Multiple Choice Questions
Question 1. Which of the following is a non-renewable source of energy?
(c) Fossil fuels
Explanation: Sources of energy which are present in limited amount and can’t be recycled once used are known as non-renewable sources of energy. Fossil fuels are non-renewable source of energy.
Question 2. Acid rain happens because
(a) sun leads to heating of upper layer of atmosphere
(b) burning of fossil fuels release oxides of carbon, nitrogen and sulphur in the atmosphere
(c) electrical charges are produced due to friction amongst clouds
(d) the earth atmosphere contains acids
Explanation: The oxides of carbon, nitrogen and sulphur that are released by burning fossil fuels form acidic oxides. These lead to acid rain which affects our water and soil resources.
Question 3. Fuel used in thermal power plants is
(d) Fossil fuels
Explanation: Large amount of fossil fuels are burnt every day in power stations to heat up water to produce steam which further runs the turbine to generate electricity.
Question 4. 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
(d) water is converted into steam to produce electricity
Explanation: The water stored in dams has potential energy associated with it. Potential energy possessed by stored water is converted into electricity
Question 5. Which is the ultimate source of energy?
(d) Fossil fuels
Explanation: Sun is the ultimate source of energy as many of the sources (like wind energy etc) ultimately derive their energy from the Sun.
Question 6. 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
(d) Geothermal energy
Explanation: Solar energy leads to least environmental pollution in the process of its harnessing and utilization.
In case of nuclear energy, the major concerns of pollution are while storage and disposal of spent fuels where there is always a risk of leakage of radiation.
In case of thermal energy, enormous amount of air pollution is produced.
Even in case of geothermal energy a little amount of pollution is produced.
Question 7. Ocean thermal energy is due to
(a) energy stored by waves in the ocean
(b) temperature difference at different levels in the ocean
(c) pessure difference at different levels in the ocean
(d) tides arising out in the ocean
Explanation: The temperature difference between the water at the surface and water at depths up to 2 km is 20 K (20°C) or more. The warm surface-water is used to boil a volatile liquid like ammonia. The vapours of the liquid are then used to run the turbine of generator. The cold water from the depth of the ocean is pumped up and condenses vapour again to liquid.
Question 8. The major problem in harnessing nuclear energy is how to
(a) split nuclei
(b) sustain the reaction
(c) dispose of spent fuel safely
(d) convert nuclear energy into electrical energy
Explanation: The major hazard of nuclear power generation is the storage and disposal of spent or used fuels – the uranium still decaying into harmful subatomic particles (radiations). Improper nuclear-waste storage and disposal result in environmental contamination.
Question 9. Which part of the solar cooker is responsible for greenhouse effect?
(a) Coating with black colour inside the box
(c) Glass sheet
(d) Outer cover of the solar cooker
Explanation: Solar cookers are covered with a glass plate which traps infrared radiations (heat) from sunlight and does not allow them to escape. In other words we can say that it provides greenhouse effect.
A black surface absorbs more heat as compared to a white or a reflecting surface under identical conditions.
Solar cookers achieve a higher temperature by using mirrors to focus the rays of the Sun.
Question 10. The main constituent of biogas is
(b) carbon dioxide
(d) hydrogen sulphide
Explanation: Bio-gas is an excellent fuel as it contains up to 75% methane. It burns without smoke, leaves no residue like ash in wood, charcoal and coal burning. Its heating capacity is high. Bio-gas is also used for lighting.
Question 11. 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
(d) can be increased by planting tall trees close to the tower
Explanation: Power generated in a windmill depends on the velocity with which wind is moving.
Question 12. 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
(d) Waste from a nuclear power plant can be easily disposed off
Explanation: The Sun has been radiating an enormous amount of energy at the present rate for nearly 5 billion years and will continue radiating at that rate for about 5 billion years more. So, it can be taken as an inexhaustible source of energy.
Fossil fuels inside the earth are present in very limited amount.
Hydro and wind energy plants run with the help of air and do not cause any pollution.
It is very difficult to dispose waste from a nuclear power plant.
Question 13. 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
(d) more water molecules dissociate into ions
Explanation: Water at greater height has more potential energy. When it falls it will have greater kinetic energy associated with it. A larger amount of potential energy is converted into kinetic energy due to which more electric power will be obtained.
Question 14. 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 utilizing the energy of rotational motion of the blades of a windmill is to run the turbine of an electric generator
Answer. (a), (b)
Explanation: Maximum wind power is harnessed in open space hence, option (a) is wrong.
Moving air have kinetic energy which on hitting at the blades of a windmill causes them to rotate.
To generate wind power, we require wind at a very high speed. Due to this motion it possess kinetic energy and as such they are capable of doing mechanical work by virtue of its motion.
The energy possessed by the wind is due to its high speed. When the blowing wind strikes across the blades of a windmill, it exerts a force on them due to which the blades of the windmill start rotating. This rotational motion of the blades is used to run the turbine of an electric generator. Thus, the option (b) is the incorrect statement.
Question 15. Choose the incorrect statement.
(a) We are encouraged to plant more trees so as to ensure clean environment and also provide biomass fuel
(b) Gobar-gas is produced when crops, vegetable wastes etc., decompose in the absence of oxygen
(c) The main ingredient of biogas is ethane and it gives a lot of smoke and also produces a lot of residual ash
(d) Bio-mass is a renewable source of energy
Explanation: The main ingredient of biogas is methane. Except option (c), all other options are correct.