By | June 11, 2017

Sources of Energy

QUES.1 What are Sources of energy?

Ans. 1  A substance that provides us with energy in the form of heat,light etc. is  known as sources of energy. E.g Coal, petroleum, wood.

Ques.2 State various types of sources of energy. Difference between them?


Renewable Non-Renewable
These are called alternative sources of energy These are conventional sources of energy
Can be renewed on a daily basis. Cannot  be renewed  every now & then
These are in exhaustible These are exhaustible
Will never be finished even after using continuously. Will finish off in another 100 years
E.g solar energy, wind energy E.g Coal, petroleum


Ques.3 What is a good source of energy?


  • Which would do a large amount of work per unit volume.
  • Be easily accessible.
  • Be easy to stored and transport.
  • Should be economical


Ques.4 What is a good fuel?

Ans.4 A good fuel is one which have high calorific value, low medium ignition temperature, easily available, easy to store, not produce harmful substances, not leave residue, cheap.


Ques.5 Which energy would you use for cooking?

Ans.5 Heat Energy


Ques.6 List four forms of energy that you are using in morning when you wake up till you reach the school?


  • Light Energy
  • Heat Energy
  • Mechanical Energy
  • Muscular Energy


Ques.7 What would be your choice of fuel in

  1. A forest


  1. A mountain village or small island.

Firewood and Carbon Cakes

  • New Delhi

LPG, CNG, Wood, Electricity, Petroleum, etc.

  1. When you lived 5 centuries ago.

Firewood and Cow Dung Cakes


Ques.8 Name some conventional sources of energy?


  • Coal
  • Petrol
  • Hydro
  • Wind


Ques.9 How was coal and petroleum formed million years ago?

Ans.9 Coal was formed from large masses of vegetation which got buried under earth crust. Layers of sedimentation took place over the period of time, this increases the temperature and pressure of organic matter and led to the carbonic cation with the result coal was formed. Petroleum was formed in same manner with organic matter from sea.4


Ques.10 What are disadvantages of burning fossil fuels?


  • It leads to air pollution.
  • The oxides of carbon, nitrogen, sulphur that are released on burning fossil fuels are acidic oxides. This leads to acid rain which affects our water and soil resources.
  • It also leads to green house effect.
  • As the amount is less, they would deplete.


Ques.11 Describe the activity which demonstrate the process of thermo- electric production.


In this setup the water in the cooker is heated. It produces steam which through a steam pipe moves the turbine made up of a tennis ball fitted with metal sheets. Then through wire, energy moves to the dynamo from which the bulb is connected in and it starts glowing.


Ques .12 What are different types of power plants? Name the source of energy used by them?


  • Thermal power plant- coal
  • Hydro electrical power plant – moving water
  • Atomic/nuclear power plant- nuclear fuel(uranium)
  • Gas power plant- natural gas.


Ques.13  Draw  schematic diagram of hydro-power plant and explain its working?

Ans.13 Hydro power plant  convert the potential energy of falling water into electricity. In order to produce hydel electricity, high rise dams are constructed on the river to obstruct the flow of the water and the thereby collect water in large reservoirs. The water level rises and in this process the kinetic  energy of flowing water gets transformed into potential energy. The water from the high level in dam is carried through pipes, to the turbines, at the bottom of dam. And water gets filled again by rain.





Ques.14 State the disadvantages of constructing dam?


  • Large areas of agricultural land and human habitation gets submerged.
  • Large eco-systems are destroyed when submerged under water.
  • It creates a green house gas and the submerged vegetation decomposes under anaerobic conditions and produces methane.
  • It creates the problem of rehabilitation of displaced people.


Ques .15 Draw well labelled diagram of bio-gas plant.





Ques.16 What is the composition of bio gas?

Ans. 16

  • Methane- 75% of methane
  • Hydrogen
  • Carbon dioxide
  • Hydrogen Sulphide


Ques.17  What are the substances used for bio-gas?

Ans. 17

  • Cow dung
  • Various plant material
  • Residue after harvesting the crop
  • Vegetable waste
  • Sewage


Ques. 18 Name the bacteria that helps in anaerobic digestion of the material to produce bio-gas.

Ans.18 Methagenous.


Ques.19  State the properties and uses of the bio-gas.

Ans.19  Properties

  • It burns without smoke
  • Leaves no residue like ash or wood
  • Its heating capacity is high
  • It has a low ignition temperature


  • It is used as a household fuel for cooking food
  • Its is used for lighting the street
  • Used for running small machine.
  • The slurry left behind after the production of bio-gas, It is very rich in nitrogen & phosphors and is used by the farmer as manure. So, it is a boon to farmers.


Ques20. How can be the wind captured and used?

Ans. 20 The kinetic energy of the winds can be capture by the wind mills to do mechanical work or to run a generator for electricity production.


Ques.21 Explain the structure & working of wind mill?

Ans21 A wind mill is essentially consists of a structure similar  to a large electric fan that is erected  at same height on a rigid support. To generate electricity the rotatory motion of wind mill is used to turn the turbine of the electric generator. A number of wind mills are constructed over a large area & is called a wind mill farm. The energy output of each windmill in a form, is coupled together to get energy on a commercial large scale.


Ques.22 What is the maximum wind speed for wind mill to work?

Ans.22  The speed of wind should be 15km/h for the working of wind mill & run the turbines to produce electricity.


Ques.23  How much land is required for windmill farm to produce 1 mega watt energy?

Ans.23  2 hectares of the farm is required.


