NCERT Notes for Class 10 Science Chapter 14 Sources of Energy

CBSE Class 10 Science notes will assist students in studying the topic thoroughly and clearly.

These CBSE Class 10 Science notes were written by subject experts who made the study material very basic, both in terms of language and format.


Energy is a necessity in our daily existence. There is no action that we can do in our daily lives that does not need the usage of energy.

It has been utilised by the human species in various forms for a long time. Energy cannot be created or destroyed, according to the rule of conservation of energy. However, it can only be changed from one state to another.

Despite this, the world  is experiencing an energy shortage.

The reason for this is that energy gets transformed from usable to unusable forms. As a result, whatever source of energy we use to conduct work is depleted and cannot be replenished.

A source of energy is also any system that may provide energy in a handy form at a consistent pace over a lengthy period of time.

As a result, a good source of energy can be defined by the following characteristics:

  1. It should be able to perform a significant amount of work per unit of volume or mass.
  2. It should be easy to check.
  3. It should be simple to store and move from the point of manufacture to the point of consumption.
  4. It should be cost-effective, i.e. provide more energy for less money.

Conventional Sources of Energy

Conventional energy sources are ones that have been amassed in nature over a lengthy period of time. These resources can’t be replaced fast and will eventually run out. These are also known as non-renewable energy sources.

For eg : petroleum, natural gas, coal and fissionable materials.

Fossil Fuels

There were traces of prehistoric plants and animals that had been buried millions of years ago deep inside the soil. They are called fossil fuels because they are transformed into fuel due to excessive heat and high pressure within the ground.

The energy in fossil fuels is actually solar energy that has been trapped by natural processes over a lengthy period of time. The principal fossil fuels that we use today are coal, petroleum, and natural gas.


It’s a naturally occurring material made up of carbon and carbon compounds that contain hydrogen, nitrogen, oxygen, and sulphur. It is used for heating in both the home and the workplace.


It’s a thick, dark-colored crude oil with a horrible odour. It’s made up of a combination of solid, liquid, and gaseous hydrocarbons, as well as water, salt, and earth particles. It is mostly used in cars and other similar applications.

Natural Gas

It contains methane (CH⁴) ( nearly 97%), propane (C³H⁸) and small amount of ethane (C²H⁶).

Compressed Natural Gas (CNG) is created when liquid natural gas is compressed under high pressure and utilised as a fuel in vehicles such as buses, and trucks and cars.

Disadvantages of Fossil Fuels

The disadvantages of fossil fuels are mentioned below. They are :

  • Air pollution is caused due to burning of fossil fuels.
  • The combustion of fossil fuels produces acidic oxides, which cause acid rain, which has a negative impact on our water and soil resources.
  • CO² ( Carbon dioxide) is one of those greenhouse gasses which is released from the burning of fossil fuels.
  • Fossil fuels are not totally consumed. After they’ve been burned, they leave ashes.

Controlling of Pollution Caused by Fossil Fuels

The pollution created by the burning of fossil fuels can be decreased by improving the combustion process’ efficiency.

Additionally, by employing a variety of ways to decrease the release of toxic gases and ashes into the environment.

In addition to the direct use of fossil fuels for uses such as cooking and transportation, they are mostly used to generate electricity.

Greenhouse Effect

The greenhouse effect is the heating of the atmosphere caused by infrared radiation trapped by CO². The sun is extremely hot and emits short-wavelength infrared light.

The radiation is absorbed by the earth, which then re-emits it. However, because the earth is cooler, it emits longer-wavelength radiation. Certain gases, such as methane, carbon dioxide, and water vapor, absorb these.

The impact is referred to as the greenhouse effect, and the gases are referred to as greenhouse gases. This is what causes the atmosphere to heat up.

Thermal Power Plant

Fossil fuels are burned in this power plant to generate heat energy, which is then transformed into electrical energy. In power plants, fuels are burned to heat water and produce steam.

