-conventional sources of energy:

Solar cookers, solar cells, solar water heaters, and solar panels are all examples of solar energy harvesting devices.

Nuclear reactors are used to convert nuclear energy into electrical energy.

The Sun heats the water at the sea or ocean’s surface, whilst the water in its deeper layers is comparatively cool. Ocean-thermal energy conversion facilities use this difference in temperature to generate energy.

Similar techniques can be used to capture the kinetic energy present in large waves that are close to the beach in order to produce power. Strong winds that are blowing across the ocean cause the waves. Only in places where the waves are exceptionally powerful would wave energy be a practical idea.

Question 51:  Why is there a need for harnessing non-conventional sources of energy? How can energy be harnessed from seawater in different ways?

Answer 51:

The following are some of the reasons for the need to harness non-conventional sources of energy.

  1. The use of conventional energy sources will eventually run out because they are an exhaustible resource.
  2. Environmental pollution is not caused by unconventional sources of energy.

Energy can be harnessed from the sea in the following ways:

Tidal energy:

A dam is built across a small sea entrance to capture the energy of the tides. Tidal energy is converted to power via a turbine that is positioned near the dam’s opening. As you know , there are just a few places where such dams can be constructed.

Wave energy

Similar techniques can be used to capture the kinetic energy present in large waves that are close to the beach in order to produce power. Strong winds that are blowing across the ocean cause the waves. Only in places where the waves are exceptionally powerful would wave energy be a practical idea.

Ocean Thermal Energy.

The sun heats the water at the sea or ocean’s surface, whilst the water in its deeper layers is comparatively cool. Ocean-thermal energy conversion facilities use this difference in temperature to generate energy.

Question 52:  What are some of the environmental consequences of using fossil fuels? Suggest the steps to minimise the pollution caused by various sources of energy, including non-conventional sources of energy.

Answer 52:

The following are the environmental consequences of using fossil fuels.

  • Because carbon dioxide levels are rising, there will be global warming.
  • Acid rain is caused by sulphate oxides.
  • Fossil fuel combustion will cause pollution to rise in major cities, which will reduce visibility.
  • Health risks associated with air pollution affect both animals and humans.

Steps to minimise the pollution caused by various sources of energy include non-conventional sources of energy.

  • Maximum use of public transport
  • Most people use vehicles like electric bikes and bicycles to reduce air pollution.
  • Adopting 3R’s policy: reduce, reuse, and recycle.
  • Afforestation

Question 53:  Energy from various sources is considered to have been derived from the Sun. Do you agree? Justify your answer.

Answer 53:

Energy from various sources is considered to have been derived from the Sun. The following are some points to justify the statement.

Because of this, sunlight is indirectly used to generate energy from fossil fuels. Plants capture sunlight to create food, which eventually turns into biomass. Fossil fuels are created from biomass.

  • With the aid of biomass, wood and gobar gas can be obtained.
  • Because of the Sun’s kinetic energy, water on earth is always moving.
  • Water heating causes waves and oceans to form. As a result, the Sun indirectly contributes to the use of geothermal, wave, and tidal energy.

Question 54:  Explain the principle and working of a biogas plant using a labelled schematic diagram.

Answer 54:

In the absence of oxygen, sewage and various plant materials such as crop residue, vegetable waste, and cow dung break down to produce biogas.

The factory has a dome-shaped brick structure. In the mixing tank, cow dung and water are combined to form a slurry that is then fed into the digester. There is no oxygen within the digester, which is a sealed space. The complex molecules in the cow-dung slurry are broken down or decomposed by anaerobic microorganisms, which do not require oxygen. The decomposition process produces gases, including methane, carbon dioxide, hydrogen, and hydrogen sulphide, although it takes a few days to finish. The digester’s gas tank is where the biogas is kept and also where it is drawn through pipes for use.

Given that biogas contains up to 75% methane, it makes a great fuel. It burns without any  trace of pollution, unlike burning wood, charcoal, and coal, which all produce smoke. It has a large heating capacity. Lighting systems also use biogas. Periodically, the remaining slurry is removed and used as excellent manure that is high in nitrogen and phosphorus. In addition to generating energy and manure, the extensive use of bio-waste and sewage material offers a secure and effective means of waste disposal.

Question 55:  What is a good source of energy?

Answer 55:

A good source of energy has the following properties:

  • They are economical
  • They are easy to store and transport
  • They are easily available
  • Work done per unit volume or mass should be large.

Question 56:  What is good fuel?

