What is a Good Source of Energy Questions in English

(N/A) $(i)$ Renewable sources of energy can be replenished naturally over a short period and can be used repeatedly,e.g.,wind energy. On the other hand,non-renewable sources of energy cannot be replenished once consumed and get exhausted over time,e.g.,coal.
$(ii)$ The use of wood as a fuel is not advised because the natural replenishment of forests is an extremely slow process compared to the rate of consumption. Furthermore,wood has a low calorific value,its burning causes significant air pollution,and it produces large amounts of ash,which creates disposal problems.

(N/A) $(i)$ Burning biomass directly in traditional ovens (chulhas) is discouraged because it is less efficient,produces a lot of smoke,and causes significant air pollution.
$(ii)$ Using biomass to produce biogas is encouraged because it is a highly efficient fuel,burns without smoke,and the spent slurry left behind in the biogas plant serves as an excellent,nutrient-rich manure for crops.

(N/A) Hydrogen is considered a cleaner fuel because,upon combustion,it produces only water vapour $(H_2O)$,which is non-polluting and environmentally friendly.
In contrast,$CNG$ (Compressed Natural Gas) is a hydrocarbon fuel that releases carbon dioxide $(CO_2)$ and other trace pollutants when burned.
Although hydrogen is cleaner,its widespread use is currently limited due to its highly explosive nature,as well as significant challenges related to its storage and transportation.

(N/A) Charcoal is obtained by burning wood in a limited supply of oxygen (a process known as destructive distillation).
$(b)$ Charcoal is considered a better fuel than wood because:
$(i)$ It burns without producing a flame.
$(ii)$ It produces very little or no smoke compared to wood.
$(iii)$ It has a higher calorific value (heat-generating efficiency) than wood.

(N/A) The heat energy from solar radiation causes the evaporation of surface water.
These vapours,after condensation,return to the Earth as rain or snowfall,which eventually forms running water in rivers.
Additionally,solar heat radiation causes the melting of ice on mountains,which also contributes to the flow of water.
The kinetic energy of this flowing water is harnessed to rotate turbines for generating electricity.
Therefore,hydroelectricity is considered an indirect form of solar energy.

(C) non-renewable source of energy is a natural resource that cannot be readily replaced by natural means at a pace quick enough to keep up with consumption. Examples include fossil fuels like coal,petroleum,and natural gas.
Wood is considered a renewable source of energy because it can be replenished by planting new trees within a relatively short period of time compared to the geological timescales required for fossil fuel formation.
Therefore,wood is not a non-renewable source of energy.

(D) The Earth receives only a very small fraction of the total energy radiated by the Sun.
According to scientific estimates,the Earth intercepts approximately $47 \%$ of the solar energy that reaches the outer atmosphere,while the rest is either reflected back into space by clouds and dust or absorbed by the atmosphere.
Therefore,the correct fraction is approximately $47 \%$.

(A) The sun generates energy through the process of nuclear fusion.
In this process,light atomic nuclei,primarily $Hydrogen$ isotopes,fuse together to form heavier nuclei,such as $Helium$.
$Hydrogen$ acts as the primary nuclear fuel for the sun,providing the necessary mass to sustain the fusion reaction that releases immense amounts of energy.

(B) functional windmill requires a minimum wind speed to overcome the inertia of the blades and generate useful mechanical or electrical energy.
According to standard scientific data and textbooks,the minimum wind velocity required for a functional windmill is approximately $15 \, km h^{-1}$.
Wind speeds below this threshold are generally insufficient to rotate the turbine blades effectively for power generation.

(D) The calorific value of a fuel is the amount of heat energy produced on complete combustion of $1 \, kg$ (or $1 \, g$) of a fuel.
For wood,the calorific value ranges from approximately $17 \, kJ/g$ to $22 \, kJ/g$.
Among the given options,$17 \, kJ/g$ is the standard value typically cited in textbooks for wood.

(B) Charcoal is a form of carbon. The combustion of carbon releases energy in the form of heat.
The calorific value of charcoal is approximately $33 \,kJ/g$.
Therefore,burning $1 \,g$ of charcoal liberates about $33 \,kJ$ of energy.

(C) Fossil fuels are natural fuels formed from the remains of living organisms buried under the Earth's surface over millions of years. Examples include $Coal$, $Petroleum$, and $Natural \ gas$.
$Wood$ is a biomass fuel obtained from trees and is not formed through the fossilization process.
$Biogas$ is a mixture of gases produced by the breakdown of organic matter in the absence of oxygen, which is also not a fossil fuel.
However, in the context of standard multiple-choice questions regarding non-fossil fuels, $Wood$ and $Biogas$ are both correct. Given the options, $Wood$ is the most traditional example of a non-fossil fuel (biomass) often contrasted with fossil fuels in textbooks.

(TRUE) True.
Solar heating devices,such as solar cookers and solar water heaters,often utilize concave mirrors or polished surfaces as reflectors. These reflectors concentrate the incoming solar radiation onto a specific point or area,thereby increasing the intensity of heat and improving the efficiency of the device.

(FALSE) The statement is False.
Explanation: Glass is transparent to visible light and infrared radiation (heat),but it is opaque to ultraviolet $(UV)$ radiation. The glass cover of a solar cooker allows short-wavelength visible light to enter,which is then absorbed by the black interior and converted into heat (infrared radiation). This heat is trapped inside because glass does not allow long-wavelength infrared radiation to escape easily (the greenhouse effect). It does not allow $UV$ radiation to pass through.

(B) Fossil fuels are natural resources formed from the remains of ancient plants and animals over millions of years,such as coal,petroleum,and natural gas.
$A$. Wind,ocean,and coal: Coal is a fossil fuel.
$B$. Wind,wood,and sun: None of these are fossil fuels. Wind and sun are renewable energy sources,and wood is a biomass fuel.
$C$. Kerosene,wind,and tide: Kerosene is a product derived from petroleum (a fossil fuel).
$D$. Petroleum,wood,and sun: Petroleum is a fossil fuel.
Therefore,the correct combination is wind,wood,and sun.

(D) The calorific value of a fuel is the amount of heat energy produced by the complete combustion of $1 \ kg$ of that fuel.
- The calorific value of $CH_4$ (Methane) is approximately $50,000 \ kJ/kg$.
- The calorific value of $C_4H_{10}$ (Butane) is approximately $50,000 \ kJ/kg$.
- The calorific value of Water gas $(CO + H_2)$ is approximately $15,000 \ kJ/kg$.
- The calorific value of $H_2$ (Dihydrogen gas) is approximately $150,000 \ kJ/kg$.
Therefore,$H_2$ (Dihydrogen gas) has the highest calorific value among the given options.

(C) Dihydrogen $(H_2)$ is considered a potential major energy source for the future.
$1$. It is an environmentally friendly fuel because its combustion produces only water $(H_2O)$ as a byproduct,resulting in zero carbon emissions.
$2$. It has a very high energy content per unit mass compared to conventional fossil fuels.
$3$. As fossil fuel reserves are depleting and causing climate change,$H_2$ is being researched as a sustainable alternative.