This, in turn, drives the turbine, which generates power. Electricity transmission is more efficient than coal or petroleum transport over the same distance.

As a result, a large number of thermal power stations are built near coal or oil reserves.

Hydro Power Plant

Hydro power plants are power plants that convert the kinetic energy of flowing water into electricity. Hydroelectricity is the electricity generated by hydropower plants.

Principle of Generating Hydroelectricity

A high-rise dam is built on a river to capture the water flowing through it. It obstructs water flow and collects water in enormous reservoirs as a result.

The kinetic energy of the flowing water is turned into the potential energy of the water held behind the dam in this fashion. The kinetic energy of flowing water is converted from the potential energy of stored water in a dam.

The water from the high level is channeled through pipes to a turbine near the dam’s bottom. The electric generator is connected to this. When the water turbine turns, the generator’s armature rotates swiftly as well, producing energy.

Advantages of Hydroelectricity

The advantages of hydroelectricity are mentioned below :

  • It does not pollute the environment in any way.
  • The moving water required for this purpose is accessible for free.
  • Water is an endless source of energy that will never run out. When it rains, the reservoirs of dams are refilled.
  • The construction of dams on rivers aids in flood control as well as irrigation.

Disadvantages of Hydroelectricity

The disadvantages of hydroelectricity are as follows :

  • Dam construction has the potential to harm the environment.
  • Water submerges a wide range of plants, animals, and their environments.
  • It affects crops by reducing the fertility of the soil in the downstream area.
  • Dams can only be built in a restricted number of locations, particularly in mountainous terrain.
  • Under anaerobic conditions, vegetation that is submerged under water at the dam site decomposes and produces methane (CH⁴), a greenhouse gas.
  • It raises the issue of displaced people’s satisfactory rehabilitation.
  • The blockage or alteration of a river’s path has an impact on the river’s fish and other species.

Improvements in the Technology for Using Conventional Sources of Energy


  1. Bio-mass is the waste material of living organisms, such as cattle manure and the dead parts of plants and animals, that is used as a source of energy.
  2. Wood and cow dung are common biomass fuels in India, however they don’t produce much heat and emit a lot of smoke when burned.
  3. To improve the efficiency of these fuels, technological inputs are required. Cow Dung cake is also used as a fuel for both home and industrial purposes.


  1. It is made by heating the wood in a small amount of air (destructive distillation of wood). Water and volatile compounds in the wood are removed during this process, leaving charcoal (a black substance) as the residue.
  2. Charcoal is a superior fuel than wood since it burns cleanly and produces little smoke. It also generates more heat with less effort.


It’s made up of up to 75% methane, hydrogen sulphide, hydrogen and  carbon dioxide. It’s made when animal waste, such as dung or plane wastes, decomposes in the absence of oxygen. It’s known as gobar gas since the starting ingredient is mostly cow dung.

Bio-gas Plant

Bio-gas plants are the equipment used to manufacture bio-gas. The dome-like construction of this plant is made of bricks. The following are the key components of a biogas plant:

  • Outlet chamber or overflow tank : It’s a drain for the slurry that’s been left behind. Because it is high in nitrogenous chemicals, this slurry is utilised as manure.
  • Mixing tank : Slurry is a mixture of animal dunk  and water that is made in a mixing tank. It is put into the digester from the mixing tank.
  • Gas tank : This gas tank is located close above the digester tank, and bio-gas is taken out through pipes for use.
  • Inlet chamber : It serves as a link between the mixing tank and the digester tank. It has a slope to ensure that the slurry flows smoothly into the digester.
  • Digester tank : It’s a vacuum-sealed chamber with no oxygen. In the presence of water, anaerobic bacteria breakdown or break down complex molecules in the cow-dung slurry, resulting in the formation of biogas. This procedure takes a few days to finish.