Answer 56:

When fuel is readily ava ailable, easy to store and transport, burns easily without  ash,  produces a large  quantity of heat energy when burned and has high calorific value , it is said to be good fuel.

Question 57:  What are the disadvantages of fossil fuels?

Answer 57:

Following are the disadvantages of fossil fuels:

  • Fossil fuels like coal and petroleum cause air pollution because they discharge a significant amount of pollutants into the atmosphere.
  • Burning fossil fuels releases gases like carbon dioxide, which contributes to global warming.
  • The carbon, nitrogen, sulphur, and other oxides emitted by fossil fuels have an impact on the fertility of the soil and the quality of potable water.

Question 58:  Why are we looking at alternate sources of energy?

Answer 58:

Fossil fuels are non-renewable sources of energy, meaning they are not readily available in huge quantities   and cannot be replaced; we are looking at other energy sources. If fossil fuel consumption is not restrained, it will run out of supply. It is, therefore, preferable to switch to a different mode of energy source.

Question 59:  How has the traditional use of wind and water energy been modified for our convenience?

Answer 59:

Previously, wind energy was captured and employed by windmills to perform mechanical tasks like lifting or water extraction from wells. But today, electricity is produced by windmills. With the aid of the rotatory motion of the blades, wind kinetic energy is captured and transformed into electricity, turning the turbine of the electric generator to generate power.

In the past, waterfalls served as a source of potential energy. Today, however, water dams are built and employed as a source to capture the potential energy because there are fewer waterfalls. Here, water is poured onto the turbine that generates energy from a set height.

Question 60:  What kind of mirror – concave, convex or plain would be best suited for use in a solar cooker? Why?

Answer 60:

Sunlight serves as both the heating and cooking source for solar cookers. To reflect and concentrate the sunlight in one spot, mirrors are utilised. In a solar cooker, a concave mirror can be utilised since it concentrates all the sunshine at one point, raising the temperature and heating and cooking the food.

Question 61:  What are the limitations of the energy that can be obtained from the ocean?

Answer 61:

The different kinds of energy that can be obtained from the ocean are wave energy, tidal energy, and ocean thermal energy. Following are the limitations of the energy obtained from the ocean:

  • The tidal energy is affected by the relative positions of the earth, Sun, and moon.
  • High dams are necessary to convert tidal energy into power.
  • Strong waves are necessary to generate power from wave energy.
  • The hot surface water and the cold water at a depth should be at least 20°C apart in order to effectively trap ocean thermal energy conversion.

Question 62:  What is geothermal energy?

Answer 62:

The energy that comes from the earth is known as geothermal energy. The hot spots that are created as the molten materials at the earth’s core are forced toward the crust can provide the energy. Geothermal power plants generate electricity using hot springs as a fuel source.

Question 63:  What are the advantages of nuclear energy?

Answer 63:

Following are the advantages of nuclear energy:

  • A large amount of energy is produced per unit of mass.
  • It is clean since it doesn’t emit any pollution.
  • The energy generated by burning 1 atom of carbon is 10 million times greater when 1 atom of uranium is fissioned.

Question 64:  Can any source of energy be pollution-free? Why or why not?

Answer 64:

There is no energy source that is fully pollution-free. However, it is thought that solar cells are pollution-free. However, their production could harm the ecosystem. In the case of nuclear energy, there is no waste left over after fusion. However, the byproducts generated during fission are dangerous. As a result, no energy source is pollution-free.

Question 65:  Hydrogen has been used as rocket fuel. Which is a cleaner fuel: Hydrogen or CNG? Why or why not?

Answer 65:

Considering that CNG contains hydrocarbons, hydrogen gas is cleaner than CNG. In CNG, carbon is a type of contaminant. On the other hand, neither hydrogen nor the fusion of hydrogen creates waste. Consequently, hydrogen is a cleaner fuel than CNG.

Question 66:  Name two energy sources that you would consider to be renewable. Give reasons for your choices.

Answer 66:

Following are the two renewable sources of energy:

  • Wind: The air that is moving quickly is what generates wind energy. Windmills are used to capture wind energy and turn it into power. The earth must be heated unevenly for air to blow. The availability of wind will likewise last eternally since the planet will always be heated.
  • Sun: Solar energy is the energy derived from the Sun. It is created through the continued fusion of helium with other heavy metals and hydrogen. The Sun has an enormous supply of hydrogen and helium that will never run out. Solar energy is a source of energy that can be replenished.

Question 67:  Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.

