Question 1 Suggest two materials that can be used to produce bio - gas. Mention two uses of bio - gas and two advantages of bio - gas plant.
(a) How charcoal is better fuel than wood, why?
(b) How does bio-gas plant help to reduce the problem of pollution? Solution
(a) (i)No flame.
(ii)Charcoal produces more energy.
(i)Name two semiconductors used in solar cell?
(ii)What is solar cell pane?
(iii)State two main advantages of solar panel.
Question 4 Why is not possible to make use of solar cells to meet all our energy needs? State at least three reasons to support your answer.
Question 5 What is bio-gas? Why is bio-gas considered an ideal fuel for domestic use?
(i)What is a wind energy farm?
(ii)Mention the steps involved in generating electricity from such farms.
(iii) State two steps in the process of generation of electricity from a windmill. Solution
The output of a single windmill is quite small and cannot be used for commercial purposes. Therefore, a number of windmills are erected over a large area, which is known as wind energy farm. The energy output of each windmill in a farm is coupled together to get electricity on a commercial scale
The steps involved in production of energy in wind farm are:
(a) The Kinetic energy in the wind turns the turbine blades around the rotor.
(b) Turbine blades rotation power the electric generator. When the rotor turns, it spins the generator to make electricity.
(c) The electrical energy from the generator is transmitted to a substation.
Question 7 What is the importance of hydro power plants in India? Describe how electric energy is generated in such plants.
Question 8 If energy can neither be created nor destroyed, explain with an example as to why we should worry about our energy crisis? Solution
Energy comes in different forms and one form can be converted into another form. For example-if we light a candle, the process is highly exothermic so that the chemical energy in the candle changes into heat energy and light energy on burning. The total energy during a physical and chemical process remains the same but we cannot again put together the heat and light generated along with the products of the reaction to get back the chemical energy in the form of wax. Hence, energy, in the usable form, is dissipated to the suroundings in less usable forms. So the sources of energy we use to do work is consumed and cannot be used again.
Question 9 Draw a well labeled diagram of a biogas plant. Why is slurry left behind considered useful?
Question 10 Mention the transformation of energy that takes place in a thermal power plant. Briefly describe the working of a thermal power plant. Why thermal power plants are set up near oil or coal fields?
Question 11 How is electricity generated in a thermal power plant? Solution
(i) First the coal is burnt into the furnace of steam boiler
(ii) High Pressure steam is produced in the boiler
(iii) This steam is passed through the turbine and Steam force rotates the turbine blades.
(iv) The turbine rotation causes the generator to do its work and create electricity.
(i) Explain with the help of labeled diagram the process of production of biogas in a biogas plant.
(ii) What is biomass?
(i) Differentiate between energy obtained by burning fossil fuels and that obtained as solar energy.
(ii)Name two fossil fuels. Explain how does burning of fossil fuels affect our water and soil resources.
(iii) Name any two gases released on burning of fossil fuels.
Question 14 Compare the advantages of generating energy from bio - mass than getting it from hydro power plant.
Question 15 Write any three disadvantages associated with hydro power plant. Solution
(i) These power stations can be built only where there is huge supply of water
(ii) Constructing a dam is very costly
(iii) It disturbs the neighboring eco-system. It may even destroy inhabited localities near the dam.
Question 16 Define a solar cell. Give any two applications of solar cell. write one factor that makes them commercially viable for transmission of power in inaccessible and remote places.
Question 17 There are upcoming tidal power plants in Gujarat and West Bengal. But tides as a source of energy have not been tapped properly in India.
Question 18 Draw a neat well labeled diagram of a solar cooker. Also write the function of the glass plate.
Question 19 Name three forms in which energy from oceans is made available for us. What are OTEC power plants? How do they operate?
(i) Name three forms in which energy from ocean is made available for use.
(ii) What are the limitations of energy that are obtained from oceans.. Solution
Tidal energy, wave energy, and ocean thermal energy
(i)High dams are required to be built to convert tidal energy into electricity which incurs lot of cost.
(ii) Very strong waves are required, which are not possible all the time.
(iii) Tidal energy depends on the relative positioning of the Earth, moon, and the Sun.
(iv) To harness ocean thermal energy the difference in the temperature of surface hot water and the cold water at depth must be 20șC or more.
(i) Explain the process of nuclear fission. Write the steps involved in generating electricity in a nuclear reactor.
(ii) State any three limitations of harnessing nuclear energy.
(i) Write three advantages and three limitations of using solar cooker.
(ii) State the function of
(a) glass plate
(c) blackened box in a solar cooker.
Question 23 List in tabular form two distinguishing features between renewable and non - renewable sources of energy. Give two examples of each.
Question 24 What are the limitations of extracting energy from
(i) the wind
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