CBSE Class 10 Science Sources Of Energy Notes Set E

Download CBSE Class 10 Science Sources Of Energy Study Notes in PDF format. All Revision notes for Class 10 Physics have been designed as per the latest syllabus and updated chapters given in your textbook for Physics in Standard 10. Our teachers have designed these concept notes for the benefit of Grade 10 students. You should use these chapter wise notes for revision on daily basis. These study notes can also be used for learning each chapter and its important and difficult topics or revision just before your exams to help you get better scores in upcoming examinations, You can also use Printable notes for Class 10 Physics for faster revision of difficult topics and get higher rank. After reading these notes also refer to MCQ questions for Class 10 Physics given our website

Sources Of Energy Study Notes Class 10 Physics Revision Notes

Class 10 Physics students should refer to the following concepts and notes for Sources Of Energy Study Notes in standard 10. These exam notes for Grade 10 Physics will be very useful for upcoming class tests and examinations and help you to score good marks

Sources Of Energy Study Notes Notes Class 10 Physics



The ability of a body to do work is called energy. It is measured by the amount of work hat a body can do. It is a scalar quantity and its SI unit is Joule.


A fuel is defined as any substance which burns easily to produce energy. e.g., coal, petrol, kerosene, natural gas,charcoal, wood, etc are fuels. A good fuel is defined as any substance which burns easily to produce adequate amount of heat energy without giving too much undesirable by-products. e.g., petrol, natural gas, LPG, CNG, Biogas, etc are good fuels. In fact, fuels are the concentrated store of energy. The characteristics of a good fuel are:

i. It should produce large amount of useful energy per unit volume or mass.

ii. It should be easily accessible

iii. It should be easy and safe to transport, handle and store.

iv. It should most importantly be economical.

v. It should not produce too much objectionable byproducts like harmful or poisonous gases.

vi. It should have proper ignition temperature.

vii. It should have moderate rate of combustion


Any system from which useful energy can be obtained or tapped is called a source of energy. Any system from which adequate amount of useful energy can be obtained or tapped at a constant rate at a constant rate without giving too much objectionable byproducts is called a good source of energy. The characteristics of a good source of energy are:

i. It should produce large amount of useful energy per unit volume or mass.

ii. It should be easily accessible

iii. It should be easy and safe to transport, handle and store.

iv. It should most importantly be economical.

v. It should not produce too much objectionable byproducts like harmful or poisonous gases.


Fossil fuels are defined as the fuels preserved under the earth’s crust as the remains of plants and animals. They are the rich compounds of carbon which were originally made by the plants with the help of solar energy. Typical examples of fossil fuels are petroleum, coal and natural gas.
Fossil fuels are believed to be formed over millions of years by the burial of plant and animal remains due to unusual sequence of geological processes operating within the earth’s crust. The remains of plants and animals which died millions of years ago were gradually buried deep in the earth and got covered with sediments like sand and mud and were thus locked away from the reach of oxygen. The covers of the sediments prevented their oxidation and decay while the weights of sediments squeezed out water and other volatile materials. In the absence of oxygen and under the continuous combined effect of high pressure, heat and bacteria, these buried remains of plants and animals are converted into fossil fuels like petroleum, coal and natural gas. The buried remains of large plants and animals are believed to form petroleum and natural gas.

Disadvantages of burning fossil fuels:

i. The burning of fossil fuels causes air pollution.

ii. The acidic oxides released on burning fossil fuels cause acid rain, which affects our water and soil resources.

iii. The burning of fossil fuels produces green house gases and hence cause green house effect.

iv. These fuels are non-renewable formed over millions of years.

v. The fossil fuels are limited in nature.

Pollution caused by burning fossil fuels can be reduced as follows:

i. Increasing the efficiency of the combustion process

ii. Using various techniques to reduce the escape of harmful gases and ash to the surroundings. e.g, using electrical precipitators, efficient engines, etc.

iii. Planting more and more trees.

iv. Using ecofriendly renewable sources of energy.

TURBINE: Turbine is a system consisting of a rotor with assembled blades, which are free to rotate. It is used for converting the kinetic energy of a fluid such as flowing water or a gas into the mechanical energy which inturn is used to run the shaft of the dynamo to generate electricity.


Thermal power plant is a power plant in which fuel is burnt to produce heat energy which is then converted nto electrical energy. Large amount of fossil fuel are burnt everyday in power stations to heat up water to produce steam, which further runs turbine to generate electricity. The transmission of electricity is more efficient than Transporting coal or petroleum over same distance, therefore many thermal power plants are set up near coal or oil fields.