Advantages of Bio-gas

The advantages of bio-gas are :

  1. It burns without producing smoke, resulting in reduced pollution.
  2. It is simple to use and does not leave any residue and that’s why it is called clean fuel.
  3. The digester slurry is a good manure that is high in phosphorus and nitrogen.
  4. It provides an excellent means of disposing of waste that might otherwise pollute the environment.
  5. In addition to providing manure and energy, the large-scale use of sewage material and bio-waste provides a safe and efficient means of waste disposal.

Uses of Bio-gas

The uses are :

  1. It is utilised in both home and industrial settings as a cooking fuel.
  2. It’s used to power engines and pumps.
  3. It is used to produce electricity.

Wind Energy

Wind is the term for moving air. Because of its fast speed, the wind has a lot of

energy. Wind kinetic energy is used to perform tasks such as:

  1. Production of electricity.
  2. Pumping out water from the earth with a water-lifting pump.
  3. A windmill’s rotatory motion is used to lift water from a well.


  1. It is a machine that uses the energy of blowing air or wind to operate. It’s a structure that looks like a big electric fan and is placed on a rigid support at a certain height.
  2. When the blades of a windmill are struck by the wind. It has an effect on them. As a result, the windmill’s blades begin to rotate. The blades’ rotational motion can be utilised to power a variety of equipment, including water pumps, flour mills, and electric generators.
  3. A wind turbine is a windmill that generates electricity, while a wind generator is a complete system for generating power using wind energy.

Wind Energy Farm

A huge number of windmills are placed over a vast region for commercial purposes, which is known as a wind energy farm. To generate power on a commercial basis, the energy output of each windmill in a farm is combined.

Advantages of Wind Energy

The advantages are mentioned below :

  1. It is a renewable energy source that is both environmentally friendly and efficient.
  2. The creation of electricity does not necessitate any continuing costs.
  3. It does not pollute the environment.

Limitations of Harnessing Wind Energy

The limitations are :

  1. It can only be established in places where wind blows for the majority of the year.
  2. The minimum wind speed required for a wind generator to function well is 15 km/h, but this is not always the case.
  3. A wind energy plant necessitates a vast amount of land, requiring about 2 hectares for 1 MW of electricity generation.
  4. The cost of establishing a wind energy farm is extremely high.
  5. Because the tower and blades are subjected to the whims of weather, such as sun, rain, cyclones and storms they require a high level of upkeep.

Non-Conventional Sources of Energy

The conventional sources of energy are anticipated to be depleted soon as a result of enhanced technological progress and increased demand.

To meet expanding demand, it’s critical to strike a balance with the limited availability of conventional sources.

It is necessary to investigate alternate or non-conventional energy sources.

Non-conventional sources of energy are those that are continuously produced in nature and are inexhaustible.

These are also known as renewable or alternative sources of energy.

Wind energy,solar energy, hydro energy, bio fuels (such as  bio-gas, wood and alcohol), and ocean hydro energy (tidal energy, ocean thermal energy and sea wave energy) are just a few examples.

The following are some non-conventional or nonconventional sources of  energy:

Solar Energy

The sun’s energy is what we’re talking about. The sun gives us both heat and light. Only about half of the solar energy that falls on the top of the atmosphere (47%) reaches the earth’s surface. The remainder is reflected back into space.

Advantages of Solar Energy

The advantages are as follows :

  • It does not cause environmental pollution.
  • In a hot country like ours, it’s readily available.
  • It is available for free.

Limitations of Solar Energy

There are some limitations of solar energy.

They are :

  1. Because most of the energy reaching the surface is diffused, its direct utility is restricted.
  2. It is not consistently available at all times and in all locations.
  3. On cloudy days and at night, it is not available.

Solar Energy Devices

Solar energy devices are the numerous gadgets that are routinely used to harness the sun’s energy.

Solar cookers, solar cells and solar panels for example.

Solar Cooker

It is a device that uses the energy emitted by the sun to cook food. It consists of an insulated metal box or a black-painted hardwood box on the inside. This is done in order for it to absorb as much sunlight as possible.

