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ScienceClass 10CBSE

1.      How can solar energy be harnessed? Mention any two limitations in using solar energy. How are these limitations overcome?

Solar Cookers and solar water heaters: A black surface absorbs more heat as compared to a white or a reflecting surface under identical conditions. Solar cookers (Fig. 14.6) and solar water heaters use this property in their working. Some solar cookers achieve a higher temperature by using mirrors to focus the rays of the Sun. Solar cookers are covered with a glass plate. Solar energy trapped is reflected by the glass sheet which make the food cook. Solar Cell A typical cell develops a voltage of 0.5–1 V and can produce about 0.7 W of electricity when exposed to the Sun. A large number of solar cells are, combined in an arrangement called solar cell panel (Fig. 14.7) that can deliver enough electricity for practical use. The principal advantages associated with solar cells are that they have no moving parts, require little maintenance and work quite satisfactorily without the use of any focussing device. Another advantage is that they can be set up in remote and inaccessible hamlets or very sparsely inhabited areas in which laying of a power transmission line may be expensive and not commercially viable.

ScienceClass 10CBSE

What is biomass? What can be done to obtain bio-energy using biomass?

Fuel obtained from organic material is called biomass. Following are the methods to obtain bio-energy using biomass. Using firewood as a fuel Preparing cowdung cake and use them as heating source Gobar gas can be produced Electricity can be produced by using gobar .

ScienceClass 10CBSE

1.      What are the limitations in obtaining energy from wind?

Limitations in obtaining energy from wind. There will not be continuous and consistent production Area required to install wind power mill is Minimum speed of the wind should be 15 km/hour.

ScienceClass 10CBSE

1.      Mention three advantages of a solar cell?

Advantages of a solar cell is as follows. Solar cells are the source of renewable energy Solar cells do not produce pollution Solar cells need minimum maintenance

ScienceClass 10CBSE

1.      Write two different ways of harnessing energy from ocean.

Tidal energy Ocean Thermal energy

ScienceClass 10CBSE

1.      What is the role of a plane mirror and a glass sheet in a solar cooker?

Soln: Plane mirror reflect the sunlight thereby increasing the intensity of solar energy. Glass sheet prevents heat escape from solar cooker.

ScienceClass 10CBSE

1. What steps would you suggest to minimise environmental pollution caused by burning of fossil fuels?

Steps to minimise environmental pollution caused by burning of fossil fuels are as follows. Use con-conventional sources of energy such as hydrothermal and wind Afforestion should be adopted to control air pollution Smokeless appliances should be used to reduce the pollution

ScienceClass 10CBSE

1.      Why is there a need to harness non-conventional sources of energy? Give two main reasons.

Following are the reason for the need to harness non-conventional sources of energy. Conventional sources are exhaustible source of energy and they will get exhausted in the near Non-conventional source of energy did not lead to environmental

ScienceClass 10CBSE

1. Choose the incorrect statement (a) We are encouraged to plant more trees so as to ensure clean environment and also provide bio-mass fuel (b) Gobar-gas is produced when crops, vegetable wastes etc., decompose in the absence of oxygen (c) The main ingredient of bio-gas is ethane and it gives a lot of smoke and also produces a lot of residual ash Bio-mass is a renewable source of energy

Soln: Answer is (c) The main ingredient of bio-gas is ethane and it gives a lot of smoke and also produces a lot of residual ash Explanation: Main product of a biogas is methane. It burns with less smoke and did not produce residual ash.

ScienceClass 10CBSE

1. Choose the incorrect statement regarding wind power (a) It is expected to harness wind power to minimum in open space (b) The potential energy content of wind blowing at high altitudes is the source of wind power (c) Wind hitting at the blades of a windmill causes them to rotate The rotation thus achieved can be utilised further (d) One possible method of utilising the energy of rotational motion of the blades of a windmill is to run the turbine of an electric generator

Answer is (b) The potential energy content of wind blowing at high altitudes is the source of wind power. Explanation: Wind power runs by kinetic energy of the wind. Hence statement b) is wrong.