Greek words ‘bio’ means living and ‘mass’ means material. Thus, the waste material contained in the bodies of the living organisms like pants and animals is called BIOMASS. When organisms like plants die, their biomass can be used as a fuel for domestic purposes. In fact biomass like wood, agricultural wastes and cowdung together supply about 80% of our domestic energy needs in the rural areas. Wood and some agricultural wastes are also used as a fuel in industries. For e.g. bagasse is used in industrial boilers. Bagasse is the sugarcane from which juice has been extracted. In most our villages, biomass like wood are used as fuel in open furnace called chulhas.

The disadvantages of using biomass as a fuel are:

i. These fuels do not produce much, they have low calorific value.

ii. A lot of smoke is given when they are burnt.

iii. Technological inputs are necessary to improve the efficiency of these fuels.


Burning or heating of a substance in limited supply of oxygen is called destructive distillation.

Charcoal is a form of carbon obtained by the destructive distillation of wood. i.e, by burning wood in the insufficient supply of air. When wood is strongly heated in the insufficient supply of air, the volatile substances present in it are expelled leaving behind a black residue called charcoal. When a solid organic compound is heated in a controlled supply of air, it leaves behind a grey residue commonly called charcoal. Charcoal is used as a fuel in house hold, as a reducing agent and in decolourizing sugarcane juice. It is a good composite fuel.

CBSE Class 10 Physics Sources of Energy Study Notes_1


Charcoal is a better fuel than wood because of the following reasons:

i. Charcoal burns without flame.

ii. Charcoal has high calorific value than wood i.e., Charcoal produces more heat on burning than an equal mass of wood.
For example, 1 gram of charcoal produces 33 kJ of heat energy on burning whereas 1 gram of wood produces only about 17 kJ of heat energy.

iii. Charcoal is a smokeless fuel i.e., it does not produce any smoke while burning and hence does not cause any pollution on doors. On the other hand, burning of wood produces a lot of smoke which pollutes air.

iv. It is a compact fuel and therefore is easy to handle and store and convenient to use than wood.


Biogas is a mixture of gases like methane, carbon dioxide, hydrogen and hydrogen sulphide. The major constituent of biogas is methane gas. In fact, biogas contains about 65% of methane.

Animal and plant wastes are easily degraded by anaerobic microorganisms like anaerobic bacteria in the presence of water to form gases such as methane, CO2, H and H2S. This mixture of gases is called biogas. The process of formation of biogas by the action of anaerobic microorganisms on animal and plant wastes is called fermentation. When obtained from animal dung, then it is called gobar gas and when it is obtained from sewage, it is called sewage gas. This gas can be used for various purposes.

Biogas an ideal fuel and a boon to the farmers: This is because of the following reasons:

i. Biogas is an excellent fuel as it contains upto 75% methane.

ii. It burns without producing any harmful or poisonous gases and smoke.

iii. It has high calorific value (30-40 KJ/g) i.e., it produces more heat on burning.

iv. It has proper ignition temperature i.e., its ignition temperature is neither be too high nor too low.

v. The slurry left behind in the biogas plants is rich in nitrogenous and phosphorous compounds and hence is used as manure by farmers in their fields.

vi. It is also used as a fuel to run engines of water pumping sets required for irrigation.

vii. It has moderate rate of combustion. i.e., it burns smoothly.

viii. It can be used by the farmers for lighting in homes as well as for street lighting in some places.

ix. It is safe to transport, easy to handle and convenient to store. It is supplied by pipes directly from the biogas plant.

x. Biogas plant provides a safe and efficient method of waste disposal.


Biogas plant is a system where biogas is produced on a large scale. A large sized biogas plant which supplies biogas to many houses in a village is called Community Biogas Plant. The cost of installing such a biogas plant is shared by the people in the village community. All the cattle dung from many houses in the villages is used to feed the plant. The biogas is then supplied to all the houses in the village through pipes.

There are two designs of community biogas plants: Fixed Dome Type Biogas Plant and Floating Gas Holder Type Biogas Plant.

Construction And Working Of Fixed Dome Type Biogas Plant:

A fixed dome type biogas plant is a unique type of biogas plant in which a gas holder and the digester are as one single unit and can be constructed by laying bricks. It has a longer life than the floating type biogas plant.

