JAC Class 10 Science Solutions Chapter 14 Sources of Energy

Jharkhand Board JAC Class 10 Science Solutions Chapter 14 Sources of Energy Textbook Exercise Questions and Answers.

JAC Board Class 10 Science Solutions Chapter 14 Sources of Energy

Jharkhand Board Class 10 Science Sources of Energy Textbook Questions and Answers

Question 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 cloudy day

Question 2.
Which of the following is not an example of a biomass energy source?
A. wood
B. gobar-gas
C. nuclear energy
D. coal
Answer:
nuclear energy

Question 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. biomass
Answer:
nuclear energy

Question 4.
Compare and contrast fossil fuels and the sun as direct source of energy.
Answer:

Fossil Fuel	Sun
It is non-renewable and exhaustible source of energy.	It is renewable and non-exhaustible source of energy.
It causes environmental pollution.	It is non-polluting source.
Fossil fuels have to be extracted for use.	It is easily available for most of the time and at most the places throughout the year in our country.
Sun is indirect source of energy in fossil fuel.	Nuclear fusion reactions are the source of energy in the sun.
It is conventional source of energy.	It is non-conventional source of energy.

Question 5.
Compare and contrast biomass and hydroelectricity as source of energy.
Answer:

Biomass	Hydroelectricity
It causes pollution.	It is pollution free source of energy.
It is less expensive.	It is expensive in terms of construction of dams.
It is in the form of wood, cow-dung cake, agricultural residue etc.	Potential energy of water is used to generate electricity.
A fuel gas (biogas) can be produced by using it.	No gas is produced by using it.

Question 6.
What are the limitations of extracting energy from (a) the wind? (b) waves? (c) tides?
Answer:

Energy Source	Limitations of extracting energy
(a) The wind	The required wind speed should be higher than 15 km/h, the initial cost of establishment of wind farm is high, large area is required, high level of maintenence for wind farm is needed.
(b) Waves	It is costly and difficult to manage, the waves are generated by strong winds blowing across the sea.
(c) Tides	There are limited locations where dams for to harness tidal energy can be built. Efficient commercial exploitation is difficult.

Question 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:

• Exhaustible : Fossil fuel, coal will get depleted some day.
• Inexhaustible : Wind, tidal, solar energy, etc. are in the form continuing or repetitive currents of energy.
• Renewable : Biomass, if we manage properly, it can give a constant supply of energy at a particular rate.
• Non-renewable : Fossil fuels as once used up, they are lost forever and cannot be renewed.
  Yes, options given in ( a) and (b ) are same.

Question 8.
What are the qualities of an ideal source of energy?
Answer:
A good source of energy has following properties :

• It would able to do a large amount of work per unit volume or mass.
• It can be easily accessible.
• It can be easy to store and transport.
• It can be economical.

It should be pollution free and should not leave any residue.

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

Advantages	Disadvantages
It does not cause any pollution.	It cannot be used at night and on cloudy days.
It uses renewable/ inexhaustible source of energy.	It takes comparati-vely more time for cooking
Food nutrients are maintained during cooking, because the food is cooked at a comparatively low temperature.	The position of miror which reflects sunrays need to be monitored and the direction has to be changed again and again.
	It cannot be used for frying and to cook chapattis.

Yes, the place where Sun shine/solar energy is insufficient, the utility of solar cooker would be limited. Also on a rainy and cloudy day solar cooker cannot work.

Question 10.
What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Answer:
The energy demand is increasing day by day. Exploiting any source of energy may adversely affect the environment more or less.

For example, use of fossil fuels cause air pollution. It may lead to greenhouse effect, acid rain, etc. Use of Hydropower to generate electricity destroys large ecosystem.

Following steps are suggested to reduce energy consumption :

• Minimise the regular use of personal vehicles and use of public transport as far as possible.
• Maximise the use of pollution free source of energy.
• Use of eco-friendly fuels such as biogas, CNG, etc.
• Switch off the light, fan and other electric appliances, whenever not in use.
• Turn off the vehicles at traffic signal while waiting for green signal.
• Use of solar cooker, solar water heater.

Jharkhand Board Class 10 Science Sources of Energy InText Questions and Answers

Question 1.
What is a good source of energy?
Answer:
A good source of energy has following properties :

• It would able to do a large amount of work per unit volume or mass.
• It can be easily accessible.
• It can be easy to store and transport.
• It can be economical.

