Unit-3 | ENERGY | Class-10

Overview: Energy is the capacity to do work. Energy can neither be created nor destroyed but can be transformed from one form to another. Here, we will cover about energy, its sources, and types.



Energy:

Energy is the capacity to do work. Its SI unit is Joule (J) and C.G.S. unit is erg. 

Sources of Energy:

All that which can provide enough useful energy at a steady rate are called sources of energy. 

On the basis of the form in which energy sources are used, sources of energy are categorized into two types:

  • Primary energy sources:

Primary energy sources are the sources of energy found in nature and can be used without any human engineered conversion process. In general words, those energy sources which can be used directly in the form that they are found in the nature are called primary energy sources. Example: coal, wood, crude oil, solar energy, wind energy, etc.




We all know, we need not process the solar energy any further to be able to use it. We can directly use the rays of the sun as the solar energy. Thus, solar energy is the primary energy source. 

  • Secondary energy sources:


Secondary energy sources are the sources of energy that are derived from the primary energy sources and need engineered conversion process. In general words, those energy sources are extracted from the primary energy sources. Example: wood-gas, coke, petrol-diesel, bio-gas, hydroelectricity, wind energy, nuclear energy, etc.

We all know, petroleum (gasoline) is extracted from crude oil which is primary energy source so, we can say that petroleum is derived/ extracted from primary energy source. So, petroleum (gasoline) is a secondary source of energy.
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Classification of Sources of Energy on the basis of Replacing Period:

  • Non-renewable sources of energy
  • Renewable sources of energy

Non-renewable sources of energy:

All the sources of energy that are limited in nature and are exhaustible are called non-renewable sources of energy. They cannot be replaced once they have been used up. If they are exhausted then, they take millions of years to regain. 
Example are: fossil fuels, petroleum, coal, etc.

Renewable sources of energy:

All the sources of energy that are abundant in nature and are inexhaustible are called renewable sources of energy. They can be replaced once they have been used up. They can be regained within a short period of time.
Example are: solar energy, wind energy, hydro energy, etc.

Some non-renewable sources of energy:

Fossil fuels:

Fossil fuels are the dead remains of ancient plants and animals found inside the earth which got buried deep due to some natural processes. These are used as sources of energy at present. Following are the major fossil fuels:
  • Coal

It is the most abundant fossil fuel on Earth. The formation of coal takes very long time because it is a fossil fuel. Coal is formed when dead plants are buried inside the Earth over millions of years. Because of very high temperature and pressure, the physical and chemical properties of these plants suffered continuous changes and finally, they changed into a solid material, called coal.

  • Petroleum
Petroleum is a mixture of different types of hydrocarbons. The different types of petroleum products are diesel, petrol, jet fuel, kerosene, etc.

#Question: Why are petroleum used more than other sources of energies?

  • Natural gas
Natural gas is the cleanest burning fossil fuel.



Some renewable sources of energy:

  • Hydropower: The mass production of electricity by the use of kinetic energy generated from continuous flow of water is called hydroelectricity.

  • Biomass and Bio-energy: Biomass is organic material that comes from plants and animals. Bio-energy refers to the electricity and gas produced from the organic material called biomass.

  • Wind energy: The electrical energy generated by the use of kinetic energy (generated by the moving of turbines and windmills) of the wind is called wind energy.

  • Tidal energy: The energy derived from the rising and falling ocean tides is called tidal energy.

  • Geothermal energy: Geothermal energy is the thermal energy generated and stored in the Earth.

  • Nuclear energy: The energy generated from the nucleus of an atom either by dividing (fission) or by joining (fusion) is called nuclear energy.

  • Solar energy: The energy derived from the sun is called solar energy.

 Sun: The Ultimate Source of Energy;
Solar energy is the energy that is derived from the rays of the sun. Sun is said to be the ultimate source of energy because every other energies we have dealt in this lesson so far are directly or indirectly the result of solar energy. Hydroelectricity generated from the rotation of turbines with the K.E. of the water is indirectly the result of the solar energy. Evaporation of water in the seas, oceans and other water sources condenses in the air and forms clouds and the water flows in the rivers which in turn produces hydroelectricity. Fossils fuels which are the dead remains of the plants and animals are only generated when the survival of plants and animals were possible. Plants prepare food using light energy and animals depend upon plants for survival. Meaning that, both are depended upon the light energy i.e. Sun. Wind is caused due to the difference in atmospheric pressure which is the result of the Sun. So, in the same manner, all other energies are also directly or indirectly depended upon the sun (solar energy) and therefore, the sun is called the ultimate source of energy.

 Energy crisis:

The excessive use of non-renewable sources of energy causes the scarcity of energy sources which is called energy crisis.

Measures to solve the problem of energy crisis:
  • Promote the use of renewable sources of energy.
  • Use the alternative sources of energy as far as possible.
  • Do not misuse the sources of energy at any place. 

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#Questions:
  • What is energy and why is sun called the ultimate source of energy?
  • Differentiate between renewable and non-renewable sources of energy.
  • State the various types of renewable sources of energy.
  • What is energy crisis and write the methods to solve it.



This much notes would be enough for this chapter. This is one of the easiest chapter from Physics in class 10.

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