Answer 67:

Following are the two sources of energy that are exhaustible:

  • Wood: Forests serve as a source of wood. The amount of forests is declining as a result of deforestation. We are aware that a forest grows over many years. The availability of wood will decline as the pace of deforestation rises. Consequently, wood is a finite source of energy.
  • Coal: The dead remnants of plants and animals that were buried for a long time are the source of coal. The demand for coal has skyrocketed due to industrialization, and it cannot be replaced. Consequently, coal is a finite source of energy.

Question 68.

Write the difference between renewable and non-renewable sources of energy. Give one example of each.

Answer 68:

Renewable source of energy Non-renewable source of energy
1. These energy sources are replenishable. These energy sources are not replenishable.
2. It cannot be exhausted after using relentlessly. . It gets easily depleted and takes hundreds of years more to form again.
3. Examples: wind, Sun, tidal energy etc. Example: coal, petroleum, natural gas etc.

Question 69:  Compare and contrast fossil fuels and the Sun as direct sources of energy.

Answer 69:

Since fossil fuels are the leftovers of extinct plants and animals, they are found in the crust of the earth. They are easily accessible compared to coal and petroleum. These energy sources are non-renewable and cannot be replaced.

In contrast, solar energy can be renewed and is abundantly available in nature.

Question 70:  Compare and contrast biomass and hydroelectricity as sources of energy.

Answer 70:

Dead plants and animals are used to create biomass. It is a renewable energy source. Wood and gobar gas are a couple of examples of biomass energy sources.

The potential energy of the stored water at a specific height is used to generate hydroelectricity. In order to generate energy, water is made to fall from a given height onto the generator’s turbines. Hydroelectricity uses dams and reservoirs.

Hydroelectricity and biomass are both sustainable forms of energy.

Question 71:  What is the limitations of extracting energy from:

  1. The wind?
  2. Waves?
  3. Tides?

Answer 71:

  1. a) The wind: Windmills capture wind energy. One of the drawbacks of wind energy is that it can only produce electricity at speeds greater than 15 km/h. Additionally, there will be additional windmills to cover a larger region.
  2. b) Waves: Extremely powerful ocean waves are required to harvest energy from the waves.
  3. c) Tides: The Sun, moon, and earth must be in a straight line, and the tides must be very strong in order to harness the energy tides.

Question 72:  On what basis would you classify energy sources as:

  1. Renewable and non-renewable?
  2. Exhaustible and inexhaustible?

Are the options given in (a) and (b) the same?

Answer 72:

  1. a) Renewable and non-renewable:

Renewable energy sources are those that naturally replenish themselves and are abundantly available  in nature, such as biomass, wind, tidal, and solar energy.

Non-renewable energy sources are those that are scarce in nature and do not naturally replenish themselves. Similar to fossil fuels, which include gas, coal, and oil.

  1. b) Exhaustible and inexhaustible:

Exhaustible energy sources are ones that run out within a few hundred years, like petroleum and coal.

Energy sources that never run out and are abundantly available are said to be inexhaustible. Similar to solar and wind power

Question 73: What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?

Answer 73:


Sunlight serves as the source of heat for the solar cooker. . It is an endless source of pure, renewable energy. It will be affordable due to its endless availability.


It doesn’t work on a cloudy day.

Question 74:  What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?

Answer 74:

More energy is needed as a result of industrialization, and since fossil fuels are easily accessible, they are employed to meet these demands. The environment is affected as a result of their harsh usage. Global warming has been caused by the greenhouse effect, which is the result of overusing fossil fuels.

However, there are limited options for lowering this by minimising the use of fossil fuels and choosing other energy sources. Cut back on any excess water and electricity use. Choose public transport  instead of driving your own car as much. These are a few simple actions that can be taken to lower energy usage.

Benefits of Solving Important Questions Class 10 Science Chapter 14

The basics covered in Class 10 Science will build the foundation for the Class 11 and 12 curricula. Therefore, it is essential that the students practise solving questions from our question bank of Important Questions Class 10 Science Chapter 14 vigorously in order to have a strong conceptual understanding of all the topics which will be covered in the higher classes. Hence, we have provided a set of Chapter 14 Class 10 Science Important Questions for the students to practice the entire syllabus  covered in this chapter. Once they solve it, they will have an in-depth understanding of the topics included in the chapter.

These are some of the benefits students can avail from  NCERT curriculum-based Important Questions Class 10 Science Chapter 14:

  • Students will find questions from different sources compiled in one study material. As a result, they will save time in collecting the questions and their solutions during their preparation.
  • After reviewing the procedures and techniques presented in the latest CBSE curriculum, experienced Science experts created the solutions. A team of professionals reviews and verifies the questions and answers before providing them to the students. So they have complete faith in the resource.
  • Since every question and answer is created with the exam in mind, students are able to approach exams with confidence and overcome exam anxiety.
  • They can also find the key concepts covered in the chapter in the Important Questions Class 10 Science Chapter 14 for revising before they start practising these questions. Thus, covering the chapter from the core to the end and getting themselves ready to get excellent scores. .

