UPSC CAPF Archives

21. Electricity meter may be a/an

Electricity meter may be a/an

[amp_mcq option1=”mainframe computer” option2=”microcomputer” option3=”hybrid computer” option4=”analog computer” correct=”option4″]

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The correct option is D. An electricity meter may be an analog computer.

Traditional electromechanical electricity meters, commonly used for many years, are essentially analog devices. They measure instantaneous power (voltage multiplied by current) and integrate it over time to calculate the total energy consumed. This process of integrating a continuously varying signal (power) over time is a form of analog computation, where a physical quantity (like the rotation of a disk) represents the cumulative energy. While modern smart meters are digital and incorporate microcomputers, the question likely refers to the fundamental nature or a common type of electricity meter as a device that processes continuous electrical signals to compute energy.

Mainframe, microcomputer, and hybrid computers are classifications of general-purpose computing systems. While modern digital electricity meters contain embedded microcomputers, the *function* of measuring and integrating energy consumption, especially in older meter types, aligns with the principles of analog computation where continuous variables are processed.

22. The filament of electric bulb is generally made of tungsten because

The filament of electric bulb is generally made of tungsten because

[amp_mcq option1=”tungsten is cheap” option2=”durability of tungsten is high” option3=”light-emitting power of tungsten is high” option4=”melting point of tungsten is high” correct=”option4″]

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The correct option is D. The filament of an electric bulb is generally made of tungsten because its melting point is high.

Incandescent light bulbs produce light by heating a wire filament to a very high temperature (around 2500-3000 °C) until it glows (incandescence). Tungsten has the highest melting point of all metals (3422 °C), allowing it to withstand these extreme temperatures without melting. This property is crucial for the filament’s operation.

While tungsten is durable and emits light, its high melting point is the primary reason for its use as a filament material. Other properties like its low vapor pressure at high temperatures also contribute to its suitability, reducing evaporation and prolonging filament life compared to materials with lower melting points. Tungsten is not particularly cheap compared to common metals.

23. Transformer is used to 1. convert low a.c. voltage to high voltage

Transformer is used to

1. convert low a.c. voltage to high voltage
2. convert high a.c. voltage to low voltage
3. convert direct current to alternating current
4. regulate the fluctuation of voltage

Select the correct answer using the code given below.

[amp_mcq option1=”1 only” option2=”2 only” option3=”1 and 2″ option4=”3 and 4″ correct=”option3″]

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The correct option is C. A transformer is used to convert low a.c. voltage to high voltage and convert high a.c. voltage to low voltage.

Transformers are electrical devices that transfer electrical energy between two or more circuits through electromagnetic induction, typically to change the voltage level. A step-up transformer converts a low AC voltage to a high AC voltage (statement 1), while a step-down transformer converts a high AC voltage to a low AC voltage (statement 2). Transformers only work with alternating current (AC).

Statement 3 is incorrect; converting direct current (DC) to alternating current (AC) is done by an inverter. Statement 4 is incorrect; regulating voltage fluctuations is the function of voltage regulators or stabilizers, although transformers are part of the power distribution system where voltage levels are managed.

24. Arsenic present in groundwater can be partially removed

Arsenic present in groundwater can be partially removed

[amp_mcq option1=”along with removal of iron by precipitation/coagulation method if iron is also present in the water” option2=”on boiling even if iron is absent in the water” option3=”on UV-treatment” option4=”on filtration even if iron is absent in the water” correct=”option1″]

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The correct option is A. Arsenic present in groundwater can be partially removed along with removal of iron by precipitation/coagulation method if iron is also present in the water.

One effective method for removing arsenic from water is co-precipitation or adsorption onto iron oxyhydroxides. When iron is present in the water, or is added as a coagulant (like ferric chloride), iron precipitates are formed. Arsenic species (arsenite and arsenate) adsorb onto the surface of these precipitates or are incorporated into the growing iron particles. Subsequent sedimentation and filtration of these iron precipitates effectively remove arsenic from the water.

