Consider the following statements: With increase in temperature Fermi-level tries to come in between the energy gap exactly at middle Mobility of electron in GaAs is very high compared to mobility of holeIn LED, the light energy radiated due to recom ?->(Show Answer!)

1. Consider the following statements: With increase in temperature Fermi-level tries to come in between the energy gap exactly at middle Mobility of electron in GaAs is very high compared to mobility of holeIn LED, the light energy radiated due to recombination with the aid of traps. Which of these statements are true?

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MCQ->Consider the following statements: With increase in temperature Fermi-level tries to come in between the energy gap exactly at middle Mobility of electron in GaAs is very high compared to mobility of holeIn LED, the light energy radiated due to recombination with the aid of traps. Which of these statements are true?....

MCQ-> Read the following passage carefully and answer the questions given. Certain words/phrases have been given in bold to help you locate them while answering some of the questions. From a technical and economic perspective, many assessments have highlighted the presence of cost-effective opportunities to reduce energy use in buildings. However several bodies note the significance of multiple barriers that prevent the take-up of energy efficiency measures in buildings. These include lack of awareness and concern, limited access to reliable information from trusted sources, fear about risk, disruption and other ‘transaction costs’ concerns about up-front costs and inadequate access to suitably priced finance, a lack of confidence in suppliers and technologies and the presence of split incentives between landlords and tenants. The widespread presence of these barriers led experts to predict thatwithout a concerted push from policy, two-thirds of the economically viable potential to improve energy efficiency will remain unexploited by 2035. These barriers are albatross around the neck that represent a classic market failure and a basis for governmental intervention. While these measurements focus on the technical, financial or economic barriers preventing the take-up of energy efficiency options in buildings, others emphasise the significance of the often deeply embedded social practices that shape energy use in buildings. These analyses focus not on the preferences and rationalities that might shape individual behaviours, but on the ‘entangled’ cultural practices, norms, values and routines that underpin domestic energy use. Focusing on the practice-related aspects of consumption generates very different conceptual framings and policy prescriptions than those that emerge from more traditional or mainstream perspectives. But the underlying case for government intervention to help to promote retrofit and the diffusion of more energy efficient particles is still apparent, even though the forms of intervention advocated are often very different to those that emerge from a more technical or economic perspective. Based on the recognition of the multiple barriers to change and the social, economic and environmental benefits that could be realised if they were overcome, government support for retrofit (renovating existing infrastructure to make it more energy efficient) has been widespread. Retrofit programmes have been supported and adopted in diverse forms in many setting and their ability to recruit householders and then to impact their energy use has been discussed quite extensively. Frequently, these discussions have criticised the extent to which retrofit schemes rely on incentives and the provision of new technologies to change behaviour whilst ignoring the many other factors that might limit either participation in the schemes or their impact on the behaviours and prac-tices that shape domestic energy use. These factors are obviously central to the success of retrofit schemes, but evaluations of different schemes have found that despite these they can still have significant impacts. Few experts that the best estimate of the gap between the technical potential and the actual in-situ performance of energy efficiency measures is 50%, with 35% coming from performance gaps and 15% coming from ‘comfort taking’ or direct rebound effects. They further suggest that the direct rebound effect of energy efficiency measures related to household heating is Ilkley to be less than 30% while rebound effects for various domestic energy efficiency measures vary from 5 to 15% and arise mostly from indirect effects (i.e., where savings from energy efficiency lead to increased demand for goods and services). Other analyses also note that the gap between technical potential and actual performance is likely to vary by measure, with the range extending from 0% for measures such as solar water heating to 50% for measures such as improved heating controls. And others note that levels of comfort taking are likely to vary according to the levels of consumption and fuel poverty in the sample of homes where insulation is installed, with the range extending from 30% when considering homes across all income groups to around 60% when considering only lower income homes. The scale of these gapsis significant because it materially affects the impacts of retrofit schemes and expectations and perceptions of these impacts go on to influence levels of political, financial and public support for these schemes. The literature on retrofit highlights the presence of multiple barriers to change and the need for government support, if these are to be overcome. Although much has been written on the extent to which different forms of support enable the wider take-up of domestic energy efficiency measures, behaviours and practices, various areas of contestation remain and there is still an absence of robust ex-post evidence on the extent to which these schemes actually do lead to the social, economic and environmental benefits that are widely claimed.Which of the following is most nearly the OPPOSITE in meaning to the word ‘CONCERTED’ as used in the passage ?
