CULTURAL QA 05-2023-29A Q1 Why do we use AC but not DC inhouseholds?
A1 Info Sage, Former InsightInvestigator (2018–2022) May 22 Why we use AC(alternating current) instead of DC (direct current) in households in a simpleand understandable way. Here are the reasons: 1. Efficient Generation and Transmission: ACis more efficient for generating and transmitting electricity over longdistances. It can be easily transformed to differentvoltage levels using transformers, which allows for efficient transmission overpower lines. This is essential for delivering electricity from power plants tohomes and businesses located far away. 2. Safety: AC electricity is safer to use in householdscompared to high-voltage DC. In the early days of electricity, itwas discovered that AC can be easily transformed to lower voltages, making itsafer for human contact. This led to the development of distribution systemsusing AC, as it reduced the risk of electrical shock and electrocution. 3. Voltage Regulation: AC can be easilyregulated and controlled using transformers and voltage regulators.This allows for adjustments in voltage levels, which is important for matchingthe varying power requirements of different devices in a household. It enablesthe use of different appliances with varying voltage needs without the need forindividual power supplies. 4. Compatibility: Many appliances and devices aredesigned to operate on AC power. AC is the standard form of electrical powersupplied to homes and businesses, and most electrical appliances, suchas lights, refrigerators, televisions, and air conditioners, are designed torun on AC power. Switching to DC would require significant changes ininfrastructure and the development of new DC-compatible devices. 5. Power Transmission Grid: The existing powertransmission and distribution infrastructure, including power grids andsubstations, are designed for AC power. Replacing the entire infrastructurewith DC systems would be costly and impractical. Q2 What is the best time to eat guava? A2 Debasish, Health and Fitness expert -Since 20128h There isn'ta specific "best" time to eat guava that applies to everyone,as it ultimately depends on personal preferences and dietary needs. Guava is anutritious fruit that can be enjoyed at different times of the day based onindividual preferences. Here are a few suggestions: Breakfast: Guava can be a great addition to yourbreakfast. You can enjoy it as a standalone fruit or incorporate it intosmoothies, yogurt bowls, or cereal. Snack: Guava makes for a refreshing and healthysnack option. You can have it during mid-morning or afternoon to satisfy hungerand provide a boost of energy. Pre-workout: The natural sugars and carbohydratesin guava can provide a quick source of energy. Eating guava before a workoutcan be beneficial, but make sure to give yourself enough time to digest beforeexercising. Dessert: Guava's sweet and tangy flavour makes ita delicious choice for desserts. You can use it in fruit salads, tarts, or evenmake guava jelly. Ultimately,you can enjoy guava whenever it suits your taste and fits well into your dailyroutine. It's important to note that guava is high in fibre,so eating it in moderation and balancing it with other nutritious foods isrecommended. Q3 Can a Boeing 747 be flown by onepilot? A3 Vishnu Ravi, Aviation Enthusiast |Content Creator Sat Certain small business jets have the potential to bepiloted by a sole individual. Nevertheless, when it comes to commercial jetsresponsible for transporting passengers and cargo, a minimum of two pilots isrequired. Some airlines andmanufacturers have raised the concept of a single pilot in the cockpit ofcommercial aircraft, but it has yet to receive regulatory approval. The presence of two fully qualifiedand experienced pilots in each cockpit holds the utmost importance for ensuringsafety. In relation to theBoeing 747, it is not designed to operate with just one engine, although it cansustain flight on a single engine for approximately three hours in the event ofan emergency, enabling it to reach the nearest airport. However, flying a 747 with only oneengine is not advisable, as the aircraft is not engineered to be flown by alone pilot. It is essential tounderstand that aircraft receive certification for operation with a specificcrew size, and there are jets certified for single-pilot operations. However,this certification does not extend to commercial jets carrying passengers andcargo, as they necessitate a minimum of two pilots in the cockpit for safetyconsiderations. To sum up, a Boeing 747 cannot be piloted by a singleindividual, and commercial jets responsible for carrying passengers and cargorequire a minimum of two pilots in the cockpit. Whilecertain small business jets can be operated by a lone pilot, the concept of asingle pilot in the cockpit of commercial aircraft has yet to gain regulatoryapproval. Q4 Why only a DC voltage is current usedto run a train? A4 Mani. P, Manager at Jarmaaks Softtex DC (direct current)voltage is commonly used to power trains because of several advantages itoffers over AC (alternating current) voltage. Here are some reasons why DCvoltage is preferred for train systems: Simplicity of motor design: DC motors are simpler and more efficientcompared to AC motors, especially at low speeds. Trainsrequire high starting torques and frequent speed control, and DC motors canprovide smooth acceleration and deceleration with precise control. Regenerative braking: DC systems allow for efficient regenerative braking,where the kinetic energy of the moving train is converted back into electricalenergy and fed back into the power supply. This energy can be reused by othertrains on the same line, reducing overall energy consumption and improvingefficiency. Power distribution: DC power distribution is morestraightforward and easier to control compared to AC systems. DC voltages are typically used forthird rail or overhead wire systems, where the power is supplied directly tothe train. AC power, on the other hand, requires complexsubstations andtransformers for voltage conversion, which adds complexity and cost to theinfrastructure. Compatibility