A thick glass sheet serves as a lid for the box. A plane mirror is affixed to the box as the reflector. Some solar cookers use concave mirrors to focus the sun’s rays, resulting in a greater temperature.

Advantages of Solar Cooker

They are :

  1. Fuel is saved by solar cookers.
  2. It does not pollute the air.
  3. The nutrients are not damaged because the food is cooked slowly in the solar cooker.
  4. It can cook four different foods at the same time.

Limitations of Solar Cooker

It has some limitations as well. They are discussed below :

  1. On cloudy days and at night, it cannot be used to cook food.
  2. It is not suitable for making chapatis or frying.
  3. To maintain it towards the sun, the direction of the solar cooker must be altered from time to time.

Solar Cell

It’s a device that converts solar energy into electric energy. Silicon is used to make these cells. It has the advantage of being environmentally    friendly and readily available. However, the supply of specific quality silicon for solar cell manufacturing is restricted.

There are no moving parts in solar cells, therefore they are low-maintenance. They don’t require any sort of focusing mechanism to work. This is the primary benefit of solar cells. These are simple to set up in remote and inaccessible locations. Where the cost of installing power transmission lines is prohibitively high and not commercially viable.

Uses of Solar Cells

 Solar cells can be used in various ways. Some of them are mentioned below :

  •   Many scientific and technological applications rely on it.
  • It is used to power artificial satellites and space probes such as Mars orbiters.
  • It is used for street lighting, operating water pumps, traffic signals, etc.
  • It broadcasts radio and television to rural areas.
  • Solar cells can be found in  a variety of toys and calculators.

Solar Panel

A solar panel is an assembly of several solar cells positioned side by side and connected to each other. They’re placed such that the overall potential difference and total capacity to supply electric current are greatly increased.It offers significantly more power for a variety of practical applications. The entire manufacturing process is still prohibitively expensive. Silver is utilised to connect the cells in the panel, which adds to the price.

Energy from the Sea

The sea is a renewable energy source. Sea energy is offered in a variety of forms. These are described as follows:

Tidal Energy

The water level rises and lowers due to the gravitational attraction between the moon and the earth’s sea. As a result, the tides are formed. Tidal energy is the energy possessed by rising and falling water tides.The rising of sea water is referred to as high tide, whereas the falling of sea water is referred to as low tide.

Twice a day, the sea’s tidal waves rise and fall (rise and fall). In coastal places around the world, the massive movement of water between high and low tides provides a huge source of electricity.

Construction of a tidal dam over a tiny passage to the sea can be used to harness tidal energy.

Wave Energy

Very fast sea waves are created when a strong wind blows across the ocean’s surface. They have a lot of kinetic energy as well.Only where there are very strong waves would wave energy be a realistic option. This energy can be used to rotate the generator’s turbine and generate electricity with the help of various gadgets.

Ocean Thermal Energy

The sun heats the water at the sea’s or ocean’s surface, whereas the water in deeper regions is comparatively cool. This temperature difference is used to generate energy and is referred to as ocean thermal energy.

Ocean Thermal Energy Conversion (OTEC) power plants are the equipment that are utilised to harness this type of ocean energy.If the temperature difference between surface water and water at depths of up to 2 km is 293 K (20 °C) or higher, these power plants can operate.A volatile liquid, such as ammonia, is boiled using heated surface water.

The liquid’s vapors are used to power the generator’s turbine. Cold water from the ocean’s depths is used to condense and liquidise vapour.The sea’s energy potential (tidal energy, wave energy, and ocean thermal energy) is substantial, but commercialization is difficult.

Geothermal Energy

Heat from the earth’s interior can be used as a source of energy. This is possible under certain favorable conditions brought about by natural processes. Geothermal energy is the term for this.

Due to geological movements, molten rocks created in the deeper subterranean regions of the earth’s crust are forced higher and stuck in particular areas. These areas are known as hot spots.

Underground water is turned to steam when it comes into contact with these hot areas because of the high heat of molten rocks (magma). They are caught between the rocks and are under a lot of pressure. Turbines attached to electric generators can be powered by this steam.

