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Renewable sources of energy - class-VIII

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In a wind mill the electric energy is converted into mechanical energy.         

  1. True

  2. False

  3. Ambiguous

  4. Data insufficient


Correct Option: B
Explanation:

Answer is B.
Windmills, like waterwheels, were among the original prime movers that replaced animal muscle as a source of power. They were used for centuries in various parts of the world, converting the energy of the wind into mechanical energy for grinding grain, pumping water, and draining lowland areas.
Kinetic energy of the wind is transformed into mechanical energy of the turning windmill. This can be used to turn a generator to generate electricity. The original energy to cause the wind to blow came from the sun. Uneven heating of the earth's surface causes wind.
Hence, the statement is false.

65% by volume is hydrogen gas in the biogas. 

  1. True

  2. False

  3. Ambiguous

  4. Data insufficient


Correct Option: B
Explanation:

Answer is B.

Biogas is characterized based on its chemical composition and the physical characteristics which result from it. It is primarily a mixture of methane (${ CH } _{ 4 }$) and inert carbonic gas (${ CO } _{ 2 }$). However the name 'biogas' gathers a large variety of gases resulting from specific treatment processes, starting from various organic waste - industries, animal or domestic origin waste, etc . 
Hence, the statement is false.

The gas obtained by the fermentation of biomass is :

  1. LPG

  2. CNG

  3. hydrogen

  4. biogas


Correct Option: D
Explanation:

Fuel-grade ethanol is one energy source that has great potential for being generated from biomass. The gas obtained by the fermentation of biomass is called biogas.

Fill  in the blank.

Renewable source of energy is ______ .

  1. coal

  2. fossil fuel

  3. natural gas

  4. Sun


Correct Option: D
Explanation:

Renewable energy is generally defined as energy that comes from resources which are naturally replenished on a human time scale such as sunlight, wind, rain, tides, waves and geothermal heat. Hence, Sun is naturally coming and can be used in the form of solar energy, to evaporate water which turns into rain and rains are useful in many uses. Ultimately, Sun is the renewable source of energy.

Select the renewable and non-renewable sources of energy from the following:
(a) Coal
(b) Wood
(c) Water
(d) Diesel
(e) Wind
(f) Oil

  1. Renewable-(b), (c) and (e) and Non-renewable-(a), (d) and (f)

  2. Renewable-(a), (d) and (f) and Non-renewable-(b), (c) and (e)

  3. Renewable-(a), (d) and (e) and Non-renewable-(b), (c) and (f)

  4. Renewable-(a), (c) and (e) and Non-renewable-(b), (d) and (f)


Correct Option: A
Explanation:

Renewable- (b), (c) and (e); Non-renewable- (a), (d) and (f).
Here once petrol,diesel, coal and oil are consumed, for example in our vehicle, it cannot come back and renew to some other thing where as in wood, wind and water once we use it for some purpose we can use it for some other thing again like if wood is used in making bed then again we can make it back to wood or some other thing. Hence, these are renewable sources.

The source of renewable energy is :

  1. Petroleum

  2. Coal

  3. Uranium

  4. Tree


Correct Option: D
Explanation:

Unlike fossil fuels, trees are eternal sources of energy for animals. They absorb sunlight directly from the environment and keep on producing food for others as long as they exist.

Select the renewable and non-renewable sources of energy from the following:
(a) Coal
(b) Wood
(c) Water
(d) Diesel
(e) Wind
(f) Oil

  1. Renewable-(a), (d) and (f) and Non-renewable-(b), (c) and (e)

  2. Renewable-(b),(c) and (e) and Non-renewable-(a), (d) and (f)

  3. Renewable-(a), (c) and (e) and Non-renewable-(b), (d) and (f)

  4. Renewable-(b), (d) and (e) and Non-renewable-(a), (c) and (f)


Correct Option: B
Explanation:

Renewable-(b), (c) and (e); Non-renewable-(a), (d) and (f).
Here once petrol, diesel, coal and oil are consumed, for example in our vehicle, it cannot come back and renew to some other thing whereas in wood, wind and water once we use it for some purpose we can use it for some other thing again like if wood is used in making bed then again we can make it back to wood or some other thing. Hence, these are renewable sources.

In a thermoelectric station the energy Which changes into electric energy is :

  1. chemical energy

  2. potential energy

  3. nuclear energy

  4. heat energy


Correct Option: D
Explanation:

Answer is D.

The heat produced by either steam or coal is converted in to electrical energy. Thus, in a thermal power station, heat energy is converted to electrical energy.

Gobar gas is a:

  1. solid fuel

  2. liquid fuel

  3. primary fuel

  4. secondary fuel


Correct Option: D
Explanation:

Biogas is a type of secondary energy because biomass (primary energy) is used to produce biogas by anaerobic digestion into more efficient and higher value fuel.Biogas is also called gobargas as made by waste remains of plants and animals.

Which of the following is released from biomass?

