Non-conventional Sources of Energy Questions in English

(N/A) Obtaining energy from nuclear fusion reactions is preferable to obtaining energy from nuclear fission reactions for the following reasons:
$(i)$ For a given mass of fuel,the energy released during nuclear fusion is significantly greater than the energy released during nuclear fission.
$(ii)$ Nuclear fission produces radioactive waste,which poses a significant challenge for safe disposal and long-term storage. In contrast,nuclear fusion does not produce such hazardous radioactive waste,making it a cleaner and safer alternative.

(N/A) Solar energy is stored in the oceans in the forms of $Ocean \ Thermal \ Energy$ $(OTE)$,$Wave \ Energy$,and $Tidal \ Energy$.
Two forms that can be harnessed to obtain energy in a usable form are:
$1$. $Ocean \ Thermal \ Energy$ $(OTE)$: This is harnessed by utilizing the temperature difference between the warm surface water and the cold deep water to run turbines for electricity generation.
$2$. $Wave \ Energy$: This is harnessed by using the kinetic energy of waves to move floating devices or air columns,which in turn drive turbines to generate electricity.

(N/A) Obtaining energy from nuclear fusion reactions is preferable to obtaining energy from nuclear fission reactions for the following reasons:
$(i)$ For a given mass of fuel,the energy released from nuclear fusion is significantly larger than the energy released from nuclear fission.
$(ii)$ Nuclear fission produces radioactive waste,which poses a major challenge for safe disposal and environmental protection. In contrast,nuclear fusion does not produce such hazardous radioactive waste,making it a cleaner energy source.

(N/A) nuclear fusion reaction is a process in which two or more lighter atomic nuclei combine to form a single,heavier nucleus,accompanied by the release of a significant amount of energy.
The conditions required for a nuclear fusion reaction to occur are:
$(i)$ The temperature of the fusing nuclei must be extremely high,typically around $10^{7} \, K$,to overcome the electrostatic repulsion between the positively charged nuclei.
$(ii)$ The nuclei must be accelerated to very high speeds,often using particle accelerators or by creating high-pressure environments,to ensure they collide with sufficient kinetic energy to fuse.

(N/A) The general principle involved in generating nuclear energy is nuclear fission. In this process, a heavy nucleus, such as $Uranium-235$ or $Plutonium-239$, is bombarded with slow-moving neutrons, causing it to split into smaller, lighter nuclei while releasing a tremendous amount of energy.
One common fuel used in a nuclear reactor is $Uranium-235$ $(U-235)$.

(N/A) Ocean thermal energy refers to the energy available due to the temperature difference between the water at the surface of the ocean and the water at deeper levels.
Due to sunlight,the water at the surface of the sea gets heated up,while the water in the deeper regions remains relatively cold.
This temperature difference is utilized to generate electricity.
The warm surface water is used to boil a volatile liquid like ammonia.
The high-pressure vapours of the liquid are then used to run the turbine of a generator,which produces electricity.

(N/A) Geothermal energy is harnessed through the following steps:
$1$. Molten rocks from the deeper parts of the Earth's crust are pushed upwards and trapped in specific regions known as $hot \text{ } spots$.
$2$. Underground water that comes into contact with these $hot \text{ } spots$ gets heated and turns into high-pressure steam.
$3$. This steam is then routed through pipes to the surface, where it is used to rotate the turbines of an electric generator, thereby producing electricity.

(N/A) $1$. Environment friendly: Wind energy is a clean source of energy that does not produce harmful greenhouse gases or pollutants during operation.
$2$. No recurring expenditure: Once the wind turbine is installed,the source of energy (wind) is free,leading to no recurring fuel costs.
$3$. Renewable source: Wind is a natural,inexhaustible source of energy that will not run out over time.

(N/A) wind energy farm consists of a number of windmills erected over a large area such that the energy output of each mill in the farm is coupled together.
Steps involved in generating electricity:
$1$. The kinetic energy of the wind is used to rotate the blades of the windmills.
$2$. The rotatory motion of the windmill is used to turn the turbine of an electric generator.
$3$. The energy output of each individual windmill in the farm is coupled together to generate electricity on a commercial scale.

(N/A) Advantages:
$(i)$ It is used to propel sailboats.
$(ii)$ It is used to drive windmills which further operate water-lifting pumps and flour mills.
$(iii)$ Aeroplanes use this energy for their upward and downward movements.
$(iv)$ It is used for flying engineless aeroplanes called gliders and for generating electricity.
$(v)$ It is a renewable source,free of cost,and does not cause any pollution.
Limitations:
$(i)$ Windmills produce less energy compared to other conventional forms of energy production.
$(ii)$ They are totally dependent on wind,which may not be available at all times or in all locations.
$(iii)$ Windmills are large,bulky,and inconvenient to install and maintain compared to other energy forms.