Question 2.
What is a good fuel?
Answer:
A good fuel is the one.

• Which burns completely without producing smoke or ash.
• Which produces large amount of heat while burning a small quantity of it.
• Which is easily available and economical.

Question 3.
If you could use any source of energy for heating your food, which one would you use and why?
Answer:
If we live in a village, gobar gas will be used as a fuel for heating our food because it has high calorific value and it is easily available and more economic.

If we live in a city, either LPG or microwave or oven can be used as fuel for heating our food, because LPG is pollution free. Microwave or oven is more preferable because nutritive value of food is maintained during heating our food.

Question 4.
What are the disadvantages of fossil fuels?
Answer:
The disadvantages of fossil fuels are :

• It is non-renewable source of energy.
• Air pollution is caused by burning of fossil fuels. Acidic oxides of nitrogen and sulphur are released on burning of fossil fuels which lead to acid rain.
• Gases like carbon dioxide causes green house effect and global warming.

Question 5.
Why are we looking at alternative sources of energy?
Answer:
We are looking at alternative sources of energy because the growing demand for energy was largely met by the fossil fuels. Our technologies were also developed for using fossil fuels i.e., coal and petroleum. The fossil fuels are non-renewable source of energy.

These fuels were formed over millions of years ago and there are only limited reserves. If we are to continue consuming these sources at such alarming rate, we would soon run out energy. To overcome this, alternative sources of energy are explored.

Question 6.
How has the traditional use of wind and water energy been modified for our convenience?
Answer:
The traditional use of wind energy has been modified by constructing wind fans and wind energy farm to generate electricity. The traditional use of water energy has been modified by constructing dams and convert the potential energy of falling water into electricity for our convenience.

Question 7.
What kind of mirror – concave, convex or plain – would be best suited for use in a solar cooker? Why?
Answer:
Use of concave mirror is best suited for solar cooker because it is a converging mirror that converges large amount of sun rays into the solar cooker.

Question 8.
What are the limitations of the energy that can be obtained from the oceans?
Answer:
The limitations of energy obtained from oceans are as follows :

• The locations, where dams can be built for tidal energy are limited.
• The wave energy is obtained only where strong winds are blowing accross the sea.
• Efficient commercial exploitation of ocean thermal energy is difficult.

Question 9.
What is geothermal energy?
Answer:
The heat energy which can be exploited from the steam trapped in rocks near the hot springs is called geothermal energy.

Question 10.
What are the advantages of nuclear energy?
Answer:
The advantages of nuclear energy are :

• It produces much more energy than the other conventional sources. For example, the fission of an atom of uranium produces 10 million times the energy produced by the combustion of an atom of carbon from coal.
• As compared to the space required to harness hydro energy, thermal energy, etc. less space is required to harness nuclear energy.

Question 11.
Can any source of energy be pollution free? Why or why not?
Answer:
Solar energy, wind energy, geothermal energy, etc. are considered as pollution free. But every time a source of energy is exploited or used, it causes envirnomental pollution. So, no source of energy can be pollution free.

Question 12.
Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?
Answer:
Yes, hydrogen is a cleaner fuel than CNG because hydrogen burnt in presence of oxygen produces water vapours (H₂O_(g)) whereas CNG that contain methane burns to produce carbon dioxide and carbon monoxide.

Question 13.
Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Answer:

• Hydropower, since the water in the reservoir would be refilled each time it rains.
• Wind power, as wind keeps blowing due to unequal heating of the landmass and water bodies by solar radiation.

Question 14.
Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
Answer:
Fossil fuels, i.e., coal and petroleum are exhaustible because once they are used up they are lost forever.

Activity 14.1 [T. B. Pg. 242]

Questions:

Question 1.
List four forms of energy that you use from morning, when you wake up, till you reach the school.
Answer:

• Muscular energy – To brush, exercise, take bath, to ride bicycle
• Electrical energy – To turn on geyser, to iron uniform, to put on the fan
• Fuel energy/PNG – To boil milk, cooking food; Transport – Going to school by bus / car
• Chemical energy / food – Breakfast, lunch

Question 2.
From where do we get these different forms of energy?
Answer:

Form of energy	Sources
Muscular energy	Energy stored in muscle cells in form of ATP
Electrical energy	From power plant
Fuel energy	From gas station
Chemical energy	From food

Question 3.
Can we call these sources of energy? Why or why not?
Answer:
Yes, we can call all these as sources of energy.

