The fourteenth chapter in the NCERT Book for Class 10 Science focuses on the different Sources of Energy, along with their advantages and disadvantages. The chapter talks about Conventional Sources of Energy (Fossil Fuels, Thermal Power Plants, and Hydro Power Plants) and discusses the recent advancements in the technology for using conventional sources of energy (Bio-Mass and Wind Energy). You also learn about non-Conventional Sources of Energy (Solar Energy, Energy from the Sea, Geothermal Energy, and Nuclear Energy). Additional Information is provided on the Environmental Consequences of exploiting energy sources.
The topics in Chapter 14 include:
Through Home Revise, you can get all the topics from this chapter cleared quickly.
Chapter 14 - Sources of Energy Exercise
Q.1 A solar water heater cannot be used to get hot water on
(a) a sunny day.
(b) a cloudy day.
(c) a hot day.
(d) a windy day.
Ans: (b) a cloudy day.
Q.2 Which of the following is not an example of a bio-mass energy source?
(a) wood
(b) gobar-gas
(c) nuclear energy
(d) coal
Ans: (c) nuclear energy
Q.3 Most of the sources of energy we use represent stored solar energy. Which of the following is not ultimately derived from the Sun’s energy?
(a) geothermal energy
(b) wind energy
(c) nuclear energy
(d) bio-mass.
Ans: (a) geothermal energy
Q.4 Compare and contrast fossil fuels and the Sun as direct sources of energy.
Ans:
Fossil fuels:
1. It is conventional source of energy
2. The fossil fuels are non-renewable sources of energy.
3. The fossil fuels have limited reserves and are depleting very fast due to over use
4. Fossil fuels can be used for our energy requirement anytime
5. Use of Fossil fuels results in air pollution. The oxides of carbon, nitrogen and sulphur that are released on burning fossil fuels are acidic oxides. These lead to acid rain which affects our water and soil resources
6. Fossil fuels cost is initially low for short usage, but overall cost becomes high over a longer period
7. Fossil fuels involves recurring expenses.
Sun:
1. It is non-conventional source of energy
2. Sun is a renewable source of energy
3. Sun is a very large and long lasting source of energy
4.The energy from the Sun can be derived during day time only.
5. Solar energy is totally clean and Eco-friendly fuel. It can be produce without any pollution or ecological bad effects
6. The solar energy, initially cost high for small and limited usage but for longer period and large energy requirement its cost is minimum
7. Solar energy requires no recurring expenses
Q.5 Compare and contrast bio-mass and hydroelectricity as sources of energy.
Ans:
Biomass:
1. Biomass is a renewable and conventional source of energy.
2. Biomass as source of energy makes use of chemical reaction, hence exhibits a form of chemical energy
3. Application of biomass for energy requirement causes air pollution
4. Use of biomass does not cause ecological imbalance.
5. Biomass is relatively more economic source of energy than hydroelectricity.
Hydroelectricity:
1. Hydroelectricity is also a renewable and conventional source of energy.
2. Hydroelectricity makes use of kinetic energy of running or falling water from height
3. Hydro electricity is pollution free source of energy
4. Construction of hydle projects for hydroelectricity causes ecological imbalances.
5. Hydro Electricity is relatively costly source of energy.
Q.6 What are the limitations of extracting energy from—
(a) the wind?
(b) waves?
(c) tides?
Ans:
(a) Limitations of extracting energy from the wind -
i. Wind energy farms can be established only at those places where wind blows for the greater part of a year
ii. The wind speed should also be higher than 15 km/h to maintain the required speed of the turbine
iii. There should be some back-up facilities (like storage cells) to take care of the energy needs during a period when there is no wind
iv. Establishment of wind energy farms requires large area of land. For a 1 MW generator, the farm needs about 2 hectares of land
v. The initial cost of establishment of the farm is quite high
vi. the tower and blades are exposed to the vagaries of nature like rain, Sun, storm and cyclone, they need a high level of maintenance
(b) Limitations of extracting energy from the waves -
i. Wave energy is a viable proposition only where waves are very strong
ii. Nature , pattern and occurrence of waves is not same for different sea shore locations over time.
iii. Cost of energy production is high as a wide variety of devices are required to trap wave energy for rotation of turbine and production of electricity
(c) Limitations of extracting energy from the tides -
i. Tidal energy is harnessed by constructing a dam across a narrow opening to the sea. A turbine fixed at the opening of the dam converts tidal energy to electricity. The locations where such dams can be built are limited
ii. Cost of energy production is high as dam construction involves large capital cost
Q.7 On what basis would you classify energy sources as
(a) renewable and non-renewable?