(N/A) The following factors prevent the use of solar cell panels to meet all our domestic needs for electricity:
$(i)$ High cost of installation.
$(ii)$ Limited availability of special grade silicon required to manufacture solar cells.
$(iii)$ The technology required to obtain high-purity silicon is extremely expensive.
$(iv)$ High cost of materials,such as silver,used for interconnecting solar cells in a panel.
$(v)$ Lack of efficient and affordable systems to store the electrical energy generated by solar panels.

(N/A) The process of obtaining biogas involves the following steps:
$1$. $A$ slurry of animal dung (e.g.,cow dung) and water is prepared in a mixing tank.
$2$. This slurry is fed into a digester,which is a sealed,underground tank made of bricks.
$3$. Inside the digester,anaerobic microorganisms break down the complex organic compounds present in the biomass.
$4$. This process occurs in the absence of oxygen and produces gases like methane $(CH_4)$,carbon dioxide $(CO_2)$,hydrogen $(H_2)$,and hydrogen sulphide $(H_2S)$.
$5$. The resulting mixture,known as biogas,is collected and supplied to consumers through pipes.
Anaerobic decomposition is the process where microorganisms (anaerobic bacteria) decompose complex organic matter such as carbohydrates,proteins,and fats present in animal and plant wastes into simpler substances like methane gas,in the presence of water but in the complete absence of oxygen.

(N/A) The three forms of energy from the oceans are:
$(i)$ Tidal energy
$(ii)$ Ocean wave energy
$(iii)$ Ocean thermal energy
Ocean Thermal Energy Conversion $(OTEC)$ power plants are facilities designed to harness the temperature difference between the warm surface water of the ocean and the cold water at deeper levels to generate electricity.
Operation:
$1$. In an $OTEC$ power plant,the warm surface water of the ocean is used to boil a volatile liquid like ammonia.
$2$. The high-pressure vapours of this liquid are then used to drive turbines,which in turn rotate generators to produce electricity.
$3$. The cold sea water from deeper levels is pumped up to condense the vapours back into a liquid,which is then recycled.
$4$. This system can operate continuously for $24$ hours a day.

(N/A) The principal advantages of solar cells are as follows:
$1$. They have no moving parts,which reduces wear and tear.
$2$. They require very little maintenance.
$3$. They work satisfactorily without the use of any focusing device.
$4$. They can be set up in remote,inaccessible,or sparsely populated areas where laying power transmission lines is expensive and not commercially viable.

(N/A) In a process called nuclear fission,the nucleus of a heavy atom,such as $U^{235}$,is bombarded with low-energy neutrons,causing it to split into lighter nuclei.
During this process,a tremendous amount of energy is released due to the mass defect.
This released heat energy is used to boil water to produce high-pressure steam.
This steam is then used to drive a turbine,which is connected to an electrical generator (dynamo),thereby converting mechanical energy into electrical energy.

(N/A) Construction: $A$ solar water heater consists of an insulated metallic box painted black from both inside and outside. Inside this box,copper tubes,also painted black,are fitted in a zigzag pattern. The black color is used to absorb the maximum radiant heat energy from the sun. The box is covered with a glass sheet lid to trap sunrays by producing a greenhouse effect. The two ends of the copper tubes are connected to a water storage tank as shown in the diagram. The entire setup is placed on the roof of a building to ensure maximum exposure to sunlight.
Working: When sunlight falls on the solar heater,the radiant heat energy enters the metal box through the glass lid and is absorbed by the water flowing through the copper tubes. As the water gets heated,it expands and becomes less dense,causing it to rise and flow into the storage tank through the upper tube $(R)$. Simultaneously,fresh cold water from the bottom of the storage tank flows into the copper tubes through the lower tube $(Q)$ to replace the heated water. This continuous circulation of water between the solar heater box and the insulated storage tank continues as long as there is sunshine. The hot water stored in the tank can then be drawn out for use through the tap attached to the pipe.

(N/A) Ram's father explained that hot springs are formed when hot underground water finds an outlet at the surface and emerges from the earth.
$(b)$ Geothermal energy is not generated on a large scale because there are very few commercially viable sites where geothermal energy can be effectively exploited.
$(c)$ The main advantage of using geothermal energy is that it is a non-conventional,renewable source of energy that can be harnessed continuously for $24$ hours throughout the year.