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MCQ-> The broad scientific understanding today is that our planet is experiencing a warming trend over and above natural and normal variations that is almost certainly due to human activities associated with large-scale manufacturing. The process began in the late 1700s with the Industrial Revolution, when manual labor, horsepower, and water power began to be replaced by or enhanced by machines. This revolution, over time, shifted Britain, Europe, and eventually North America from largely agricultural and trading societies to manufacturing ones, relying on machinery and engines rather than tools and animals.The Industrial Revolution was at heart a revolution in the use of energy and power. Its beginning is usually dated to the advent of the steam engine, which was based on the conversion of chemical energy in wood or coal to thermal energy and then to mechanical work primarily the powering of industrial machinery and steam locomotives. Coal eventually supplanted wood because, pound for pound, coal contains twice as much energy as wood (measured in BTUs, or British thermal units, per pound) and because its use helped to save what was left of the world's temperate forests. Coal was used to produce heat that went directly into industrial processes, including metallurgy, and to warm buildings, as well as to power steam engines. When crude oil came along in the mid- 1800s, still a couple of decades before electricity, it was burned, in the form of kerosene, in lamps to make light replacing whale oil. It was also used to provide heat for buildings and in manufacturing processes, and as a fuel for engines used in industry and propulsion.In short, one can say that the main forms in which humans need and use energy are for light, heat, mechanical work and motive power, and electricity which can be used to provide any of the other three, as well as to do things that none of those three can do, such as electronic communications and information processing. Since the Industrial Revolution, all these energy functions have been powered primarily, but not exclusively, by fossil fuels that emit carbon dioxide (CO2), To put it another way, the Industrial Revolution gave a whole new prominence to what Rochelle Lefkowitz, president of Pro-Media Communications and an energy buff, calls "fuels from hell" - coal, oil, and natural gas. All these fuels from hell come from underground, are exhaustible, and emit CO2 and other pollutants when they are burned for transportation, heating, and industrial use. These fuels are in contrast to what Lefkowitz calls "fuels from heaven" -wind, hydroelectric, tidal, biomass, and solar power. These all come from above ground, are endlessly renewable, and produce no harmful emissions.Meanwhile, industrialization promoted urbanization, and urbanization eventually gave birth to suburbanization. This trend, which was repeated across America, nurtured the development of the American car culture, the building of a national highway system, and a mushrooming of suburbs around American cities, which rewove the fabric of American life. Many other developed and developing countries followed the American model, with all its upsides and downsides. The result is that today we have suburbs and ribbons of highways that run in, out, and around not only America s major cities, but China's, India's, and South America's as well. And as these urban areas attract more people, the sprawl extends in every direction.All the coal, oil, and natural gas inputs for this new economic model seemed relatively cheap, relatively inexhaustible, and relatively harmless-or at least relatively easy to clean up afterward. So there wasn't much to stop the juggernaut of more people and more development and more concrete and more buildings and more cars and more coal, oil, and gas needed to build and power them. Summing it all up, Andy Karsner, the Department of Energy's assistant secretary for energy efficiency and renewable energy, once said to me: "We built a really inefficient environment with the greatest efficiency ever known to man."Beginning in the second half of the twentieth century, a scientific understanding began to emerge that an excessive accumulation of largely invisible pollutants-called greenhouse gases - was affecting the climate. The buildup of these greenhouse gases had been under way since the start of the Industrial Revolution in a place we could not see and in a form we could not touch or smell. These greenhouse gases, primarily carbon dioxide emitted from human industrial, residential, and transportation sources, were not piling up along roadsides or in rivers, in cans or empty bottles, but, rather, above our heads, in the earth's atmosphere. If the earth's atmosphere was like a blanket that helped to regulate the planet's