CBSE Class 10 Science Notes Chapter 14 Sources of Energy Pdf free download is part of Class 10 Science Notes for Quick Revision. Here we have given NCERT Class 10 Science Notes Chapter 14 Sources of Energy.
CBSE Class 10 Science Notes Chapter 14 Sources of Energy
Need for Energy: The ability of a body to do work is called energy. No activity will occur without energy. So energy is required in all walks of life.
Characteristics of a good source of energy.
- It should be able to do a large amount of work for each unit of mass or volume.
- It should be easily accessible.
- It should be easily transported.
- It should be economical.
Conventional Sources of Energy.
The sources of energy which have been in use since a long time are called conventional sources of energy. For example, Coal, petroleum, natural gas, hydel energy, wind energy and nuclear energy are considered to be the conventional sources of energy. Firewood is also a conventional source of energy but its usage is now limited to kitchens in rural India.
Fossil Fuels.
Coal: Coal was formed millions of years ago. The plants got buried under swamps and due to high pressure and high temperature inside the earth; they were converted into coal. Coal is the highest used energy source in India. During the days of the steam engine, coal was used in steam engines. Moreover, coal was also used as kitchen fuel; before LPG became popular. Nowadays, coal is mainly being used in industries.
Petroleum: Petroleum was also formed millions of years ago. The animals got buried under the ocean surface and were converted into petroleum; in due course of time.
Petroleum is the third major source of energy being used today. Petroleum products are used as automobile fuel and also in the industries. Natural gas mainly comes from the oil wells and is also a major source of energy.
Non-renewable Sources of Energy.
It takes millions of years for the formation of fossil fuels. Since they cannot be replenished in the foreseeable future, they are known as non-renewable sources of energy.
Renewable Sources of Energy.
Those sources of energy which can be replenished quickly are called renewable sources of energy. Hydel energy, wind energy and solar energy are examples of renewable sources of energy.
Hydel Energy: Hydel energy is produced by utilizing the kinetic energy of flowing water. Huge dams are built over a source of water. Water is collected behind the dam and released. When the water falls on the turbine; the turbine moves; because of kinetic energy of water. Thus, electricity is generated by the turbine. Electricity; thus generated is called hydel energy or hydroelectricity.
Limitations of Hydroelectric Plants.
- Dams can be constructed only in a limited number of places, preferably hilly areas.
- Large areas of agricultural land and human habitation get destroyed by the cons¬truction of dams.
- Large eco-systems get submerged under water. The vegetation which is submerged underwater rots under anaerobic conditions and gives rise to large amounts of methane which is a greenhouse gas.
- Rehabilitation of displaced people is another major problem.
Thermal Power Plant: In a thermal power plant, coal or petroleum is used for converting water into steam. The steam is used to rim the turbine; to generate electricity.
Biomass: The material obtained from the bodies of plants and animals is called biomass.
Examples: cattle dung, sewage, crop residue, wood, etc.
Biogas: Biogas is a mixture of methane, carbon dioxide, hydrogen and hydrogen sulphide. It contains 65% of methane gas. Biogas is produced by the anaerobic degradation of bio¬mass in the presence of water but in the absence of air.
Wind Energy: Wind energy has been in use since ages. Windmills have been in use; especially in Holland; since the medieval period. Nowadays, windmills are being used to generate electricity. The kinetic energy of wind is utilized to run the turbines; which generate electricity. At present, Germany is the leading country in terms of wind energy production and India comes at number five. In India, Tamil Nadu is the largest wind energy producing state. The largest wind farm in India is near Kanyakumari; in Tamil Nadu; which generates 380 MW of electricity.
Limitations of Wind Energy: Wind farms can only be established at those places where the wind speed is high enough and is more than 15 km/hr for most parts of the year. Wind farms need to be established on large tracts of land. The fan of the windmill has many moving parts; so the cost of maintenance and repair is quite high. The initial cost of establishing a wind farm is very high.
Non-conventional Sources of Energy: Energy sources which are relatively new are called non-conventional sources of energy, e.g., nuclear power and solar energy.
Solar Energy: The sun is the main source of energy for all living beings on this earth. Even the energy in the fossil fuels has come from the sun. The sun has an endless reservoir of energy which would be available as long as the solar system is in existence. Technologies for harnessing the solar energy have been developed in recent times.
Solar Cooker: Solar cooker is very simple in design and mode of function. It is usually made from mirrors. Plain mirrors are placed inside a rectangular box. The light reflected from the plain mirrors concentrates the solar energy inside the solar cooker which generates enough heat to cook food.
Solar Furnace: Solar furnace is made like a concave mirror. Large solar furnace has many smaller mirrors to compose a very large convex mirror. The thing to be heated is placed near the focus of the mirror.
Solar Cells: Solar cells are made from silicon. The solar panel converts solar energy into electrical energy which is stored in a battery; for later use.
Limitations of Solar Energy: The technologies for harnessing solar energy are at a nascent stage. At present, the cost-benefit ratio for using solar energy is not conducive. Using solar energy is exorbitantly costly.
Tidal Energy: Due to the gravitational pull of the moon, tides happen near seashores. Water rushes up near the seashore during high tide and goes down during low tide. Dams are built near seashores to collect the water which comes during a high tide. When the water runs back to the ocean, the flow of water can be utilized to generate electricity.
Wave Energy: Waves can also be a good source of energy. Many devices are being designed and tested to produce wave energy. For example; a hollow tower is built near the seashore. When water gushes in the tube because of wave, it forces the air upwards. The kinetic energy of air in the tube is used to run a turbine. When the wave goes down; air from up goes down the tube which is also used in running the turbine.
Ocean Thermal Energy: The water at sea surface is hot during the daytime, while the water at a lower level is cold. The temperature differential in water levels can be utilized to generate energy. If the temperature differential is more than 20°C, then ocean thermal energy can be utilized from that place. For this, a volatile liquid; like ammonia; is boiled using the heat from the hot water at the surface. The steam of the volatile liquid is utilized to run the turbine to generate electricity. Colder water from the surface below is utilized to condense ammonia vapour which is then channelized to the surface to repeat the cycle.
Geothermal Energy: Heat energy from molten rocks present inside the earth created under certain favourable conditions by natural processes is called geothermal energy. It is the only type of energy which does not use solar energy.
Nuclear Energy: Nuclear fission is the process during which a bigger nucleus breaks to produce two smaller nuclei. The process generates a huge amount of energy. This phenomenon is utilized in nuclear power plants. Nuclear power is safest for the environment but the risk of damage due to accidental leaks of radiation is pretty high. Further, the storage of nuclear waste is a big problem because of the potential risk of radiation involved.
Advantages of nuclear energy.
- A very large amount of energy can be produced by a nuclear process on using very small amount of nuclear fuel in a nuclear reactor.
- The energy so produced can be easily transformed into electrical energy.
- It does not produce harmful gases.
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