Notes
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Topics to be learn : The relationship between work and energy Forms of energy
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Work : When the force is applied on an object, it shows displacement. When an object is displaced due to the force applied on it, work is said to be done
The relationship between the work and the energy :
Energy : The capacity to do work is called energy.
- In the picture the boy is shown playing with a toycar. He uses his muscular force and displaces the car. Thus work is done. He uses his energy for performing this work.
- The boys who run or walk and play on the ground, adults exercising in gym, use their own energy to perform work. Each one has his or her own capacity to do work.
There is energy in every substance in the universe. It is present in non-living things as well as in living things. Energy is the capacity to perform work. We can see the work being done due to energy. The ability is never in the visible form. Thus we cannot see the energy but we can understand and feel it.
Forms of energy :
Mechanical energy, heat energy, light energy, sound energy, chemical energy are the different forms of energy.
Mechanical energy : The energy obtained through the machines is called mechanical energy. Mechanical energy is of two types, viz., potential energy and kinetic energy.
- Potential energy : The energy stored in the object is called potential energy. Potential energy ls stored due to specific state and position of an object.
- Kinetic energy : The energy obtained from the motion of an object is called kinetic energy.
- Example : While playing carrom, to make the coins move, our muscular energy is transferred to the striker. This muscular energy changes the potential energy present in the coins to turn into kinetic energy.
Heat energy : Heat energy is obtained through sunlight. Heat is also produced due to the burning of fuels. The unit of measuring the heat is calories.
- Example : When the convex lens is held in such a way that it helps the sunrays to focus on one point, very soon the smoke is seen arising from this point. The heat energy from the sun is concentrated due to the convex lens and hence the paper starts burning. In this way solar energy is converted into heat energy.
Light energy: Light energy is transformed into food energy by the plants. They perform function of photosynthesis in which sunlight is used in the presence of chlorophyll to synthesise their own starch.
Sound energy : Sound is also a form of energy. Sound can also perform work.
- Example : Glass panes of windows crack due to a loud noise. Sound is used to control the movements of some toy cars.
Chemical energy : The energy obtained through chemical action is called chemical energy.
- The chemical energy is produced through the combustion of fuels.
- Chemical action in the lead batteries produces electrical energy.
- The fire crackers when ignited produce heat, sound, light and chemical energy at the same time.
Electrical energy : Various equipment can work due to electrical energy. Electrical energy is very useful in day-to-day life.
- Electrical energy is used in our houses for various purposes. It is transformed into light energy on lighting a bulb, into kinetic energy on starting a fan, into sound energy while playing a music system, and into heat energy in an oven.
Transformation of energy :
In nature, energy is transformed from one form into other This is called transformation of energy. Sun is the main source of all the forms of energy.
The cycle of energy :
Sun's heat —> Water vapour (Potential energy) —> Vapour condenses and forms clouds —> Rainfall (Kinetic energy) —> Water stored in dams (Potential energy) —> Water released through dam —> (Kinetic energy) —>Falls on turbines (In Hydroelectric power station) —> Kinetic energy —> Electrical energy -> various uses in the house —> light, sound, heat.
Natural chain of transformation of energy :
- Plants prepare food by utilizing solar energy.
- The food produced is in the form of chemical energy.
- This food is consumed by animals.
- They develop muscular energy.
- The digestion of food also produce heat energy in the body.
Energy resources :
- The resources used for obtaining the energy are called energy resources.
The energy resources are classified into two types :
Conventional energy resources or non-renewable energy resources : The energy resources which man has been using for centuries are called conventional energy sources.
- Conventional energy resources are exhaustible and therefore they cannot be replenished back.
- Example : Fossil fuels such as petrol, diesel, natural gas. Wood, coal, etc.
- Wood also cannot be replenished easily.
Non-conventional energy resources or renewable energy resources : The energy resources which can be used again and again and those which are non-exhaustible are called non-conventional energy resources. They were not popular and are not used traditionally,
- Examples: Solar energy, wind energy, tidal energy, hydroelectric energy, energy obtained from oceanic waters, atomic energy.
Solar energy : The energy obtained from the sun.
- This energy is continuous and enormous.
- Solar energy is the root of all forms of energy.
- Solar cooker, solar water heater, solar dryer, solar cell are some equipment that run on solar energy.
- In a solar cell, electrical energy can be obtained from solar energy. Solar electric plants have the capacity to produce electricity on a large scale. A solar plant consists of many solar cells.
Wind energy : Electricity generated by the windmills is called wind energy.
- Windmills work due to strongly blowing winds.
- Windmills are also used to draw water from the wells.
Tidal energy : Electricity generated by the waves of the sea is called tidal energy.
- At a narrow region of the creek, a wall is constructed. The turbine of the generator fitted in a wall rotates due to the waves of high and low tides. These rotations of turbine produce electricity.
Hydel Power or hydroelectricity : Water is stored in the dams at a height. It is brought down by a tunnel and make the turbines rotate. Due to turbines’ rotations electricity is generated.
- The Koyana hydroelectricity project is the biggest one in Maharashtra.
Energy obtained from the oceanic waves : The up and down movements of seawater caused due to waves, can be used to generate electricity.
Atomic energy : The heat liberated during fission of atoms of heavy elements such as uranium and thorium can be used to generate electricity. This energy is called atomic energy or nuclear energy.
Energy saving: Saving energy is as good as generating energy. Saving energy, is of utmost importance because if we waste the energy and try to generate it more and more it leads to severe problems like global warming.
- There are several ways of saving energy such as putting off lamps when not needed, making maximum use of sunlight, etc.
Green energy : The energy resources that do not produce smoke and carbon dioxide and carbon monoxide are called green energy resources. They will also not produce pollution. Therefore such resources are the need of the hour.