It consists of following parts:

i.. A well shaped underground tank called digester. It is made up of bricks.

ii. A dome shaped roof which acts as a storage tank for biogas. It is also made up of bricks.

iii. A mixing tank connected to the left of the digester through a sloping inlet chamber made of bricks.

iv. An overflow tank connected to the right of the digester through an outlet chamber made of bricks.

v. A Gas outlet at the top of the dome having gas valve ‘V’.

Slurry is made by mixing cattle dung and water in equal proportions in a mixing tank. This slurry is fed into the digester through the inlet chamber. The slurry is left in the digester for 50-60 days in the digester. During this period, anaerobic bacteria and other microorganisms present in the dung carry out its degradation. As a result a mixture of gases called biogas is evolved which begins to collect in the dome. Due to increased pressure of the gas, the spent slurry is forced out through outlet chamber into the overflow tank. This spent slurry is taken out and used as manure because it is rich in Nitrogen and phosphorous compounds. The gas is taken out through the gas outlet and is distributed to the houses through the gas pipes. When pressure falls the fresh slurry is added to the digester and continuous supply of biogas is maintained.

CBSE Class 10 Physics Sources of Energy Study Notes_2

Construction and working of the Floating Gas Holder type biogas plant.

A Floating Gas Holder type biogas plant is a type of biogas plant in which a gas holder and the digester are not as one single unit. It consists of following parts:

i. A well shaped underground tank called digester. It is made up of bricks.

ii. A cylindrical drum shaped gas holder roof which acts as a storage tank for biogas. It is also made up of steel. It floats in the inverted position over the slurry.

iii. A mixing tank connected to the left of the digester through an inlet pipe made of steel.

iv. An overflow tank connected to the right of the digester through an outlet pipe made of steel.

v. A Gas outlet at the top of the gas holder having gas valve ‘V’.

vi. A partition wall which divides the digester into two parts.

The working of Floating Gas Holder type biogas plant is same as the working of fixed dome type biogas plant.

CBSE Class 10 Physics Sources of Energy Study Notes_3


The electricity generated by using the kinetic energy of flowing water in rivers or the potential energy of water stored in a dam is called is called hydroelectricity. The arrangement in which the kinetic energy of flowing water is converted into electricity is called hydro power plant. Hydroelectricity is an indirect source of solar energy.

Principle of generation of Hydroelectricity: in order to produce hydroelectricity, high rise dams are constructed on the river to obstruct the flow of water and thereby collect the water in the reservoirs. The water level rises and in the process kinetic energy of the flowing water gets transformed

into potential energy. The water from the high level is carried through the pipes to the turbine at the bottom of the dam. When the fast flowing water

falls on the turbine, the kinetic energy of the water rotates the turbine rapidly, which in turn rotates the coil of the generator to generate electricity.

Advantages of hydroelectricity:

i. Hydroelectricity is a natural and renewable source of energy and hence we need not to worry about hydroelectric sources getting used up.

ii. It is ecofriendly source of energy if proper precautions are taken while constructing dams.

iii. It is cheap source of energy except for initial investment.

Disadvantages of hydroelectricity:

i. The dams can be constructed only in a limited number of places, preferably in hilly areas.

ii. Large areas of agricultural land and human habitation are to be sacrificed as they get submerged.

iii. Large ecosystems are destroyed when submerged under the water in dams.

iv. The vegetation which is submerged rots under anaerobic conditions and gives rise to large amounts of methane which can cause green house effect.

v. It also creates the problem of satisfactory rehabilitation of displaced people. Opposition to the construction of Tehri dam on the river Ganga and Sardar Sarovar project on the river Narmada are due to such problems.


The moving air is called wind. The kinetic energy associated with the wind is called wind energy. Wind is caused due to unequal heating of the land masses and the water bodies by the solar radiation. The uses of wind energy are:

i. The kinetic energy of the wind can be used to do work. This energy was harnessed by windmills to do mechanical work like to lift water from a ell, to grind grains in flour mills, etc.

ii. It is also used these days to generate electricity with the help of wind mill.

iii. It is also used to run sail boats.

Advantages of wind energy:

i. It is an ecofriendly source of energy.

ii. It is an efficient source of renewable energy.

iii. It requires no recurring expenses for the production of electricity.

Disadvantages of wind energy:

i. Wind energy farms can be established only at those places where wind blows for greater part of a year.

ii. The wind speed should also be higher than 15 km/h to maintain the required speed of the turbine.

iii. Furthermore, there should be some backup facilities like storage cells to take care of the energy needs during a period when there is no wind.

iv. Establishment of wind energy farms requires large areas of land. For a 1 MW generator, the farm needs about 2 hectares of land.

v. The initial coat of establishment of the farm is quite high.

vi. Moreover, since the tower and the blades are exposed to the vagaries of nature like sun, storm and cyclone, they need a high level of maintenance.