(N/A) The reasons for the inefficient working of the solar cooker could be as follows:
$(i)$ The inner surface of the box might not have been painted black to absorb maximum solar radiation.
$(ii)$ The box might not have been properly insulated,leading to heat loss.
$(iii)$ The reflector might not be positioned at the correct angle to direct sunlight into the box.
$(iv)$ The glass cover might be too thin or not airtight,allowing heat to escape.
Ordinarily,the maximum temperature that can be reached inside a box-type solar cooker ranges between $100^{\circ}C$ and $140^{\circ}C$.

(N/A) Biogas plants are considered to be a boon to farmers for the following reasons:
$(i)$ Farmers obtain a clean fuel that produces no smoke or harmful emissions compared to traditional dried dung cakes.
$(ii)$ The spent slurry,which is the residue left after biogas extraction,serves as an excellent source of organic manure. This manure is produced quickly and can be applied directly to fields,unlike traditional composting methods.
$(iii)$ Biogas plants decompose various organic waste materials that would otherwise cause pollution. This process effectively helps in managing waste and controlling environmental pollution.

(N/A) Biogas is considered an ideal fuel for the following reasons:
$(i)$ It has a high calorific value, providing efficient energy.
$(ii)$ It burns without producing smoke, ensuring clean combustion.
$(iii)$ It has a moderate ignition temperature, making it safe to handle.
$(iv)$ It does not produce harmful residues or toxic gases upon combustion.
$(v)$ It is cost-effective and easily accessible, especially in rural areas.
Due to these characteristics:
$(i)$ Biogas acts as an excellent fuel source, thereby addressing the fuel crisis.
$(ii)$ Since it does not cause air pollution, it helps solve environmental problems.
$(iii)$ The use of animal waste and organic matter in biogas plants prevents water pollution and promotes waste management.

(C) Renewable sources of energy are those that are naturally replenished on a human timescale,such as sunlight,wind,and geothermal heat.
$A$. Coal is a fossil fuel and is non-renewable.
$B$. Uranium is a finite mineral resource used in nuclear energy and is non-renewable.
$C$. Geothermal power is derived from the internal heat of the Earth,which is continuously generated and thus considered a renewable source.
$D$. Natural gas is a fossil fuel and is non-renewable.
Therefore,the correct option is $C$.

(C) Ocean Thermal Energy Conversion $(OTEC)$ systems utilize the temperature difference between the warm surface water of the ocean and the cold deep-sea water.
For the efficient operation of an $OTEC$ power plant,a temperature difference of at least $20^{\circ} C$ between the surface water and the water at depths up to $1000 \,m$ is required.
This temperature gradient allows the system to drive a heat engine to produce electricity.

(A) Nuclear fission is a process in which the nucleus of a heavy atom,such as uranium,is split into two or more smaller nuclei when bombarded with neutrons.
During the fission of a single uranium-$235$ $(^{235}U)$ atom,a significant amount of energy is released due to the mass defect between the reactants and the products.
This energy is approximately $200\,MeV$ (mega-electron volts) per fission event.
Therefore,the correct option is $A$.

(TRUE) The statement is True.
Solar energy is considered to have the greatest potential among all renewable energy sources because the amount of solar energy reaching the Earth's surface in a single hour is more than the entire world's energy consumption for a whole year. It is abundant,inexhaustible,and widely available across the globe.

(TRUE) True.
Solar cells,also known as photovoltaic cells,are devices that convert light energy directly into electricity using the photovoltaic effect. These cells are primarily constructed from semiconductor materials,most commonly silicon,which possess the unique property of generating an electric current when exposed to light.

(B) The statement is False.
Modern commercial silicon-based solar cells typically have an efficiency ranging from $15 \%$ to $20 \%$.
Selenium solar cells,which were among the earliest types developed,have a much lower efficiency,typically less than $1 \%$.
Therefore,the claim that a selenium solar cell can convert $25 \%$ of sunlight into electrical energy is incorrect.

(FALSE) The statement is False.
Solar cells and solar panels are highly effective in remote areas where conventional electricity grids are difficult or expensive to install. They provide a reliable and sustainable source of energy for lighting,water pumping,and communication in off-grid locations.

(D) An eco-friendly activity is one that does not harm the environment or contributes to sustainable development.
$A$. Using a car for transportation increases carbon emissions,which contributes to global warming.
$B$. Using polybags (plastic bags) is harmful because they are non-biodegradable and cause pollution.
$C$. Using chemical dyes for colouring clothes often leads to water pollution as these chemicals are released into water bodies.
$D$. Using windmills to generate power for irrigation is an eco-friendly activity because it utilizes renewable wind energy,which does not cause pollution or deplete natural resources.