Extramarks believes in incorporating the best learning experiences through its own repository. To enjoy the maximum benefit of these resources, students just need to register themselves at Extramarks official website and stay ahead of the competition. Extramarks provides quality resources like NCERT revision notes, CBSE sample papers, CBSE past year question papers,  and mock tests for the students of Classes 1 to 12 and CBSE extra questions. Students can get access to some of these resources by clicking on the link below:

  • NCERT books important questions
  • CBSE Revision Notes
  • CBSE syllabus
  • CBSE sample papers
  • CBSE past years’ question papers
  • Important formulas
  • CBSE extra questions

Q.1 Identify the correct statement among the following.
Statement A: Bulb can be used to test the flow of electric current.
Statement B: Electric current can flow through an open circuit.

A. Only statement A is correct.

B. Only statement B is correct.

C. Both statements A and B are correct.

D. Both statements A and B are wrong.


Only statement A is correct.

Q.2 Vijay and Smita are playing with the wires. They make different shapes out of them. Vijay has two wires of same material and of same length. One of the wires is thick, while the other is thin.

Vijay doubles the length of the thin wire without changing its cross-sectional area.

Smita takes a thick uniform wire of resistance R. She cuts it into three equal parts and joins them in parallel.
(i) Will the current flow in the same ratio in both the wires if they are connected separately with the same source? Give reason for your answer.
(ii) What will happen to the resistance and resistivity of the wire when the length of the thin wire becomes double?
(iii) Calculate the resistance of the parallel combination in terms of the resistance of the original wire.


(i) No, the current will not flow in the same ratio in both the wires if they are connectedseparately with the same source.Resistance (R) is inversely proportional to the area of cross-section (A) of a wire, i.e.,R 1A( area )Therefore, the thicker the wire, more is the area and less is the resistance.Thus, more current will flow easily through the thicker wire of less resistance than thethinner wireofmoreresistance,i.e.,(Ohmslaw).(ii)Resistivityisamaterialproperty.So, itwouldremainsameforspecificmaterial.Resistanceofaconductor,R= LAwhere, =resistivity of the conductorL=lengthoftheconductorA=areaofcrosssectionoftheconductorR L(µ and A are constant)LetRbenewresistancefortwicethelengthofthewire.R 2L(µ and A are constant.)From (1) and (2), we getRR=2LLR=2RThus, the resistance becomes twice the originalresistance.(iii)If L is the original length of the given wire, then resistance of the wire is given as,R= LANow, the wire is cut int o three equalparts.Thus, thelength of each part becomes L/3.The resistance of each of them will be given as,R= L3 A=13 LA=R3Let RE be the equivalent resistance, then1RE=1R/3+1R/3+1R/3=3R+3R+3R=9RRE=R9Equivalent resistance will be one – ninth of the original resistance of the wire.

Q.3 During an activity in the school, the teacher provides a V volt battery each to Navin and Priya and also gives two identical resistors of resistance R to each of them. Navin connects them in series with the battery, while Priya connects them in parallel with the battery. Discuss the heat produced in time ?t? seconds in these two cases.


The equivalent resistance when resistors are connected in series is – R1=R+R=2RHeat produced in time tH1=V22RtThe equivalent resistance when resistors are connected in parallel is –1R2=1R+1R=2RR2=R2Heat produced in time tH2=V2R/2t=2V2tRor,H2=4H1Thus, heat produced in case of parallel connection is 4 times the heat produced in case of seriesconnection.

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FAQs (Frequently Asked Questions)

1. Are the Important questions Class 10 Science Chapter 14 enough to score well in the board exam?

The exercise questions from the textbook are covered in the NCERT Solutions Important Questions Class 10 Science Chapter 14. Students’ questions and clear concepts that are crucial for the tests can be answered by the solutions. In addition to the textbook problems, students can also consult various study guides that provide them with time-saving strategies and techniques for effectively responding to challenging questions.

2. What are the important chapters in the NCERT Class 10 Science?

The NCERT Solutions for Class 10 Science contain  16 chapters, all of which are equally crucial. If students are uncertain about something, they can ask their teachers for clarification or look out for free internet study materials. Students can refer to the solutions at Extramarks to gain a better understanding of the chapters based on the CBSE test pattern.