Other methods for arsenic removal include adsorption onto activated alumina, iron oxides, or activated carbon, ion exchange, and membrane filtration (reverse osmosis). Boiling (B), UV treatment (C), or simple filtration without precipitation (D) are not effective methods for removing dissolved arsenic from water.

25. Leaves of lotus and water lily are not easily wet because the leaves

Leaves of lotus and water lily are not easily wet because the leaves

1. have surface uneven in micro-scale and water cannot come into contact with the depressed areas due to high surface tension
2. contain an oily substance
3. contain a greasy substance
4. have surface too smooth to attract water

Select the correct answer using the code given below.

[amp_mcq option1=”1 and 3 only” option2=”3 and 4″ option3=”1 and 2 only” option4=”1, 2 and 3″ correct=”option4″]

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The correct option is D. Leaves of lotus and water lily are not easily wet because of the combined effect described in statements 1, 2, and 3.

The ‘lotus effect’ refers to the superhydrophobicity and self-cleaning property of lotus leaves. This is primarily due to the hierarchical microscopic and nanoscopic structure on the leaf surface (statement 1) combined with the presence of hydrophobic substances like epicuticular waxes (statements 2 and 3). The surface structure creates a rough texture where water droplets sit on the tips of micro-papillae, trapping air beneath them (Cassie-Baxter state). This minimizes contact area between water and the leaf surface, amplified by the low surface energy provided by the waxes (oily/greasy substances), resulting in high contact angles and low adhesion for water droplets. Statement 4 is incorrect as smoothness generally increases wetting.

Statement 1 describes the crucial structural aspect and its physical consequence (water cannot fully contact depressed areas, leading to high surface tension effects like droplet formation). Statements 2 and 3 describe the chemical composition of the coating (waxes), which are hydrophobic (water-repelling) and are typically described as oily or greasy. Both the structure and the hydrophobic coating are essential for the lotus effect.

26. ‘Turing machine’ serves as

‘Turing machine’ serves as

[amp_mcq option1=”a machine to identify explosives” option2=”an indicator to inform about forest fire” option3=”an instrument for finding out gravitational constant” option4=”a theoretical computing machine to act as an ideal model for mathematical calculation” correct=”option4″]

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The correct option is D. A Turing machine is a theoretical computing machine that serves as an ideal model for mathematical calculation.

Proposed by Alan Turing in 1936, the Turing machine is a mathematical model of computation. It defines an abstract machine that manipulates symbols on a strip of tape according to a set of rules. It is used to study the limits of computation and the concepts of algorithms and computability. It is not a physical machine designed for practical tasks like identifying explosives or measuring constants.

The Church-Turing thesis states that any algorithmic process can be simulated by a Turing machine. This makes the Turing machine a fundamental concept in computer science and the theory of computation. Modern computers are often described as being Turing-complete, meaning they can perform any computation that a universal Turing machine can.

27. Diamond Ring, God’s Eye and Baily’s Beads are the parts of which one a

Diamond Ring, God’s Eye and Baily’s Beads are the parts of which one among the following natural phenomena?

[amp_mcq option1=”Solar eclipse” option2=”Aurora” option3=”Lightning” option4=”Solar storm” correct=”option1″]

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The correct option is A. Diamond Ring, God’s Eye, and Baily’s Beads are phenomena observed during a solar eclipse.

During a total solar eclipse, as the Moon nearly completely covers the Sun, the last few drops of sunlight streaming through the valleys on the Moon’s limb create points of light known as Baily’s Beads. Just before totality, when only one bright spot remains, it creates a dazzling effect resembling a diamond ring on the Sun’s corona. ‘God’s Eye’ is sometimes used informally to describe the overall appearance of the corona during a total solar eclipse.

These phenomena are transient and depend on the alignment of the Sun, Moon, and Earth during an eclipse. They are celebrated sights for observers of total solar eclipses. Auroras are atmospheric light displays caused by charged particles from the Sun interacting with Earth’s magnetic field. Lightning is an electrical discharge during thunderstorms. Solar storms are eruptions of energy from the Sun.

