Energy |Types & Their sources

What Is Energy ?

Energy is the power behind our world. Although you can’t see it , you can’t do much without it. Whenever things move , light up , change shape , get hotter , or colder or make noises energy is involved.

Stored Energy:

You can do two things with energy : store it or use it. It takes a lot of energy to ride a bike up the hill , but that energy doesn’t disappear. It’s stored by your body and by your bike in a form called potential energy. You use this stored energy when you race back down without pedaling. The potential energy you stored is then converted into kinetic energy (movement energy).


Energy exists in many different forms. Almost everything we do involves changing of energy from one form into another. When we’re using energy , we’re actually converting it into another form

kinetic energy diagram

Kinetic energy

The energy moving things have. Racing cars have lots of kinetic energy.



A kind of kinetic energy carried by invisible waves of electricity and magnetism.


Electromagnetic energy is also carried by radio waves , x-rays , microwaves.



Hot things have energy because their atoms or molecules move more quickly.



Electricity is the convenient form of energy that can be carried along wires



Atoms can release energy from nucleus (central core)



Falling things , like this waterfall , release potential energy stored using gravity

Changing energy:

Heat sensitive photograph , There’s a fixed amount of energy in our universe. We can’t make any more or use any up. All we can do is change energy into other forms. When a car brakes , its kinetic energy doesn’t vanish. It changes to heat in the brakes and wheels

Renewable energy:

Earth has limited amount of fossil fuels such as oil , coal , and gas. Once we’ve used them there will be no more. There are unlimited amounts of renewable energy. This includes energy from the sun , the wind , and the oceans. We can go on using renewable energy forever.


Most of the energy people now use (80%-90%)comes from fossil fuels. The rest comes from renewable energy and nuclear power.

Hydroelectric power:

  • Percentage of current energy use (6%)

  • Reserves left (unlimited)

Rivers flow from mountains and hills down to the sea. This means they release stored potential energy. Hydroelectric power station capture this energy to make electricity.

Fossil Fuels ( energy from coal , oil , gas):

  • Percentage of current energy use – oil 38% , coal 25% , gas 23%.

  • Reserves left – oil 40yrs , gas 100yrs , coal 250yrs.

Although bad for the environment , fossil fuels are still the world’s main energy source. Coal is cheap to make electricity , gas is easy to pipe to homes , and oil is convenient for powering vehicles

Geothermal power (energy from earth's internal heat):

  • Percentage of current energy use – less than 1%.

  • Reserves left – unlimited.

Deep inside , earth is not molten rock. Some of this heat released when volcanoes erupt. Geothermal energy means using earth’s inner heat to generate hot water and electricity.

Bio-fuels (energy made using living plants and animals):

  • Percentage of current energy use – 4%.

  • Reserves left – unlimited.

Growing plants and animals store energy we can use in the future. We can grow crops to make oil or make electricity by burning animal waste such as chicken manure. Energy made this way is called “Bio Fuel”.

Solar energy(energy made from sun's light or heat):

  • Percentage of current energy use – less than 1%.

  • Reserves left – Unlimited.

Almost all the energy from the earth originally comes from the sun. We can tap sun’s energy directly to make an electricity. Solar panels like these turn sunlight into electricity.

Wave power (energy from the oceans and tides):

  • Percentage of current energy use – less than 1%.

  • Reserves left – unlimited.

Wind moving over the oceans stores energy in waves. Waves have kinetic energy (because they move ) and potential energy (because they’re above the normal sea surface). We can use the energy in breaking waves and shifting tides to generate electricity.

Nuclear power ( energy made from atomic reactions)

  • Percentage of current energy used – 6%

  • Reserves left – Raw uranium , 80yrs.

Atoms are made if tiny particles held together by energy. Large atoms can release this energy by splitting apart. Small atoms can release energy by joining together. Most nuclear power stations make electricity by splitting apart large uranium atoms.

Wind power(energy from air currents moving across the earth) :

  • Percentage of current energy use – less than 1%.

  • Reserves left – Unlimited.

Wind turbines work like propellers in reverse. As their rotors spin in the wind , they turn small generators inside and make electricity.

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