with other systems: Manyauxiliary systems in trains, such as lighting, air conditioning, and controlcircuits, operate on DC voltage. By using a DC power supplyfor propulsion, it becomes easier to integrate and power these auxiliarysystems directly without the need for additional conversion devices. It's worthnoting that some modern train systems, especially high-speed trains, use acombination of AC and DC voltage. AC voltageis used for long-distance transmission and is converted to DC for propulsion.This hybrid approach allows for efficient power transmission over longdistances while benefiting from the advantages of DC motors for propulsion andcontrol. Q5 Why does an airplane need fullthrottle for take-off but right after it the pilot "slows" it down? A5 Srinidhi Kulkarni, Working as anengineer for 11 + years5h During take-off, power is needed to overcome air drag,frictional force from the ground (rolling resistance of the tires) and theforce needed to accelerate the aircraft to the required high speeds (whichgives enough air flow over the wings to generate lift). During steady flight, power is needed to only overcome airdragand maintain air speed. No frictional forces, no forces needed foracceleration. All the above QA arefrom Quora website on 28--05- 2023. Quora answers need not be 100% correct answers. Q6 Where did modern humans come from? A6 New study adds twist to theory of ourevolution A new study has now introduced a new twist in the tale ofevolution as scientists propose that modern humans descendedfrom two populations. New Delhi, UPDATED:May 19, 2023 18:55 IST Human evolution The research indicated that multiple ancestral groups fromacross Africa contributed to the emergence of Homo sapiens.Study taps into genome data from modern-day African populations. The findingsdid not support a longstanding hypothesis. Multiple groups from across Africacontributed to emergence of Homo sapiens By India Today Science Desk: Where did modernhumans come from? The question is key to the study of evolution and it wasbelieved that we all had our humble origins from a single group of ancestorsthat came out of Africa, until now. A new study has now introduced a new twist in the taleof evolution as scientists propose that modern humans descended from twopopulations that lived in Africa for a million years individually beforemerging across the continent, indicating that there is no single birthplace ofhumanity. It taps into genomedata from modern-day African populations, offering insight into how this mayhave unfolded. The study published in the journal Nature states thatdespite broad agreement that Homo sapiens originated in Africa,considerable uncertainty surrounds specific models of divergence and migrationacross the continent. Evolution It has been long held that modern humans sprang acrossthe world from Africa. (Photo: Getty) "Decades ofstudy of human genome variation have suggested a predominantly tree-like model of recent populationdivergence from a single ancestral population in Africa. t has beendifficult to reconcile this finding with the fossil and archaeological recordsof human occupation across the vast African continent," researchers saidin the paper. The global team of researchers from differentinstitutions analysed the genomes of 290 living people and conductedlarge-scale simulations of human history feeding multiple scenarios ofdifferent populations existing in Africa to the softwarewhich could produce the diversity of DNA found in people living today. The research indicated that multiple ancestral groupsfrom across Africa contributed to the emergence of Homo sapiens in a patchworkmanner,migrating from one region to another and mixing with one another over hundredsof thousands of years. The team analysedDNA from different groups arising in Africa from Mende, farmers living inSierra Leone in West Africa to the Gumuz, a group descended fromhunter-gatherers in Ethiopia; the Amhara, a group of Ethiopian farmers; and theNama, a group of hunter-gatherers in South Africa, the New York Times reported. Neandrathal The team looked at50,000-year-old Neanderthal found in Croatia, another close relative of ancienthumans. It has long beenheld that modern humans sprang across the world from Africa as the oldestfossil was unearthed on the continent. The fossil was 3,00,000 years old and archeologists havealso found the oldest stone tools from the region as well, hinting at some sortof human settlement. The team comparedthe DNA of African people in the study with that of a person from Britain andthe genome of a 50,000-year-old Neanderthal found in Croatia, another closerelative of ancient humans. Theyconcluded that the ancestors of our species existed in two different populationgroups dubbed Stem1 and Stem2 by the team led by Dr. Brenna Henn, a geneticistat the University of California, Davis. It alsofound that everyone alive today can trace their ancestry to at least twodistinct populations that were present in Africa dating back about a millionyears. "All humansshare a relatively recent common ancestry, but the story in the deeper past ismore complicated than our species evolving in just a single location or inisolation," said University of Wisconsin-Madison population geneticistAaron Ragsdale, lead author of the study. The ancestralgroups were likely spread across a geographic landscape in a population structurethat, Ragsdale said, "was 'weak,' meaning that there was ongoing or atleast recurrent migration between groups, and this maintained geneticsimilarity across ancestral populations." The fossil recordis scanty in the time period that would be most informative about the emergenceand spread of Homo sapiens, and there is no ancient DNA from skeletal or dentalremains from these time periods, the researchers said. The above QA is based on the front page article in yahooopening page on 29-5-23. Compiled andposted by R. Gopala Krishnan, former ITS, on 29-05-2023 -- You received this message because you are subscribed to the Google Groups "Thatha_Patty" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/thatha_patty/2006021540.2450065.1685327421981%40mail.yahoo.com.