Wind mill and wind energy farm:

A windmill is an arrangement which uses wind energy to do mechanical work or to generate electricity. It essentially consists of a structure similar to a large electric fan that is erected at some height on a ground. To generate electricity, the rotatory motion of the windmill is sued to run the turbine of the electric generator. The out put of a single wind mill is quit small and cannot be used for the commercial purposes. Therefore, a number of windmills are erected over a large area to get the energy output on a commercial scale. This arrangement of a number of windmills erected over a large area to get the energy output on a commercial scale is called wind energy farm. Denmark is called country of winds because more than 25% of their electricity is generated through windmills.

CBSE Class 10 Physics Sources of Energy Study Notes_4


The energy radiated by the sun in the form of electromagnetic radiations is called solar energy. It includes light radiations, infra red radiations and ultra violet radiations. Two thirds of solar energy consists of infra red rays. The sun has been radiating an enormous amount of energy at he present rate for nearly 5 billion years and will continue to do so for about 5 billion years more. Only a small part of the solar energy reaches the outer layer of the earth’s atmosphere. Nearly half of it is absorbed while passing through the atmosphere and the rest reaches the earth’s surface.

It is the inexhaustible source of energy. The various functions performed by the sun’s energy on the earth are:

i. Solar energy powers the flow of winds.

ii. It powers the flow of water cycle on earth.

iii. It provides energy for preparing food by the process of photosynthesis by plants and hence sustains life on earth. iv. Sun’s energy created the fossil fuels over a period of millions of years.

iv It provides light and warmth on earth.

v. Nowadays, it is used in devices like solar cookers, solar heaters and solar cells.

 Does all th e energy radi ated b y the sun reach th e earth ’s surface: .

Every square metre of the earth’s upper atmosphere receives 1.4 kJ of energy per second. This is called solar constant. The solar energy reaching unit area at the outer edge of the earth’s atmosphere exposed perpendicularly to the rays of the sun is known as solar constant. It is estimated to be approximately 1.4 KJ/S/m2 or 1.4kw/ m2. But all this energy does not reach the surface of earth. Some of the sunlight is reflected back into space, some is absorbed by water vapour, ozone, dust, CO2 and other gases present in the atmosphere. In fact, only 47% of the sun’s energy that strikes the earth’s atmosphere reaches the earth’s surface and is absorbed. Even this fraction of sun’s energy is quite substantial.


Solar cooker is a solar heating device which uses solar energy for cooking food. It consists of an insulated metal box or wooden box, which is painted black from inner side. Black surface absorbs as well as radiates more heat. The top of the ox is covered by a thick glass sheet so that the radiated heat does not escape from the box. This effect is called green house effect. A mirror adjusted at a suitable angle acts as a reflector so that more and more heat enters the box. The food to be cooked is placed in steel containers painted black from outside. When the solar cooker is kept in the sunlight, the solar energy enters the box and is absorbed by the box. The glass sheet does not allow the radiated heat to escape from the box and as a result the temperature inside the ox rises to about 100oC -150 oC. Thus, the food in the containers gets cooked.

CBSE Class 10 Physics Sources of Energy Study Notes_5

The limitations of solar cooker  :

i. Solar cookers are useful only at certain times during the day.

ii. They cannot be used efficiently on a rainy or foggy day.

iii. They cannot be used during night.

iv. The reflector needs to be adjusted all the time.


Solar cell is a device that converts solar energy into electrical energy. It is also called photovoltaic cell. A typical soar cell develops a voltage of 0.5 to 1 volt and can produce about 0.7 watts of electricity when exposed to sun. Solar cells are made of semi conducting materials like silicon, selenium, germanium, etc with added impurities. The arrangement of a large number of solar cells to deliver energy for practical use is called solar panel.

Advantages of solar cells:

i. They have no moving parts.

ii. They require little maintenance.

iii. They work quite satisfactorily without the use of focusing device.

iv. They can be set up in remote and inaccessible hamlets or very sparsely inhabited areas in which laying of power transmission line may e expensive and not commercially viable.

v. They use a renewable source of energy.

Disadvantages of solar cells

i. Silicon, which is used for making solar cells, is abundant in nature but the availability of the special grade silicon needed for making the solar cells is limited.

ii. The entire process of manufacture is very expensive.

iii. Silver is used for interconnection of cells in the solar panel, which further adds to the cost.


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