28. The three primary soil micro-nutrients are

The three primary soil micro-nutrients are

[amp_mcq option1=”carbon, oxygen and water” option2=”copper, cadmium and carbon” option3=”nitrogen, phosphorus and potassium” option4=”boron, zinc and magnesium” correct=”option3″]

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The correct option is C. Nitrogen, Phosphorus, and Potassium are the three primary macronutrients required by plants.

Plants require various nutrients from the soil for healthy growth. These are broadly classified into macronutrients (needed in larger quantities) and micronutrients (needed in smaller quantities). The three most crucial macronutrients, often called primary nutrients, are Nitrogen (N), Phosphorus (P), and Potassium (K). While the question asks for “micro-nutrients”, option C lists the standard “primary” nutrients. Given the options, NPK is the only plausible set of primary nutrients listed.

Other macronutrients include Calcium (Ca), Magnesium (Mg), and Sulfur (S). Micronutrients include Iron (Fe), Manganese (Mn), Zinc (Zn), Copper (Cu), Boron (B), Molybdenum (Mo), and Chlorine (Cl). Option D lists some micronutrients, but NPK are universally referred to as the primary nutrients. The question’s wording “primary soil micro-nutrients” might be slightly imprecise, potentially intending to ask for primary nutrients or listing common soil nutrients from which to choose the primary ones. In the context of soil fertility and fertilizers, NPK are the standard primary nutrients.

29. Diamond is a polymorph of graphite. Both contain carbon atoms, but the

Diamond is a polymorph of graphite. Both contain carbon atoms, but they have extremely different properties because of the condition in which they are formed. Diamond is obtained after applying

[amp_mcq option1=”very high pressure and low temperature” option2=”very low pressure and high temperature” option3=”very low pressure and low temperature” option4=”very high pressure and high temperature” correct=”option4″]

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The correct option is D. Diamond is formed under conditions of very high pressure and high temperature deep within the Earth’s mantle.

Diamond and graphite are both allotropes (polymorphs) of carbon. Their dramatically different properties (hardness, electrical conductivity, etc.) arise from their different crystal structures, which are formed under vastly different pressure and temperature conditions. Graphite is the stable form of carbon at standard conditions, while diamond is stable only at extremely high pressures and temperatures.

Natural diamonds are formed at depths of 140 to 190 kilometers (87 to 118 miles) in the Earth’s mantle, where pressures are between 45 and 60 kilobars and temperatures are between 900 and 1,300 degrees Celsius (1,650 to 2,370 degrees Fahrenheit). Synthetic diamonds are also created using high-pressure high-temperature (HPHT) or chemical vapor deposition (CVD) methods, simulating similar extreme conditions.

30. Natural gas is a mixture of gases and contains mainly

Natural gas is a mixture of gases and contains mainly

[amp_mcq option1=”methane and higher hydro-carbons” option2=”butane and isobutene” option3=”methane only” option4=”methane, hydrogen and carbon monoxide” correct=”option1″]

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Natural gas is a naturally occurring hydrocarbon gas mixture. The primary component of natural gas is methane (CH₄), which is the simplest hydrocarbon molecule. However, natural gas is typically not pure methane. It also contains varying amounts of other, heavier gaseous hydrocarbons such as ethane (C₂H₆), propane (C₃H₈), butane (C₄H₁₀), and pentane (C₅H₁₂), commonly referred to as higher hydrocarbons or natural gas liquids (NGLs). In addition to hydrocarbons, natural gas can contain non-hydrocarbon gases such as carbon dioxide (CO₂), nitrogen (N₂), hydrogen sulfide (H₂S), and trace amounts of other gases like helium. The question asks for the main components. While methane is the most abundant component, “methane and higher hydro-carbons” accurately describes the primary composition.

Natural gas is a mixture, predominantly methane, but also containing other light hydrocarbons.

The exact composition of natural gas varies depending on the source (gas field). Raw natural gas must be processed to remove impurities and heavier hydrocarbons before it can be distributed and used as fuel. The higher hydrocarbons are often separated and sold as valuable byproducts (NGLs).