Activity 14.2 [T. B. Pg. 243]

Consider the various options we have when we choose a fuel for cooking our food.

Questions :

Question 1.
What are the criteria you would consider when trying to categorise something as a good fuel?
Answer:
The criteria to categorise good fuel for cooking our food are as follows :

• It should be easily available.
• It should be economical.
• It should not produce smoke or ash.
• It should have high efficiency.

Question 2.
Would your choice be different if you lived …
(a) in a forest?
(b) in a remote mountain village or small island?
(c) in New Delhi?
(d) lived five centuries ago?
Answer:

We live in	Our choice will be
(a) in a forest	wood, dry leaves
(b) in a remote mountain village or small island	wood, dry leaves, cow-dung cake
(c) in New Delhi	LPG, PNG
(d) lived five centuries ago	wood

Question 3.
How are the factors different in each case?
Answer:
In each case, the factors are different on the basis of its availability.

Activity 14.3 [T. B. Pg. 244]

To demonstrate the process of thermoelectric production with a model.

Apparatus and materials: Pressure cooker, pipe, tennis ball, metal sheet, dynamo, bulb.

Procedure:

• Take a table-tennis ball and make three slits into it.
• Put semicirucular fins cut out of a metal sheet into these slits.
• Pivot the tennis ball on an axle through its centre with a straight metal wire fixed to a rigid support.
• Ensure that the tennis ball rotates freely about the axle.
• Now connect a cycle dynamo to this.
• Connect a bulb in series.
• Direct a jet of water or steam produced in a pressure cooker at the fins.
• Note down your observation.
  

Observation : The bulb gets lighted.

Questions :

Question 1.
Which energy conversion do you think is taking place in this model?
Answer:
Heat energy gets converted to electrical energy in this model.

Question 2.
Which structure in the model acts as a turbine?
Answer:
Tennis ball fitted with metal sheets in the model acts as a turbine.

Question 3.
How electricity generated in this simple model?
Answer:
The heat given to pressure cooker produces steam. The steam is used to turn the tennis ball (the turbine). The tennis ball is further linked to a dynamo. Therefore, armature of a dynamo rotates and generates electricity.

Question 4.
What do the simplest turbines have?
Answer:
The simplest turbines have one moving part, a rotor assembly.

Question 5.
Which form of energy is essential in today’s life?
Answer:
Electrical energy is essential in today’s life.

Question 6.
What is your conclusion from this activity?
Answer:
Energy can be converted from one form to another.

Activity 14.4 [T. B. Pg. 248]

Find out from your grandparents or other elders

Questions :
(a) how did they go to school?
(b) how did they get water for their daily needs when they were young?
(c) what means of entertainment did they use?
Compare the above answers with how you do these tasks now.
Is there a difference? If yes, in which case more energy from external sources is consumed?
Answer:

Our grand parents	We are
(a) They went to school by walking.	(a) We use activa, a car or a school bus.
(b) They got water from wells, river, etc.	(b) We get water from bore by using submercible water pump.
(c) Social gathering, group meeting, drama, fairs, festival celebration, etc. were the means of their entertainment.	(c) We are using mobile phones, computers most of times. Besides it television, watching

Yes, today we consume much more energy. This is used for transport and day-to-day living.

Activity 14.5 [T. B. Pg. 249]

To demonstrate, “black surface absorbs more heat as compared to a white surface”.

Apparatus – Materials :
Conical flasks, water, thermometer

Procedure :

• Take two conical flasks and paint one white and the other black.
• Fill water in the both flask.
• Place the conical flasks in direct sunlight for half an hour to one hour.
• Measure the temperature of the water in both conical flask with a thermometer.

Questions :

Question 1.
If you touch the conical flasks, which one is hotter?
Answer:
Conical flask painted black is hotter.

Question 2.
Which property is used in solar cooker and solar water heater?
Answer:
A black surface absorbs more heat as compared to a white or a reflecting surface under identical conditions.

Question 3.
In which ways this finding can be used in our daily life?
Answer:
Wearing black coloured clothes in winter and white colour clothes in summer. White paint on the outer wall as well as white coating on terrace helps to maintain 2 – 3 °C low temperature inside the house during summer.

