NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy

CBSE NCERT solutions for ch 14 science class 10 sources of energy topic 14.1 What is a good source of energy?

Q. 1. What is a good source of energy?

Answer:

A good source of energy has the following properties.

(i) It is easily available.

(ii) It is economical.

(iii) Has a high calorific value.

(iv) It's use must not cause pollution.

(v) Must be safe to store and easy to transport.

Q. 2. What is a good fuel?

Answer:

A good fuel has the following properties.

(i) It is easily available.

(ii) It is economical.

(iii) Has a high calorific value.

(iv) It's combustion must not produce any poisonous smoke.

(v) Must be safe to store and easy to transport.

(vi) Has an ignition temperature well above the room temperature.

(vii) Ash or residue must not be produced on combustion.

(viii) The combustion must be easily controllable.

Q. 3. If you could use any source of energy for heating your food, which one would you use and why?

Answer:

I would use Solar energy as it is available free of cost and does not cause any pollution.

Solutions of NCERT for class 10 science chapter 14 sources of energy topic 14.2 Conventional sources of energy:

Q. 1. What are the disadvantages of fossil fuels?

Answer:

The disadvantages of fossil fuels are the following:

(i) Their combustion produces smoke causing air pollution.

(ii) They produce carbon dioxide on burning which causes green house effect and is therefore responsible for global warming.

(iii) They produce oxides of Sulfur and Nitrogen on burning which cause acid rain.

(iv) Fossils fuels are not a renewable source of energy.

Q. 2. Why are we looking at alternate sources of energy?

Answer:

We are looking at alternate sources of energy primarily because of the following two reasons.

(i) Traditionally used fossil fuels are exhaustible and non-renewable and therefore eventually we would run out of them.

(ii) The burning of fossil fuels causes pollution of the atmosphere, soil and our water bodies and cause global warming which has posed a serious threat to the environment.

Q. 3. How has the traditional use of wind and water energy been modified for our convenience?

Answer:

Wind energy is utilised through the construction of wind mill farms.

Water energy is utilised by building hydro-power plants. The kinetic energy of the water is used to produce electricity by rotating the arms of a generator.

NCERT solutions for class 10 science chapter 14 sources of energy topic 14.3 Alternative or non conventional sources of energy:

Q. 1. What kind of mirror - concave, convex or plain - would be best suited for use in a solar cooker? Why?

Answer :

Concave mirror would be best suited in a solar cooker as it will be able to produce a concentrated beam of high intensity which will produce more heat.

Q. 2. What are the limitations of the energy that can be obtained from the oceans?

Answer:

The forms of energy that can be obtained from the ocean are mainly tidal energy, wave energy and thermal energy. The limitations in harnessing these forms of energy are the following

(i) There are very few sites in the world where high tides are regularly present.

(ii) There are very few shores where waves of high kinetic energy reach regularly.

(iii) To harness the ocean's thermal energy the Temperature difference between the surface and the depth must be at least 20 ^o C. Again such sites are very less.

Q. 3. What is geothermal energy?

Answer:

Energy stored inside the earth in form of thermal energy is called geothermal energy. Due to geological changes the lava present in the core of the earth is pushed towards the surface of the earth thus creating places having extremely high temperature called hot spots.

When water comes in contact with these hot spots high pressure steam is formed which can be used to generate electricity.

Q. 4. What are the advantages of nuclear energy?

Answer:

Nuclear energy has the following advantages:

(i) It's calorific value is much larger than conventional fossil fuels.

(ii) By regulating rate of nuclear fission energy can be generated at very high rate.

(iii) Nuclear fission does not form any smoke.

(iv) Once fully loaded a nuclear reactor can produce high amounts of energy for very long time at a stretch without having to be reloaded.

CBSE NCERT Chapter 14 science class 10 sources of energy topic 14.4 Environmental consequences:

Q. 1. Can any source of energy be pollution-free? Why or why not?

Answer:

No source of energy can be completely pollution free.

Even if the production of energy through a source does not harm the environment the formation of the assembly required to harness the energy would cause some minimal amount of pollution e.g. Solar energy, Hydro energy.

Q. 2. Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?

Answer:

Of course Hydrogen is a cleaner fuel than CNG because burning hydrogen produces only water which is not harmful for the environment at all whereas combustion of CNG produces carbon dioxide causing green house effect and other harmful oxides causing acid rain.