temperature, the CO2 buildup was having the effect of thickening that blanket and making the globe warmer.Those bags of CO2 from our cars float up and stay in the atmosphere, along with bags of CO2 from power plants burning coal, oil, and gas, and bags of CO2 released from the burning and clearing of forests, which releases all the carbon stored in trees, plants, and soil. In fact, many people don't realize that deforestation in places like Indonesia and Brazil is responsible for more CO2 than all the world's cars, trucks, planes, ships, and trains combined - that is, about 20 percent of all global emissions. And when we're not tossing bags of carbon dioxide into the atmosphere, we're throwing up other greenhouse gases, like methane (CH4) released from rice farming, petroleum drilling, coal mining, animal defecation, solid waste landfill sites, and yes, even from cattle belching. Cattle belching? That's right-the striking thing about greenhouse gases is the diversity of sources that emit them. A herd of cattle belching can be worse than a highway full of Hummers. Livestock gas is very high in methane, which, like CO2, is colorless and odorless. And like CO2, methane is one of those greenhouse gases that, once released into the atmosphere, also absorb heat radiating from the earth's surface. "Molecule for molecule, methane's heat-trapping power in the atmosphere is twenty-one times stronger than carbon dioxide, the most abundant greenhouse gas.." reported Science World (January 21, 2002). “With 1.3 billion cows belching almost constantly around the world (100 million in the United States alone), it's no surprise that methane released by livestock is one of the chief global sources of the gas, according to the U.S. Environmental Protection Agency ... 'It's part of their normal digestion process,' says Tom Wirth of the EPA. 'When they chew their cud, they regurgitate [spit up] some food to rechew it, and all this gas comes out.' The average cow expels 600 liters of methane a day, climate researchers report." What is the precise scientific relationship between these expanded greenhouse gas emissions and global warming? Experts at the Pew Center on Climate Change offer a handy summary in their report "Climate Change 101. " Global average temperatures, notes the Pew study, "have experienced natural shifts throughout human history. For example; the climate of the Northern Hemisphere varied from a relatively warm period between the eleventh and fifteenth centuries to a period of cooler temperatures between the seventeenth century and the middle of the nineteenth century. However, scientists studying the rapid rise in global temperatures during the late twentieth century say that natural variability cannot account for what is happening now." The new factor is the human factor-our vastly increased emissions of carbon dioxide and other greenhouse gases from the burning of fossil fuels such as coal and oil as well as from deforestation, large-scale cattle-grazing, agriculture, and industrialization.“Scientists refer to what has been happening in the earth’s atmosphere over the past century as the ‘enhanced greenhouse effect’”, notes the Pew study. By pumping man- made greenhouse gases into the atmosphere, humans are altering the process by which naturally occurring greenhouse gases, because of their unique molecular structure, trap the sun’s heat near the earth’s surface before that heat radiates back into space."The greenhouse effect keeps the earth warm and habitable; without it, the earth's surface would be about 60 degrees Fahrenheit colder on average. Since the average temperature of the earth is about 45 degrees Fahrenheit, the natural greenhouse effect is clearly a good thing. But the enhanced greenhouse effect means even more of the sun's heat is trapped, causing global temperatures to rise. Among the many scientific studies providing clear evidence that an enhanced greenhouse effect is under way was a 2005 report from NASA's Goddard Institute for Space Studies. Using satellites, data from buoys, and computer models to study the earth's oceans, scientists concluded that more energy is being absorbed from the sun than is emitted back to space, throwing the earth's energy out of balance and warming the globe."Which of the following statements is correct? (I) Greenhouse gases are responsible for global warming. They should be eliminated to save the planet (II) CO2 is the most dangerous of the greenhouse gases. Reduction in the release of CO2 would surely bring down the temperature (III) The greenhouse effect could be traced back to the industrial revolution. But the current development and the patterns of life have enhanced their emissions (IV) Deforestation has been one of the biggest factors contributing to the emission of greenhouse gases Choose the correct option:....