(b) exhaustible and inexhaustible?
Ans:
(a) Renewable and non-renewable :
Renewable energy sources are those energy sources, which can be restored back to their original form after harnessing energy for various purpose, e.g. Hydro Electricity. Non-renewable energy sources are those energy sources, which can not be restored back to their original form or simply replenished after making use of them for energy requirement, e.g. Coal, Gas, Petrol etc.
(b) Exhaustible and inexhaustible :
Sources of energy, that will exhaust in near future, are called exhaustible source e.g. Gas, Petrol, Coal etc. Sources of energy, that will not end considerably over very long period of time are called inexhaustible sources, e.g. Sun, Water, Air etc.
Q.8 What are the qualities of an ideal source of energy?
Ans: The qualities of an ideal source of energy are:
i. An ideal source of energy is less polluting and while in use have minimum contribution towards ecological imbalance such as 'the green-house effect'
ii. It is cost effective and economical to use
iii. Its procurement, processing, storage and distribution is easy and manageable
iv. It would do a large amount of work per unit volume or mass
v. It can be employed for diverse energy need across different fields
Q.9 What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?
Ans:
Advantages of using a solar cooker:
i. It is totally pollution free
ii. It is cost effective and economical to use as there is no recurring cost.
iii. It is quite user friendly and easy to handle.
iv. It provides safety against fire related accident and injuries
v. It provides an ideal cooking environment with no loss food value
Disadvantages of using a solar cooker :
i. It takes considerably long time for food cooking
ii. Solar cookers cannot be used indoor, in night time or in cloudy weather
iii. During food processing, direction of solar cooker is required to be aligned with changing direction of the Sun
iv. It cannot be used for all purpose cooking e.g. making chapaties , roasting , frying
v. The availability and Intensity of Solar energy is not same for all the time at all the places.
Q.10 What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Ans: The unprecedented and ever increasing scale of urban development together with rapid pace of industrialization has fueled the demand for energy many folds. This ever increasing demand of energy has resulted in adverse environmental consequences, which are as given below:
i. To keep the pace of modern development, ever increasing demand for energy has resulted in indiscriminate usage and exploitation of energy resources, which is causing a great damage to environment and creating ecological-imbalances in the form of man made disasters such as greenhouse effect or global warming
ii. The available reserves of energy resources are limited. To meet the increasing demand for energy, these reserves are being depleted very fast, which may lead to theirs scarcity or energy crisis in near future.
To reduce energy consumption, following steps can be suggested:
i. We should make best use of public transport system such as Rails, Buses and should try to avoid private transport whenever and where ever possible
ii. We should adopt new life style of living with minimum waste of energy in Cooking, Home lighting, Cooling or heating
iii. The use of alternative or non-conventional sources of energy such as Solar energy, wind energy, hydro energy, Tidal energy, wave energy and Ocean Thermal Energy should be optimised to supplement the demand for energy from non-renewable source of energy.
iv. We should impose a ceiling on per capita energy consumption through limited availability or price linked with energy consumptions to discourage its misuse
Q.11 What is a good source of energy?
Ans:
A good source of energy has the following properties:
1.Be economical
2. Easy storage and transportation
3. Easy availability
4. Work done per unit volume or mass should be large.
Q.12 What are the disadvantages of fossil fuels?