Ques.24  What were the traditional uses of wind mill?


  • To lift water from the wells.
  • To grind cereals to mate flour.


Ques. 25 Why are we looking alternative sources of energy?

Ans. 25

  • To save the conventional sources of energy so that they can last longer.
  • They are generally free of cost so we need to install initially either the solar unit or the wind mills to get electricity.


Ques.26 How has the traditional use of water & wind energy modified for convenience?

Ans.26  In a morning day wind and water energy are used to generate electricity with the help of windmills and hydro electric power station.


 Ques.27 Name some heating devices that run on solar energy?

Ans.27  Solar cooker, solar water heater.


Ques.28  Draw a labelled diagram of solar cooker described? What are advantage, disadvantage its structure & working?

Ans.28 Diagram

A solar cooker is made up of a box which is blackened on the surface and is covered with a glass sheet. The internal side of a lid has plane mirror. Inside box food is cooked is kept the glass is closed, the lid is open and face towards the sun. The solar rays gets reflected in the box and heat up the box creating glass house effect. The temperature of box can go up to 100 degree on a hot day. The food gets cooked with in 5-6 hours.


We get solar energy free of cost & pollution will also get reduce.


It takes a long time to cooked food & solar cooker has to be rotated as sun keeps changing its position. We can’t cook food on cloudy day.


Ques. 29 Name a device that can convert solar energy into electrical energy?

Ans.29  Solar cells & panel can convert solar energy into electric energy.


Ques.30 What is solar cell?

Ans.30  A solar cell is a device which converts solar energy into electrical energy. A typical cell develops a voltage of 0.5.1v and can produce about 0.7w of electricity when exposed to sun. A large number of solar cells are combined in an arrangement called solar cells panel that can deliver enough electricity for practical use.


Ques.31 What are advantages of solar cells?


  • Traffic signals ,toys and calculators are filter with solar cell.
  • They have no moving parts.
  • They require less maintenance.


Ques.32 Name the elements used to make solar cells?

Ans.32 Silicon, germanium and silver Sheets are made of silicon & germanium joined by silver wire.


Ques. 33 What are the application of solar cells?

Ans.33 Artificial satellites and space probes like mars arbiters use solar cells as the main sources of energy. radio or wireless transmission systems in remote location use solar cells. Traffic Signals, calculators and many toys are flitted with solar cells.


Ques.34  Name the energy derived from sea? Explain them.

Ans. Tidal Energy:- Due to the gravitational pull of mainly the moon on the spinning earth, the level of water in the sea rises and falls. This phenomenon is high and low tides and difference in sea-level gives us tidal energy. It is harnessed by constructing a dam across a narrow opening to the sea. A turbine fixed at opening of dams converts tidal energy to electricity.

Wave energy:-  The kinetic energy possessed by huge waves never near the sea shore can be trapped in a similar manner to generate electricity. The waves are generated by strong winds blowing across the sea. Wave energy would be available proposition only where waves are strong. A  wide variety of devices have been developed to trap wave energy for rotation of turbine & production of electricity.

Ocean thermal energy:-  The water at the surface of sea is heated by sun. This difference in temperature is exploited to obtain energy in ocean- thermal energy conversion plants. The warm surface water is used to boil a volatile liquid like ammonia. The vapours are then used to run turbine of generator. The cold water from the depth of ocean is pumped up a condense vapour again to liquid.


Ques.35 What is geo-thermal energy? How can it be used as an energy resources?

Ans.35 Geo thermal energy is generated at the geothermal power plants where the heat of earth is used to generate electricity.

Due to geological changes , molten rocks present in the core of the earth are pushed to the earth’s crust. Steam is generated when the underground water come in contact with these points forming hot springs. This trapped steam is used to generate electricity in the geothermal power plants.


Ques.36 What is nuclear energy ? how is it used to generate electricity in an atomatic/nuclear power plant?

Ans. 36  Nuclear energy is obtained by process of either nuclear fission/nuclear fusion reaction . Nuclear fission is carried out with nuclear of heavy elements like uranium -235, plutonium and thorium and nuclear fusion by light  elements like H2 to form helium in a nuclear power plants, nuclear fuel is used as U-235 which undergoes nuclear fission reaction to produce large amount of heat energy. This heat energy is used  to boil water and get steamed under pressure to run turbine & generator thus producing electricity.


Ques 37 Name the places where we have nuclear power plant?

Ans.37 Tarapur (Maharashtra), kota (Rajastan), kalpakkam(Tamilnadu), Naraura (U.P), Takrapar ( Gujarat), Kaiga( Karnataka).


Ques.38 What are the hazards of nuclear power generative?


  • Storage & disposal of used fuel as it still emits radiation.
  • Improper storage & disposal leads to  environmental contamination.
  • The risk of accidental leakage of nuclear radiation.


Ques39.  Difference between nuclear fission and nuclear fusion reaction?


Nuclear fission Nuclear fusion
a)      It is the break up of nuclear of heavy radio active elements into smaller elements. a)      It is the combination of 2 or more nuclei of  lighter element like H2 to form heavier element like helium
b)      Many harmful radiation are evolved b)      Radiation are not evolved
c)       A large amount of heat energy is released. c)       Energy released is much more.
d)      Can be carried out in a controlled manner. d)      Can’t be controlled once started
e)      E.g fission of U-235 e)      E.g fusion of H2 nuclei to farm helium nuclear.


Leave a Reply

Your email address will not be published. Required fields are marked *