Activity 14.6 [T. B. Pg. 249]

To study the structure and working of a solar cooker and/or water heater.

Activity is done for understanding how the solar equipments are insulated and how does maximum heat absorption is ensured.

Property: A black surface absorbs more heat.

Structure :

• It consists of an insulated metal box or a wooden box which is painted black from inside.
• The box has a thick glass sheet as a cover over the box.
• A plane or concave mirror is attached to the box that acts as a reflector.
• Mirror focuses the rays of the sun into the box.

Questions :

Question 1.
Why is a glass sheet used?
Answer:
A glass sheet is used to creates greenhouse effect.

Question 2.
How is heat reflected into the box?
Answer:
By using mirror, rays of sun reflect the heat into the box.

Question 3.
State energy conversion in solar cooker/solar water heater.
Answer:
Light energy / solar energy in converted to heat energy.

Question 4.
What temperature is achieved in solar cooker / solar water heater?
Answer:
Typically solar cooker is designed to achieve 65 °C (150 °F) temperature. The temperature of water in the solar water heater is determined by the combination of collector area and the tank capacity. Typically it would be 50-60°C, which is much hotter than the bathing water temperature (around 40 °C).

Question 5.
State the advantages and limitations of using the solar cooker or solar water heater.
Answer:

Advantages	Limitations
1. Use of solar energy, which is available free of cost,	1. These devices are useful only at certain times during the day.
2. We can save fuel gas by using it.	2. These devices are not useful in cloudy days and at night.

Activity 14.7 [T. B. Pg. 252]

Discuss in the class following questions:

Question 1.
What is the ultimate source of energy for biomass, wind and ocean thermal energy?
Answer:
Sun / Solar energy is the ultimate source of energy for biomass, wind and ocean thermal energy.

Question 2.
Is geothermal energy and nuclear energy different in this respect? Why?
Answer:
Yes, geothermal energy is obtained from steam generated in regions of hot spots due to geological changes.
Nuclear energy is obtained by a process called nuclear fission and nuclear fusion of radioactive substances.

Question 3.
Where would you place hydroelectricity and wave energy?
Answer:
Hydroelectricity and wave electricity can be placed under renewable energy sources.

Activity 14.8 [T. B. Pg. 253]

To collect the information about various energy sources and how each one affects the environment.

Debate the merits and demerits of each source and select the best source of energy on this basis.

Sources of energy	Adverse effects on environment
1. Fossil fuel	Air pollution, acid rain, greenhouse effect
2. Thermal power	Air pollution, water pollution
3. Hydropower	Large eco-systems destroy agricultural land get submerged.
4. Biomass	Smoke, ash, and gaseous substances pollute air
5. Wind power	No adverse efffect
6. Solar energy	No adverse efffect
7. Tidal / Wave / Ocean thermal energy	No adverse efffect
8. Geothermal energy	No adverse efffect
9. Nuclear energy	Radioactive pollution, radiation

Based on this, solar energy is best energy soure. wind, ocean energy sources ultimately derive their energy from the sun. Solar energy is inexhaustible.

Activity 14.9 [T. B. Pg. 254]

Debate the following two issues in class: 9uestions:
(a) The estimated coal reserves are said to be enough to last us for another two hundred years. Do you think we need to worry about coal getting depleted in this case? Why or why not?
Answer:
Coal is used in large amount in thermal power stations for to generate electricity. The use of coal generates pollutants as the coal burns. Coal is also non-renewable resource, once depleted, it cannot be restored back. It will last only for 200 years, but formation of coal has taken millions of years and therefore we should use it with great care.

(b It is estimated that the sun will last for another five billion years. Do we have to worry about solar energy getting exhausted? Why or why not?
Answer:
We have not to worry about solar energy getting exhausted because the sun will last for another five billions years. We will have
to develop advanced technology for to trap and store more and more solar energy.

(c) On the basis of the debate, decide which energy sources can be considered –

• Exhaustible
• Inexhaustible
• Renewable
• on-renewable.

Give your reasons for each choice.
Answer:

• Exhaustible : Fossil fuel, coal will get depleted some day.
• Inexhaustible : Wind, tidal, solar energy, etc. are in the form continuing or repetitive currents of energy.
• Renewable : Biomass, if we manage properly, it can give a constant supply of energy at a particular rate.
• Non-renewable : Fossil fuels as once used up, they are lost forever and cannot be renewed.