CBSE Source of energy Notes for Class 10 physics

Introduction to Source of Energy

Source of energy is anything which supplies us useful energy for carrying out the various activities like
(i) Heat energy to cook food
(ii) Electrical energy to lighten the room.
(iii) Muscular energy to carry bag and to run bicycle
(iv) Sound energy to call friends.

Renewable and Non-Renewable Source of Energy

Renewable source of energy is the energy source which can be replenished in short period. Example Solar energy, hydropower
An energy source which cannot be recreated in short period is categorized as non-renewable source of energy. Example Fossil Fuel-oil, natural gas, Coal

Good Sources of Energy

A good source of energy has following characteristics:
(i) It could do a large amount of work per unit volume or mass.
(ii) It would be easily accessible.
(iii) it would be easy to store and transport.
(iv) It would be economical.

Conventional and Non -Conventional Source of Energy

Sources of energy which has been in use from Centuries are called the conventional source of energy. Example Wood,Coal,Petrol,hydropower
Source of energy which we have started using in recent times is called Non-conventional energy sources Example Nuclear energy, Geothermal energy, Solar energy, Ocean tides

Fossils Fuels

-Fossils fuel are the remains of the pre-historic animal and plants buried under the earth millions of years
-They are non-renewable sources of energy
- Since fossils fuels from plants and animals and they get energy from Sun, so their ultimate source of energy is Sun
Coal, Petroleum products


A turbine is device that rotates when steam, water or wind false on its blades. The turbine turns the shaft of the electric generator and then electricity is produced

Thermal Power Plants

Thermal power plants burn fossils fuel like coal which heat up the water to produce steam and Steam is used in Turbine to generate electricity.
The term thermal power plant is used since fuel is burnt to produce heat energy which is converted into electrical energy

Hydropower Plants

In hydropower plants,kinetic energy of the flowing water or the potential energy of the water at height is used to turn the turbine and generate electricity.
To produce hydel electricity, high-rise dams are constructed on the river to obstruct the flow of water and thereby collect water in larger reservoirs. The water level rises and in this process the kinetic energy of flowing water gets transformed into potential energy. The water from the high level in the dam is carried through pipes, to the turbine, at the bottom of the dam


Biomass is any organic matter from which we get energy on the renewable basis. It includes wood, Agricultural residues, animal excreta, wastes from food processing.Two important Biomass energy sources are given below


Charcoal is produced by burning wood in an insufficient supply of water. This method is called destructive distillation of wood. Charcoal burns without flames, is comparatively smokeless and has a higher heat generation efficiency


Cow-dung, various plant materials like the residue after harvesting the crops, vegetable waste and sewage are decomposed in the absence of oxygen to give bio-gas. Anaerobic micro-organisms that do not require oxygen decompose or break down complex compounds of the cow-dung slurry. The process is called anaerobic digestion
Since the starting material is mainly cow-dung, it is popularly known as ‘gobar-gas’
Bio-gas contains up to 75% methane,23% Carbon dioxide and 2% other gases. It burns without smoke, leaves no residue like ash in wood, charcoal and coal burning. It is an excellent fuel

Wind Energy and Wind mill

Unequal heating of the landmass and water bodies by solar radiation generates air movement and causes winds to blow. The wind contains the kinetic energy. This kinetic energy is used the windmill to do some mechanical work.
A windmill is a device in which kinetic energy of the wind is used to rotates a set of blades and rotational energy of the blades is used to do some mechanical work and power the turbine to generate electricity

Solar Energy

Solar energy is the energy of Sun. The earth receives a huge amount of energy from the sun. Traditionally We have been solar energy for drying clothes and grains, make salt from sea water

Solar cooker

Solar cooker is a device which is used to cook food by using solar energy. Solar cookers and solar water heaters are based on the facts that A black surface absorbs more heat as compared to a white or a reflecting surface under identical conditions
Solar cooker is having box type structure and its internal surfaces are coloured with black colour. Solar cookers are covered with a glass plate. Which traps heats to go out from box and shows greenhouse effect. A plane mirror is also used to focus the rays of the light. The food which need to be cooked ins kept inside the box and temperature around 140o C in summer in 2-3 hour and cooked the food

Solar cells

A device which converts solar energy into electric energy is called solar cell. A solar cell can convert only 0.7% of the solar energy into electricity. Silicon is used in in creating the solar cells

Solar cell panels

Many solar cells combined in an arrangement is called Solar cell panels. The solar cells in the solar panel are connected in such a that total potential difference and total capacity to provide electric current becomes large

Ocean Energy

Tidal energy

Gravitational pull of the moon on the spinning earth produces tides in the ocean
This phenomenon is called high and low tides and the difference in sea-levels gives us tidal energy. Tidal energy is harnessed by constructing a dam across a narrow opening to the sea. A turbine fixed at the opening of the dam converts tidal energy to electricity

Wave energy

When the wind passes on the water surface, it leads to the pressure difference between upper and bottom wind which results in the generation of waves. This wave energy can be harnessed to power electric generator

Ocean Thermal energy

The water at the surface of the sea or ocean is heated by the Sun while the water in deeper sections is relatively cold. Ocean-thermal-energy conversion plants Exploits this difference in temperature. The warm surface-water is used to boil a volatile liquid like ammonia. The vapors of the liquid are then used to run the turbine of generator. The cold water from the depth of the ocean is pumped up and condense vapour again to liquid

Geothermal Energy

Geo means earth and thermal means heat. So, Geothermal energy is the energy which is obtained from heat inside the earth.
Sometimes molten rocks formed in the deeper hot regions of earth’s crust are pushed upward and trapped in certain regions called ‘hot spots’ and when underground comes in it contact, steam is generated and that steam can be used to power turbine

Nuclear energy

Nuclear energy is generated through the process of Nuclear Fission. In Nuclear fission, A heavy nucleus is bombarded with a low energy neutron. In this process, it splits into two lighter nuclei with a tremendous release of energy which can be utilized to boil water to run turbines.
Nuclear energy is generated in a controlled manner in the Nuclear reactor
The major hazard of nuclear power generation is the storage and disposal of nucleus wastes because they are radioactive
Nuclear FusionNuclear Fusion means joining lighter nuclei to make a heavier nucleus, most commonly hydrogen or hydrogen isotopes to create helium
2H + 2H → 3He (+ n)
It releases a tremendous amount of energy,
The source of energy in the Sun and other stars is also because of Nuclear fusion reaction.

hydrogen bomb

The hydrogen bomb is based on thermonuclear fusion reaction. A nuclear bomb based on the fission of uranium or plutonium is placed at the core of the hydrogen bomb. This nuclear bomb is embedded in a substance which contains deuterium and lithium. When the nuclear bomb (based on fission) is detonated, the temperature of this substance is raised to 107 K in a few microseconds. The high temperature generates sufficient energy for the light nuclei to fuse and a devastating amount of energy is released.

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