Class 9th
Physics
Chapter 06
Work And Energy (Efficiency)
-
Energy:
Energy is ability of matter to do work . Every matter in this universe needs energy to work.
-
Sources of Energy:
There are energy transformation technologies which convert energy from some source into useful form of energy. The raw material obtained from nature which gives energy to be converted to useful form is known as Energy resource.
The following are the major sources of energy:
-
Renewable and Non-renewable resources:
Energy resources can be divided into two categories.
-
Renewable Resources:
If an energy resource renews itself in normal human life span it is said to be Renewable source of energy. e.g Energy from Bio-mass , Wind energy, Solar energy.
-
Non-renewable Resources:
If an energy resource doesn’t renew itself in Normal human life span it is said to be Non-renewable resource. e.g Energy from Oil , Coal , Natural Gas etc.
-
Important sources of energy:
Some of the major Sources of energy are given below,
A) Fossil fuels :
Fossil fuels are actually the remains of million-year old life existing on earth. Old plant life -now coal and Aquatic animal life – now gasoline and Natural gas.
1. Coal:
Coal is the most abundant fossil fuel on this earth . It has estimated reserves of One million metric tons. Burning coal for producing energy results significant amount of aur pollution.
2. Oil:
We can refine crude oil into different energy products such as gasoline, jet fuel , heating oil , kerosene oil ,petrol, diesel and Greese etc. Oil has limited reserves in the world it is a preferred source of energy over coal because it produces more energy as compared to same amount of Coal.
3. Natural Gas:
Natural gas is a by product of crude oil, it is a mixture of gases. The most common gas present in natural gas is methane CH4. The benefit of natural gas is that it is easy to transport over Larger distances. The amount of pollution by Natural gas is way less than that of crude oil and coal.
B) Bio-mass:
Bio means life, so Bio-mass is energy from living things. Biomass me material from which we get bio energy. Biomass is produced when plant matter (carbohydrates) convert Solar energy by the process of photosynthesis. The simplest process of obtaining biomass energy is eating. When we eat a fruit vegetable or a process to virtual of either we are taking advantage of the energy stored as biomass.
C) Geothermal Energy:
Energy recoverd from core of earth is known as Geothermal energy. This energy in the core of earth is result of energy trapped in the core of earth during formation of planet 5 billion years ago. It is used to generate Electrical energy in many parts of world.
D) Wind energy:
When wind blows it has kinetic energy. This kinetic energy is used in many parts of world to generate electricity. It is environmental friendly because it doesn’t produce pollution. But problem is that it requires very large amount of space. It also produce noise pollution so should be away from the populated area.
E) Nucleur energy:
The energy obtained from nucleus of atom is known as Nuclear energy. There are two processes of producing energy from nucleus of atom.
Nucleur Fission is the process of splitting up of a heavy nucleus like Uranium into two(Barium and Krypton )or more nuclei. This splitting produces enormous amount of nuclear energy.
Nucleur Fusion is the process of obtaining a heavy nucleus from two or more small nuclei. This also produces enormous amount of nucleur energy.
F. Solar Energy:
This energy is known as Radiant Energy.The energy directly obtained from sunlight can be used to produce electricity. Solar cells convert Solar energy directly into electrical energy. Sunlight is the only fuel of Solar cells . It is 100% free and eco friendly. However just like wind energy significant land area is required to produce large amount of energy.
G) Hydroelectric Generation:
Electrical energy obtained from the gravitational potential energy of water is known as Hydroelectric generation. Water is lifted to a height it obtains a significant amount of gravitational potential energy. When it is dropped from height it gains Kinetic energy. When water falls on turbines It gives it Kinetic energy to the turbine and it starts rotating. A generator is connected to the Turbine which converts kinetic energy of turbine to electrical energy. This is totally a free energy resource but it costs too much on setting a hydal power plant. That is why only 20% electrical energy is obtained from this source in Pakistan.
