We do lots of work in a day.
To lift up heavy things, to push objects, for writing, cooking
our body requires specific capacity. The capacity to do
certain work is called energy.
Energy is required to do any sort of work.
Similarly Plants, animals, vehicles and machines requires
energy to work.
Energy is available in environment in different forms.
Solar energy is the main source of energy.
It gets converted in different forms of energy.
Different forms of energy can be changed
from one form to another.
• The energy from the sun is absorbed by animals and
plants. They are nourished by the sun’s energy. Solar
energy gets stored in their bodies in their bodies in
the form of chemical energy.
• A long time ago, remnants of
plants and animals got buried
into the earth. Due to the effect
of the tremendous pressure of
the layers of earth above and the
heat inside they were converted
into fuels.The energy left behind
was in the form of hydrocarbon
compounds. So these remains
were converted into fuels. Such
fuels are called fossil fuels. It
takes of lakh of years for such
fuels to be formed and hence the
stores of fossil fuel are limited.
Types of Fossil Fuels
• Fossil fuels are found in three forms – Solid, Liquid as
well as gaseous.
Solid Coal From the remains of plants
Liquid Mineral Oil Marine plants and animals
Gaseous Natural Gas Marine plants and animals
• Wood, charcoal, cowdung pats are solid fuels.
• Convenience– Easily available, cheap.
• Limitation – Less combustible, Creates pollution via
burning.,destruction of forests, has endangered the
environment . Burning of cowdung pats destroys
nitrogen contents. Charcoal is formed when wood is
burnt in insufficient air. Charcoal burns amokelessly.
• Mineral oil is found nearly 25,000 metres deep in the
bowels of the earth. Petrol, diesel, kerosene and fuel
oil can be obtained from it.
• Convenience: Causes less pollution as compared ti
highly combustible solid fuel.
• Limitation: Polluting gases are generated.
Inconvenient for motor vehicles.
• Methane, ethane, propane, butane, etc are the
various types of natural gas.
• The gas filled in cylinder which we use for cooking is
• Convenience: Very convenient fuel to use, lights up
quickly, doesn’t leave behind any solid substance
after burning. Easy to transport from it’s main source
by means of pipes. Burning and use of natural gas
can be easily controlled. It’s burning doesn’t produce
Increasing use of energy
• Because of increasing population, industrialisation
use of energy has increased.
• The deposits of fossils and other fuels is limited and
hence they cannot be permanent sources of energy.
• Hence it is necessary to search for alternate sources
Conventional sources of energy -
• Carbon dioxide emitted is causing a rise in global
• Gases release in the atmosphere have given rise to
dangers like acid rain.
• Holes in the ozone layer of the atmosphere are
allowing the passage of harmful rays.
• Unrestricted cutting down of trees has caused
degradation of forests.
Because of all these reasons the need for
alternate source of energy has aroused.
Non-conventional or Renewable sources
• Earlier sources of energy like wind energy, hydro-
electric energy, biogas, biodiesel, energy generated
through sea water were not used often .So these are
called as non-conventional energy sources.
• Even though they are used again and again energy
gets generated in some time. Also the energy source
doesn’t get depleted and hence is unlimited. And
hence they are called renewable sources of energy.
• Solar Cooker, Solar heater, Solar Cell, are some of
the devices running on solar energy.
Use of Atomic energy - Option for
depleting energy sources.
• Uranium atoms are bombarded with neutrons to
obtain atomic energy.
• At Tarapur in Maharashtra and at Kakrapur in
Surat(Gujrat) governmet has set up atomic centres.
Government’s plan to meet the energy
• Finding out new sources of energy
• Giving preference to renewable sources of energy.
• Using non-renewable sources of energy responsibly
and sparingly. Educating the public about these
• Promoting the use of devices that consume less fuel.