NCERT solutions for class 10 science chapter 14 sources of energy topic 14.5 How long will an energy source last us?

Q. 1. Name two energy sources that you would consider to be renewable. Give reasons for your choices.

Answer:

The following sources of energy are renewable:

(i) Wind energy is renewable as winds will be moving as long as the normal behavior of the weather and our environment persists.

(ii) Hydro energy is renewable as hydro energy can be harnessed as long as the flowing water bodies like rivers and waterfalls exist.

Q. 2. Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.

Answer:

The following resources of energy are exhaustible:

(i) Fossil fuels are exhaustible as they take millions of years to form which is practically forever as compared to the rate at which they are being exhausted.

(ii) Nuclear sources are exhaustible as the number of nuclear fuels on the earth is limited.

Solutions of NCERT for class 10 science 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.

Answer:

A solar water heater cannot be used to get hot water on a cloudy day as much sun light won't be present for energy to be harnessed.

(b) is the correct answer.

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

Answer:

Nuclear energy is not an example of a bio-mass energy source as its origin is not biological elements.

(c) is the correct answer.

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

Answer:

Geothermal energy is not ultimately derived from the Sun’s energy, it's origin is the high-temperature molten rocks present in the core of the earth.

(a) is the correct answer.

Q. 4. Compare and contrast fossil fuels and the Sun as direct sources of energy.

Answer:

Both fossil fuels and solar energy are direct sources of energy but have the following differences between them.

Q. 5. Compare and contrast bio-mass and hydro electricity as sources of energy.

Answer:

Q. 6(a). What are the limitations of extracting energy from (a) the wind?

Answer:

Wind mill farms can be set only at places where fast flowing winds are present throughout the year and such sites are very less.

Also the setting up of wind mill farms is a very expensive process and requires large areas of land.

Q. 6(b). What are the limitations of extracting energy from (b) waves?

Answer:

Energy from waves can be efficiently harnessed at very few sites as there are very less places where high energy waves are present throughout theyear.

Q. 6(c). What are the limitations of extracting energy from (c) tides?

Answer:

Energy from tides can be efficiently harnessed at very few sites as there are very less places where high energy tides are present throughout the year.Setting up of the tidal dams is also an expensive process and the energy harnessed is also not very large.

Q. 7. On what basis would you classify energy sources as

(a) renewable and non-renewable?

(b) exhaustible and inexhaustible?

Are the options given in (a) and (b) the same?

Answer:

(a) The sources of energy that are replenished by the nature are called renewable sources and those which are not replenished by the nature are called non-renewable sources of energy.

(b) The sources of energy that are present in a limited quantity and would get over after some time are callued exhaustible sources of energy and those which are available in infinite amount by the virtue of nature are called inexhaustible sources of energy.

The options given in (a) and (b) are the same.

Q. 8. What are the qualities of an ideal source of energy?

Answer:

An ideal source of energy should have the following properties:

(i) Must be providing sufficient quantities of energy.

(ii) Must be economical to harness.

(iii) Must not cause pollution of the environment.

(iv) Must be easy, cheap and safe to store and transport.

Q. 9. What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?

Answer:

Advantages of the solar cooker are the following:

(i) Use of solar cooker saves precious and exhaustible sources of energy such as LPG.

(ii) Use of solar cooker is environment-friendly as opposed to combustible sources of energy.

(iii) Solar energy is available free of cost to all.

Disadvantages of the solar cooker are the following.

(i) A solar cooker can be used only during day time.

(ii) A solar cooker cannot be used on a cloudy day.

Q. 10. What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?

Answer:

Some of the environmental consequences of the ever-increasing demand for energy are the following:

(i) Combustion of fossil fuels is causing air pollution, acid rain and global warming.

(ii) Buiding of hydropower plants disturbs the ecological balance of the water bodies and aquatic organisms.

(iii) The ever increasing demand of firewood has severely decreased the forest area causing global warming.

(iv) Use of nuclear sources poses the risk of radioactivity caused by nuclear waste.

Some of the steps that could be taken to reduce energy consumption are.

(i) Switching off the lights, fans, air-conditioners etc. when not in use.

(ii) Using efficient electrical appliances.

(iii) Using a bicycle or public mode of transport to reduce the consumption of fossil fuels.