[Physics Class Notes] on Natural Sources of Energy Pdf for Exam

Energy is one of the most important entities in our universe. We perform many day to day activities. Think, what causes humans to do all the daily activities? This capacity or ability of a body or system to do work is referred to as energy. 

Energy is thus a qualitative property that needs to be transferred to another object in order to make it work or function. Energy can neither be created nor destroyed. It can only be transferred or converted from one form to another. As energy exists in multiple forms, it is hard to find a single elaborate definition of it. Energy can be chemical, thermal, mechanical, electrical, nuclear and light etc. 

The SI unit of energy is Joule (J), which is defined as the energy spent in making an object move through a distance of 1 m, against a supplied force of 1 newton. We will now discuss a few sources of energy in this article below.

Types of Natural Sources of Energy

Energy sources are of two types:

1. Renewable energy sources

2. Non-renewable sources

Renewable Sources of Energy

The sources of energy present on the earth that can get replenished, or recharged without getting exhausted (running out) are called renewable sources of energy. Renewable energy sources are available on a daily or seasonal basis. Renewable sources are clean and do not cause any pollution to the environment. For example: sun, wind and water etc.

The sun is a very essential source of renewable energy in our life. Our sun is a star i.e. its light is internally produced, it does not reflect the light of any other star or body. It is the basic source of heat and light for the entire living world and the source of energy for all ecosystems. Its thermal heat can be used for passively heating buildings and water. Its natural light (daylight) contributes immensely to the reduction of artificial light needed to light our buildings. It is useful for plants to grow. Sun can provide electrical energy with the help of photovoltaic cells (PV Cells), which are made up of silicon or any other material that transforms sunlight into electricity. Solar panels absorb the sunlight and store it in a solar battery. Solar panels convert solar energy into usable electricity by the photovoltaic effect. Solar energy is also used as solar thermal energy.

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Wind energy is an environment friendly and abundantly available source of energy.  Windmills are used to harness the wind potential. Wind rotates the turbine’s blades, which feeds an electric generator and produces electricity. The turbine makes use of kinetic energy of wind and converts it into mechanical energy. The generator can convert mechanical energy into electricity. Mechanical energy can also be used directly for specific tasks such as pumping water etc.

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Water or hydel energy is the energy derived from the flowing water. Electricity produced by the flow of water using dams is called hydroelectricity. In this process, a hydel dam captures energy from the moving water of the river. This water is made to fall from a great height. The falling water rotates the turbine, which feeds the generator. The dam operators control the flow of water and the amount of electricity produced.

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Non-Renewable Sources of Energy

Non-renewable energy sources are those which are present in a limited quantity. They are exhaustible, and will run out if not used judiciously. These sources cause pollution to the environment because carbon is the main element present in fossil fuels such as coal and petroleum. Most sources of non-renewable energy are fossil fuels. Fossil fuels were created as the remains of terrestrial and marine flora and fauna that decayed millions of years ago and got buried in layers under huge amounts of pressure and heat. Most fossil fuels are burnt to produce energy and electricity. Coal is also a fossil fuel.

Fossil fuels are a valuable source of energy. They can also be stored, piped, or shipped anywhere in the world.

Coal is a black coloured rock-like fuel. We burn coal to get energy. Coal is widely used as a domestic fuel to make food. When coal is burnt, it releases harmful smoke. Coal is essentially formed as a result of decayed vegetation. There are four stages in the formation of coal- peat, lignite, bituminous and anthracite. Coal mainly contains carbon, hydrogen and oxygen. 

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Petroleum is a liquid fossil fuel composed of a variety of hydrocarbons. It is a very useful energy source. However, the petroleum that is drilled out from oil wells is crude oil. It has to be refined through a process called fractional distillation, where different hydrocarbons separate to form different fractions. Petrol, kerosene, paraffin, diesel are some of its fractions.  Petrol is used as a fuel in vehicles. Petroleum and its products are used not just for transport but also to manufacture many different products such as plastics, tyres and synthetic materials such as polyester. It is a reliable & portable source of energy. However, the burning of both coal and petroleum is harmful to the environment.

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