ScienceClass 10CBSE

1. In a hydroelectric power plant more electrical power can be generated if water falls from a greater height because (a) its temperature increases (b) larger amount of potential energy is converted into kinetic energy (c) the electricity content of water increases with height more water molecules dissociate into ions

Soln: Answer is (b) larger amount of potential energy is converted into kinetic energy

ScienceClass 10CBSE

1. Choose the correct statement (a) Sun can be taken as an inexhaustible source of energy (b) There is infinite storage of fossil fuel inside the earth (c) Hydro and wind energy plants are non polluting sources of energy Waste from a nuclear power plant can be easily disposed off

Soln: Answer is (a) Sun can be taken as an inexhaustible source of energy Explanation: Fossil fuel is an exhaustible source. Hydro and wind energy plants can have large environmental impacts by changing the environment and affecting land use, homes, and natural habitats in the dam area. Disposing off waste from a nuclear power plant is the major issue faced by nuclear plant.

ScienceClass 10CBSE

1. The power generated in a windmill (a) is more in rainy season since damp air would mean more air mass hitting the blades (b) depends on the height of the tower (c) depends on wind velocity can be increased by planting tall trees close to the tower

Soln: Answer is (c) depends on wind velocity Explanation: High wind velocity will turn the turbine with at higher speed. This will increase the production of electricity.

ScienceClass 10CBSE

1. The main constituent of biogas is (a) methane (b) carbon dioxide hydrogen (d) hydrogen sulphide

Soln: Answer is (a) methane Explanation: Methane gas is the main product of biogas. Around 70% of the gas produced is methane and remaining will be ammonia, carbon-di-oxide.

ScienceClass 10CBSE

1. Which part of the solar cooker is responsible for green house effect? (a) Coating with black colour inside the box (b) Mirror (c) Glass sheet Outer cover of the solar cooker

Soln: Answer is (c) Glass sheet Explanation: Green house effect is due the trapping of heat by the atmosphere. Heat is produced is due to presence of green house gases like CO2, SO2. In Solar cooker same thing happens. Solar energy trapped is reflected by the glass sheet which make the food cook.

ScienceClass 10CBSE

1. The major problem in harnessing nuclear energy is how to (a) split nuclei? (b) sustain the reaction? (c) dispose off spent fuel safely? (d) convert nuclear energy into electrical energy?

Soln: Answer is (c) dispose off spent fuel safely? Explanation: Nuclear plants produces highly radioactive material. This if released to the environment they pose major threat to living organisms. Hence, disposing the spent fuel safely is a major problem in harnessing nuclear energy.

ScienceClass 10CBSE

1. Ocean thermal energy is due to (a) energy stored by waves in the ocean (b) temperature difference at different levels in the ocean (c) pressure difference at different levels in the ocean tides arising out in the ocean

Answer is (b) temperature difference at different levels in the ocean Explanation: Energy from surface is used to boil volatile liquid. Vapors from these are utilized to turn the turbine.

ScienceClass 10CBSE

1. Which one of the following forms of energy leads to least environmental pollution in the process of its harnessing and utilisation? (a) Nuclear energy (b) Thermal energy (c) Solar energy Geothermal energy

Answer is (c) Solar energy Explanation: In nuclear energy metals like uranium are used which releases harmful rays than can affect the living organisms. In Thermal energy coal is used which releases Sulphur and Carbon-di-oxide and causes air pollution. In the case of geothermal energy the energy is absorbed by the pressure by the heat from the core which can sometimes be extremely hot and dangerous.

ScienceClass 10CBSE

1. Which is the ultimate source of energy? (a) Water (b) Sun (c) Uranium Fossil fuels

Soln: Answer is (b) Sun Explanation: Plants produce food by using solar energy. Fossil fuels are produced from dead plants. Hence Sunlight is the source of all energy either directly or indirectly.

ScienceClass 10CBSE

1. In a hydro power plant (a) Potential energy possessed by stored water is converted into electricity (b) Kinetic energy possessed by stored water is converted into potential energy (c) Electricity is extracted from water Water is converted into steam to produce electricity

Soln: Answer is (a) Potential energy possessed by stored water is converted into electricity . Explanation: Water stored in dams possess potential energy. When it is released it possess potential energy which is used to turn the turbines. Turbines produces electricity.

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