Energy: It is the capacity of doing work. The SI unit of energy is Joule (J).
Principle of Conservation of Energy
The principle of conservation of energy states that energy can neither be created, nor can be destroyed but it can be changed from one form to another form. So, the total energy of a system remains constant.
Sources of Energy: Sources of energy is classified into three types.
- Renewable sources of energy: Those sources of energy that are continuously supplied by nature are called renewable energy. Examples: Sunlight, water, wood, rock etc.
- Non-renewable sources of energy: Those sources of energy that has limited lifespan are called non renewable source of energy. Examples: Kerosene oil, petrol, diesel etc.
- Perpetual Sources of energy: A perpetual resource has a never-ending supply. Some examples of perpetual resources include solar energy, tidal energy, and wind energy.
The second law of thermodynamics or arrow of time always states that in isolated system, entropy always increases. So when we use certain form of energy to do some work, it gets converted into another useless form of energy which can never be utilized for useful purpose. Fr example: When we cook rice, the heat energy supplied will partly used for the thermal agitation of the molecules of the air. So, this results in energy crisis in microscopic scale too. The entropic idea holds in a sensible way here. Eventually this causes energy crisis in large scale.