Ans: Following are the disadvantages of fossil fuels:
1. Fossil fuels like coal and petroleum results in air pollution as there is release of huge amount of pollutants.
2. Gases such as carbon dioxide is released when a fossil fuel is burnt, which causes global warming.
3. Soil fertility and potable water is affected by the oxides of carbon, nitrogen, sulphur, etc. that are released from fossil fuels.
Q.13 What kind of mirror – concave, convex or plain would be best suited for use in a solar cooker? Why?
Ans: For a solar cooker the heat source is sunlight for heating and cooking. The reason why a mirror is used is to reflect and focus the sunlight at one point. So a concave mirror can be used in a solar cooker, as it focuses all the sunlight at one point resulting in increase in temperature, thereby heating and cooking the food.
Q.14 How has the traditional use of wind and water energy been modified for our convenience?
Ans: In olden days, wind energy was trapped used windmills to do mechanical works like lifting or drawing water from a well. But these days, windmills are used to generate electricity. The kinetic energy of wind is trapped and converted into electricity with the help of rotatory motion of the blades, which turns the turbine of the electric generator to produce electricity.
Similarly, waterfalls were the source of potential energy in olden days. But these days as the number of waterfalls has reduced, water dams are constructed and are used as a source to trap the potential energy. Here, the water falls from a certain height on the turbine producing electricity.
Q.15 What are the limitations of the energy that can be obtained from the ocean?
Ans: The different forms of energy that can be obtained from the ocean are tidal energy, wave energy and ocean thermal energy. Following are the limitations of the energy obtained from ocean:
1. The relative positioning of the earth, the sun and the moon has an impact on the tidal energy.
2. For the conversion of tidal energy into electricity, high dams are required.
3. To obtain electricity from wave energy, very strong waves are required.
4. For trapping the ocean thermal energy, there should be a temperature difference of more than 20°C between hot surface water and the cold water at a depth.
Q.16 What is geothermal energy?
Ans: Geothermal energy can be defined as the energy that is obtained from the earth. The energy can be obtained from the hot spots that are formed when the molten rocks at the core of the earth are pushed to the earth’s crust. Hot springs are used for the production of electricity in the geothermal power plants.
Q.17 What are the advantages of nuclear energy?
Ans: Following are the advantages of nuclear energy:
Amount of energy produced per unit mass is large
As it does not produce any pollutants, it is clean
Fission of 1 atom of uranium produces 10 million times the energy that is obtained by burning 1 atom of carbon.
Q.18 Can any source of energy be pollution-free? Why or why not?
Ans: No source of energy can be completely pollution-free. But solar cells are considered to be pollution-free. But their manufacturing may cause environmental damage. In case of nuclear energy, the waste produced after fusion is zero. But the wastes that are produced during fission are hazardous. Hence, no source of energy is pollution-free.
Q.19 Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?
Ans: Hydrogen gas is cleaner than CNG as CNG contains hydrocarbons. Carbon is a form of pollutant in CNG. On the other hand, hydrogen is waste-free and the fusion of hydrogen does not produce any waste. Hence, hydrogen as a rocket fuel is cleaner than the CNG.
Q.20 Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Ans: Following are the two sources of energy that are renewable:
1. Wind: Wind energy is obtained from the air which is blowing at a high speed. Wind energy is trapped using windmills so as to generate electricity. Blowing of air is dependent on uneven heating of the earth. Since the heating of the earth is forever, wind availability will also be forever.
2. Sun: The energy obtained from the sun is known as solar energy. It is produced by the fusion of hydrogen into helium, fusion of helium into other heavy metals and it continues. A large amount of hydrogen and helium is available in the sun which will never be exhausted. Hence, solar energy is renewable source of energy.
Q.21 Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
Ans: Following are the two sources of energy that are exhaustible:
1. Wood: The source of wood are forests. Due to deforestation the number of forests are reducing. We know that it takes years to grow forest. If the rate of deforestation increases, the availability of wood will decrease. Hence, wood is an exhaustible source of energy.
2. Coal: The source of coal is from the dead remains of the plants and animals that remained buried for years. Industrialization has increased the demand for coal and it cannot be replenished. Hence, coal is also an exhaustible source of energy.