MCQ-> Read the following passage carefully and answer the questions given below it. Certain words/phrases are printed in bold to help you to locate them while answering some of the questions. The outside world has pat answers concerning extremely impoverished countries, especially those in Africa. Everything comes back, again and again, to corruption and misrule. Western officials argue that Africa simply needs to behave itself better, to allow market forces to operate without interference by corrupt rulers. Ye the critics of African governance have it wrong. Politics simply can't explain Africa's prolonged economic crisis. The claim that Africa's corruption is the basic source of the problem does not withstand serious scrutiny. During the past decade I witnessed how relatively well-governed countries in Africa, such as Ghana, Malawi, Mali and Senegal, failed to prosper, whereas societies in Asia perceived to have extensive corruption, such as Bangladesh, Indonesia and Pakistan, enjoyed rapid economic growth. What is the explanation? Every situation of extreme poverty around the world contains some of its own unique causes, which need to be diagnosed as a doctor would a patient. For example, Africa is burdened with malaria like no other part of the world, simply because it is unlucky in providing the perfect conditions for that disease; high temperatures, plenty of breeding sites and particular species of malaria-transmitting mosquitoes that prefer to bite humans rather than cattle.Another myth is that the developed world already gives plenty of aid to the world's poor. Former U.S. Secretary of the Treasury, Paul O'Neil expressed a common frustration when he remarked about aid for Africa : "We've spent trillions of dollars on these problems and we have damn near nothing to show for it". O'Neil was no foe of foreign aid. Indeed, he wanted to fix the system so that more U.S. aid could be justified. But he was wrong to believe that vast flows of aid to Africa had been squandered. President Bush said in a press conference in April 2004 that as "the greatest power on the face of the earth, we have an obligation to help the spread of freedom. We have an obligation to feed the hungry". Yet how does the U.S. fulfill its obligation? U.S. aid to farmers in poor countries to help them grow more food runs at around $200 million per year, far less than $1 per person per year for the hundreds of millions of people living in subsistence farm households.From the world as a whole, the amount of aid per African per year is really very small, just $30 per sub- Saharan African in 2002. Of that modest amount, almost $5 was actually for consultants from the donor countries, more than $3 was for emergency aid, about $4 went for servicing Africa's debts and $ 5 was for debt-relief operations. The rest, about $12, went to Africa. Since the "money down the drain" argument is heard most frequently in the U.S., it's worth looking at the same calculations for U.S. aid alone. In 2002, the U.S. gave $3 per sub-Saharan African. Taking out the parts for U.S. consultants and technical cooperation, food and other emergency aid, administrative costs and debt relief, the aid per African came to grand total of 6 cents.The U.S. has promised repeatedly over the decades, as a signatory to global agreements like the Monterrey Consensus of 2002, to give a much larger proportion of its annual output, specifically upto 0.7% of GNP, to official development assistance. The U.S. failure to follow through has no political fallout domestically, of course, because not one in a million U.S. citizens even knows of statements like the Monterrey Consensus. But no one should underestimate the salience that it has around the world. Spin as American might about their nation's generosity, the poor countries are fully aware of what the U.S. is not doing.The passage seems to emphasize that the outside world has
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MCQ-> Analyse the following passage and provide appropriate answers An example of scientist who could measure without instruments is Enrico Fermi (1901-1954), a physicist who won the Nobel Prize in physics in 1938. He had a well-developed knack for intuitive, even casual-sounding measurements. One renowned example of his measurement skills was demonstrated at the first detonation of the atom bomb, the Trinity Test site, on July 16, 1945, where he was one of the atomic scientists observing the blast from base camp. While final adjustments were being made to instruments used to measure the yield of the blast, Fermi was making confetti out of a page of notebook paper. As the wind from the initial blast wave began to blow through the camp, he slowly dribbled the confetti into the air, observing how far back it was scattered by the blast (taking the farthest scattered pieces as being the peak of the pressure wave). Fermi concluded that the yield must be greater than 10 kilotons. This would have been news, since other initial observers of the blast did not know that lower limit. After much analysis of the instrument readings, the final yield estimate was determined to be 18.6 kilotons. Like Eratosthenes, Fermi was aware of a rule relating one simple observation—the scattering of confetti in the wind —to a quantity he wanted to measure. The value of quick estimates was something Fermi was familiar with throughout his career. He was famous for teaching his students skills at approximation of fanciful-sounding quantities that, at first glance, they might presume they knew nothing about. The best-known example of such a "Fermi question" was Fermi asking his students to estimate the number of piano tuners in Chicago, when no one knows the answer. His students—science and engineering majors—would begin by saying that they could not possibly know anything about such a quantity. Of course, some solutions would be to simply do a count of every piano tuner perhaps by looking up advertisements, checking with a licensing agency of some sort, and so on But Fermi was trying to teach his students how to solve problems where the ability to confirm the results would not be so easy. He wanted them to figure out that they knew something about the quantity in question.Suppose you apply the same logic as Fermi applied to confetti, which of the following statements would be the most appropriate?
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