Sunday, August 12, 2012

CBSE Class 10 - Science - Ch14 - Sources of Energy

Sources of Energy 
(Q & A)

Q1: Fill in the blanks.
(a) Hydro power plants convert _________ energy of falling water into electricity.

(b) When wood is burnt in a limited supply of oxygen, ______ is left behind as residue.

(c) Gases like ______, _____, ______ and ______ are generated in a biogas plant.

(d) Biogas contains _____ % methane.

(e) To maintain the required speed of the turbine, wind speed should be higher than _____.

(f) To establish 1 MW generator, the wind energy farm needs about ___ hectares of land.

(g) Ocean Thermal Energy plants can operate if the temperature difference between the water at the surface and water at depths up to ______ km is _______ or more.

(h) ______ and _______ countries have number of power plants based on geothermal energy.

Answer:

 (a) potential
 (b) charcoal
 (c)  methane (CH4), CO2, Hydrogen (H2) and H2S
 (d) 75%
 (e) 15 km per hr
 (f) 2 hectares
 (g)  2km, 293 K (20°C)
 (h) New Zealand and United States of America

Q2(NCERT): 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: (b) a cloudy day.


Q3(NCERT): 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: (c)  nuclear energy

Q4(NCERT): 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: (c)  nuclear energy

Q5: Which power plant works on the basis of gravity of earth?
(a) Geothermal
(b) Wind farms
(c) Hydropower
(d) Nuclear power

Answer: (c) Hydropower

Q6: Which of the following is not a fossil fuel?
(a) Wood
(b) Coal
(c) Petroleum
(d) Natural Gas

Answer: (a) Wood

Q7:  The energy source which will eventually run out is known as _____ .
(a) renewable resource
(b) non-renewable resource
(c) endangered resource
(d) none of these

Answer: (a) renewable resource


Q8: Which country is the leader in harnessing wind energy?
(a) Denmark
(b) Germany
(c) India
(d) USA

Answer: (b) Germany

Q9: Which of the following is a renewable source of energy?
(a) Uranium
(b) Petroleum
(c) Coal
(d) Biomass

Answer: (d) Biomass


Q10: Which of the following element is used in making solar cells?
(a) Gold
(b) Carbon
(c) Silicon
(d) Silver

Answer: (c) Silicon. (Note: silver is used for interconnection of the solar cells in the panel).


Q11(NCERT): What is a good fuel? 
             or
What are the qualities of a good fuel?

Answer:






Q12(NCERT): What is a good source of energy?

Answer: Following attributes are considered for a good source of energy:

  1. Resource should provide adequate amount of energy. i.e. which would do a large amount of work per unit volume or mass
  2. Should be convenient to use and is accessible.
  3. Easy to transport and store.
  4. Should be able to fulfill demand of energy for a longer duration.
  5. Easily be converted to energy forms used in day to day operations.

Q13(CBSE): Which one of the following is a renewable resource?
(a) Natural gas,
(b) petroleum,
(c) ground water,
(d) coal.

Answer: (c) ground water

Q14: How do fossil fuels lead to acid rain?

Answer: Most of the fossil fuels like coal or petroleum products contain carbon and traces of nitrogen and sulphur. 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.

Q15: Which form of energy is harnessed by a turbine to convert it into an electrical energy?

Answer: Mechanical energy.


Q16: Which one of the following is main reason that Solar energy is not a main source of generating electrical power?

(a) It pollutes the environment.
(b) It is a non-renewable source.
(c) It is very expensive.
(d) It produces very less amount of energy.

Answer:  (c) It is very expensive.

Q17: The spots are sources of _______ energy.
(a) Wind
(b) Geothermal
(c) Nuclear
(d) Hydroelectric

Answer: (b) Geothermal


Q18: 1 atomic mass unit (u) is equivalent to how many electron volts?
(a) 1 Mev
(b) 931 MeV
(c) 1.602 MeV
(d) 10  MeV

Answer:  (b) 931 MeV

Q19: What are the disadvantages of Hydro power plant?

Answer: Disadvantages are:
  1.  Requires expensive infrastructure. 
  2. All river sites are not suitable for construction of dams.
  3. A large of human habitation and land gets submerged at the dam-site. People displaced loose their business and homes. Social problems arise.
  4. Environmental challenges exist. Flooding of  nearby areas gives constant threat to natural environment.
  5. It may increase the risk of earthquakes. 

Q20: Where in India projects are run to harness Tidal energy?

Answer: Gulf of Kutch, Gujarat and West Bengal.

Q21: What is pyrolysis?

Answer: It is a thermochemical process of decomposing organic matter at high temperature in the absence of oxygen. e.g. charcoal is obtained by this process.

Q22: How charcoal is obtained? Why is charcoal a better fuel when compared to wood?

Answer: Charcoal is obtained through pyrolysis process i.e. when wood is burnt in a limited supply of oxygen, water and volatile materials present in it get removed and charcoal is left behind as the
residue.
Charcoal burns without flames, is comparatively smokeless and has a higher heat generation efficiency.

Q23: What is bio-mass?

Answer: Biomass is any organic matter that is renewable over time. Biomass has been a steady source of fuel. e.g. wood, live stock, agriculture bio-mass are sources of renewable energy.
Examples of fuel obtained from bio-mass are:
  1. Charcoal is obtained  from wood.
  2. Bio-gas is obtained from animal waste (cow-dung etc.)
  3. Bio-diesel is obtained from sugar cane and oilseed crops.

Q24: Why are thermal power plants setup near coal and oil fields?

Answer: It minimizes the cost of transportation and therefore it reduces the cost of production also.
Transporting (Transmission) electricity over wires is lot cheaper than transporting raw material (oil and coal).

Q25(CBSE):Name the largest component of biogas. (1 mark)

Answer: Methane 75%

Q26: What is Solar Constant?

Answer: The solar energy fall on the earth’s atmosphere exposed perpendicularly to the rays of the Sun at the average distance between the Sun and earth is known as the solar constant. It is estimated to be 1.4 kW per square meter.

Q27: What are the advantages of Solar Panel?

Answer:
  1. Low cost maintenance
  2. Have no moving parts
  3. Can work efficiently without any aid of focussing device.
  4. Can be set up in remote and inaccessible hamlets or very sparsely inhabited areas.
  5. Provides pollution free, noiseless energy.

Q28: What are the advantages and disadvantages of Wind energy?

Answer: Advantages of Wind Energy are:

  • Renewable Source
  • Eco friendly
Disadvantages of Wind energy are:
  • Wind speed is not available all the time and its speed is not uniform.
  • Huge investment is required for setup.
  • Needs a large area to setup series of wind mills.
  • Output gains may be quite low when compared to investment cost.



(In progress ...)

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