  1. Cow-dung

  2. Methane

  3. Oxygen

  4. Helium


Correct Option: B
Explanation:

Major gases released from biomass are methane ($CH _4$), carbon dioxide ($CO _2$), hydrogen ($H _2$) and hydrogen sulphide ($H _2S$).

Which of the following is an indirect form of solar energy?

  1. Tidal energy

  2. Energy from wastes

  3. Geothermal energy

  4. Electricity


Correct Option: A

The device that uses solar energy in the form of heat is

  1. Solar light

  2. Solar panel used in artificial satellites

  3. Solar cell

  4. Solar cooker


Correct Option: D
Explanation:

A solar cooker is a device which uses the energy of direct sunlight to heat or cook. A mirrored surface with high specular reflectivity is used to concentrate light from the sun on to a small cooking area. Depending on the geometry of the surface, sunlight can be concentrated by several orders of magnitude producing temperatures high enough to melt salt and smelt metal. 

Thus heat of solar energy is used in cooking with a solar cooker.

Identify one of the uses of solar heater in the following.

  1. Conversion of solar energy into electrical energy

  2. Providing energy for artificial satellites

  3. Desalination of marine water

  4. Using in automatic streelights


Correct Option: C
Explanation:

There are two primary means of achieving desalination using solar energy, through a phase change by thermal input, or in a single phase through mechanical separation. Phase change (or multi-phase) can be accomplished by either direct or indirect solar distillation. Single phase is done by the use of photovoltaic cells to produce electricity to drive pumps.

The value of solar constant is then

  1. $2 kcal m^{-2}minute^{-1}$

  2. $20 kcal m^{-2}minute^{-1}$

  3. $2KWm^{-2}$

  4. $200Wm^{-2}$


Correct Option: A
Explanation:

The value of solar constant is fixed and it is equal to $1.951Kcal\quad m^{-2}minute^{-1}$  which can be rounded off.

The energy generated at the core of the sun is carried to surface by photons in about a million year because

  1. sun is a huge body

  2. photons travel very fast

  3. photons bounce so many times through the dense materials

  4. photons travel with the speed of light


Correct Option: C

A Carnot's engine working between 300 k and 500 k has working output of $1000 J$ per cycle.How much heat energy is supplied to the engine from the source in each cycle?

  1. $1500 J$

  2. $1600 J$

  3. $2000 J$

  4. $1400 J$


Correct Option: C

Solar energy provides _________.

  1. Wind energy

  2. Light energy

  3. Heat energy

  4. All the above


Correct Option: D

Solar energy is mainly caused due to:

  1. fusion taking place in the sun

  2. fusion of protons during synthesis of heavier elements:

  3. gravitational contraction

  4. burning of hydrogen in the oxygen


Correct Option: A

Density of the core of sun which is $10$ times that of gold or lead is about

  1. $100g{cm}^{-1}$

  2. ${120}g{cm}^{-1}$

  3. $150g{cm}^{-1}$

  4. $200g{cm}^{-1}$


Correct Option: C

Which of the following source of energy is not considered as the transformation of solar energy?

  1. Energy of food

  2. Energy of petroleum

  3. Energy of coal

  4. Energy of fission


Correct Option: A

The installed capacity of wind energy in India is about:

  1. 8000 MW

  2. 4000 MW

  3. 6000 MW

  4. 1500 MW


Correct Option: A
Explanation:

Wind power generation capacity in India has significantly increased in the last few years . The installed capacity of wind energy in India is about 8000MV.

The superheated steam is raised in geothermal plants by the heat of :

  1. magma

  2. lava

  3. either (a) or (b)

  4. none of these


Correct Option: C
Explanation:

Answer is C.

The heat from the earth's core continuously flows outward. It transfers (conducts) to the surrounding layer of rock, the mantle. When temperatures and pressures become high enough, some mantle rock melts, becoming magma. Then, because it is lighter (less dense) than the surrounding rock, the magma rises, moving slowly up toward the earth's crust, carrying the heat from below.
Sometimes the hot magma reaches all the way to the surface, where we know it as lava. But most often the magma remains below earth's crust, heating nearby rock and water (rainwater that has seeped deep into the earth) - sometimes as hot as 700 degrees F. Some of this hot geothermal water travels back up through faults and cracks and reaches the earth's surface as hot springs or geysers, but most of it stays deep underground, trapped in cracks and porous rock. This natural collection of hot water is called a geothermal reservoir.
Hence, the super-heated steam is raised in geothermal plants by the heat of magma or lava.

State True or False :
Geothermal energy can be used to produce electricity.

  1. True

  2. False


Correct Option: A
Explanation:

The steam comes from reservoirs of hot water found a few miles or more below the earth's surface. The steam rotates a turbine that activates a generator, which produces electricity Hence Geothermal energy can be used to produce electricity.

Find the false statement from the following statements given below :-

  1. Geothermal power plants cannot operate round the clock.

  2. The initial cost in setting up Geothermal power plant will be high.

  3. Geothermal power plant uses free and renewable source of energy.

  4. Operating cost involved in a Geothermal power plant is less.


Correct Option: A
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