Although the cost of production would be low, there are only a few commercially feasible areas where such energy may be used. In New Zealand and the United States of America, there are a number of geothermal energy-based power stations in operation.

Nuclear Energy

Nuclear energy is the energy stored in the nucleus of an atom. During a nuclear reaction, It is released. A nuclear reaction occurs when the composition of the responding nuclear changes to generate new elements while simultaneously releasing a huge quantity of energy. Nuclear reactions can occur in two ways:

Nuclear Fission

A heavy nucleus divides into two or more smaller nuclei in this reaction. It is attacked with slow-moving neutrons, resulting in the release of a substantial quantity of energy. The energy produced by the fission of a uranium acorn, for example, is 10 million times that produced by the combustion of a carbon atom from coal.

Such nuclear fuel can be part of a self-sustaining fission chain reaction in a nuclear reactor designed for electric power generation. They discharge energy in a timed manner. Fission reactions yield energy. A modest amount of matter is lost in every fission process. Any nuclear fission reaction converts this lost substance into energy, which is liberated. The energy (E) obtained due to loss of matter of mass (∆m) is given by the famous Einstein’s equation in 1905,

E   = ∆mc²

where     c  =  velocity of light = 3×10⁸ m/s

Nuclear Fusion

Nuclear fusion is a reaction in which two or more lighter nuclei combine to form a heavy nucleus and a huge quantity of energy is released. The following are the conditions for a successful fusion reaction:

  1. High temperature (~4~15 million Kelvin)
  2. High pressure ( ~ 1 million atmosphere)

These processes are known as thermo nuclear reactions because they require a very high temperature.

Fusion of hydrogen nuclei to generate helium nuclei is the source of the sun’s enormous thermal energy.

The sun and other stars get their energy from nuclear fusion processes like this.

Hydrogen Bomb

The thermonuclear fusion reaction is the basis of the hydrogen bomb. The hydrogen bomb’s core is a nuclear bomb based on the fission of uranium or plutonium.This nuclear bomb is encased in a material containing deuterium and lithium.

The temperature of this substance is elevated to 10⁷ K in a few microseconds when a nuclear bomb  (based on fission) is detonated. The high temperature creates enough energy for the light nuclei to fuse, releasing a massive amount of energy.

Hazards of Nuclear Power Generation

The following are the principal risks associated with nuclear power generation:

  1. The continuous decay of radioactive elements such as Uranium into dangerous subatomic particles is a major issue.
  2. Contamination of the environment could result from improper nuclear waste storage and disposal.
  3. Nuclear accidents are also a possibility owing to nuclear radiation leakage.

The use of nuclear energy on a big scale is prohibited due to the aforementioned factors.In India, nuclear power reactors at Tarapur (Maharashtra), Kalpakkam (Tamil Nadu),Rana Pratap Sagar (Rajasthan)  Narora (Uttar Pradesh), Kaiga (Karnataka) and Kakrapar (Gujarat) have installed capacities of less than 3% of the country’s total energy producing capacity.Nuclear reactors, on the other hand, provide more than 30% of electric power in several industrialised countries.

Environmental Consequences

We’ve seen how exploitation of any energy source devastates the environment and its delicate equilibrium. However, as compared to fossil fuels, the degree of damage caused by non-conventional energy sources is quite low.

As a result, it is the moral responsibility of every common man on the planet to seek out the cleanest available energy sources. The following are the environmental consequences of rising energy demand:

  1. Acid rain is produced by the combustion of fossil fuels, which harms plants (crops), soil, and aquatic life.
  2. The release of greenhouse gases such as carbon dioxide into the atmosphere is growing as a result of the burning of fossil fuels.
  3. Deforestation (the removal of trees from the forest for the purpose of getting firewood) causes soil erosion and the extinction of species.
  4. Hydropower plant building is disrupting the ecological balance.
  5. Radioactivity in the environment is increasing as a result of nuclear power plants.
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