UPSC CDS-1

21. A parallel-plate capacitor of capacitance C₁ is made using two gold pl

A parallel-plate capacitor of capacitance C₁ is made using two gold plates. Another parallel-plate capacitor of capacitance C₂ is made using two aluminium plates with same plate separation, and all the four plates are of same area. If ρg and ρa are respectively resistivities of gold and aluminium, then which one of the following relations is correct?

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”C₁
”C₂
”C₁ρa
”C₁
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The capacitance of a parallel-plate capacitor is given by the formula C = ε * (A/d), where ε is the permittivity of the dielectric material between the plates, A is the area of one plate, and d is the distance between the plates.
– The problem states that both capacitors have the same plate separation (d) and the four plates are of the same area (meaning the plates for C₁ have area A, and the plates for C₂ also have area A).
– The plates are made of gold and aluminium. These materials are conductors and form the plates; they are not the dielectric material filling the space between the plates. The dielectric material between the plates is presumably the same for both capacitors (usually air or vacuum unless specified otherwise).
– Since A, d, and the dielectric material (and thus its permittivity ε) are the same for both capacitors, their capacitances must be equal.
– The resistivities of gold (ρg) and aluminium (ρa) are properties of the plate materials themselves and do not affect the capacitance value, which is determined by the geometry of the plates and the material *between* them.
The capacitance of a capacitor depends on its physical dimensions (area and separation of plates) and the dielectric properties of the material filling the space between the plates. The conductive material of the plates affects properties like resistance and conductivity, but not the capacitance itself in the standard parallel-plate model.

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22. A copper wire of radius r and length 1 has a resistance of R. A second

A copper wire of radius r and length 1 has a resistance of R. A second copper wire with radius 2r and length 1 is taken and the two wires are joined in a parallel combination. The resultant resistance of the parallel combination of the two wires will be

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5R
5/4 R
4/5 R
R/5
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The resistance of a wire is given by the formula R = ρ * (l/A), where ρ is the resistivity of the material, l is the length, and A is the cross-sectional area. The area of a circular wire is A = πr², where r is the radius.
– For the first wire: R₁ = R = ρ * (l / πr²).
– For the second wire: The radius is 2r, and the length is l. So, R₂ = ρ * (l / π(2r)²) = ρ * (l / 4πr²) = (1/4) * [ρ * (l / πr²)] = R/4.
– When two resistors R₁ and R₂ are connected in parallel, the resultant resistance R_eq is given by 1/R_eq = 1/R₁ + 1/R₂ or R_eq = (R₁ * R₂) / (R₁ + R₂).
– Plugging in the values, R_eq = (R * (R/4)) / (R + R/4) = (R²/4) / (5R/4).
– R_eq = (R²/4) * (4/5R) = R/5.
This problem illustrates the relationship between resistance, material properties, and geometry, as well as the calculation of equivalent resistance in a parallel circuit. The resistivity (ρ) is the same for both wires as they are both copper.

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23. Consider the electromagnetic radiations having wavelengths 200 nm, 500

Consider the electromagnetic radiations having wavelengths 200 nm, 500 nm and 1000 nm. Which wavelength(s) of the following can make visual sensation to a human eye?

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200 nm and 500 nm
500 nm and 1000 nm
500 nm only
200 nm and 1000 nm
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The human eye can make a visual sensation when exposed to electromagnetic radiation within a specific range of wavelengths, known as the visible spectrum. This range is typically considered to be from about 400 nanometers (nm) to 700 nm.
– Wavelengths outside the visible spectrum (like 200 nm which is ultraviolet, and 1000 nm which is infrared) do not cause a visual sensation in humans.
– Out of the given wavelengths, only 500 nm falls within the visible spectrum (approximately 400-700 nm), corresponding to green light.
The visible spectrum is a small part of the entire electromagnetic spectrum. Different wavelengths within the visible spectrum are perceived as different colors by the human eye, ranging from violet (around 400 nm) to red (around 700 nm).

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24. The plant growth regulators are small, simple molecules of diverse che

The plant growth regulators are small, simple molecules of diverse chemical composition. They are

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carbohydrates, fats and proteins
indole compounds, adenine derivatives, carotenoids and terpenes
fatty acids, glucose and vitamins
vitamin C, vitamin D and glucose
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Plant growth regulators are small, simple molecules including indole compounds, adenine derivatives, carotenoids and terpenes.
Plant growth regulators (PGRs), also known as phytohormones, are organic compounds other than nutrients which in small amounts promote, inhibit or otherwise modify any physiological process in plants. The main classes of PGRs include Auxins (indole compounds, e.g., IAA), Cytokinins (adenine derivatives, e.g., kinetin), Gibberellins (terpenes, e.g., GA3), Abscisic Acid (carotenoid derivatives/terpenes, e.g., ABA), and Ethylene (a gaseous hormone). These chemical classifications align with the options provided.
Carbohydrates, fats, and proteins are macronutrients providing energy and building blocks. Vitamins are essential micronutrients, primarily for animal metabolism (some roles in plants are indirect). Fatty acids and glucose are basic organic molecules and metabolic intermediates, not classified as plant growth regulators in the same way as phytohormones.

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25. The mammalian heart is myogenic and it is regulated by nerves. The hea

The mammalian heart is myogenic and it is regulated by nerves. The heartbeat originates from

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sinoatrial node
QRS wave
T wave
hepatic portal system
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The heartbeat originates from the sinoatrial node.
The sinoatrial (SA) node is a specialized group of cells located in the wall of the right atrium of the heart. It is the natural pacemaker of the heart, generating electrical impulses that initiate each heartbeat. The mammalian heart’s ability to generate its own impulse is referred to as its myogenic nature.
The SA node impulse spreads through the atria, causing them to contract, and then reaches the atrioventricular (AV) node, which conducts the impulse to the ventricles. The QRS wave and T wave are graphical representations of electrical activity in the ventricles during an electrocardiogram (ECG). The hepatic portal system is part of the circulatory system involved in blood transport from the digestive organs to the liver.

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26. Kwashiorkor disease in children is caused by

Kwashiorkor disease in children is caused by

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sufficient carbohydrates but less fats in diet
sufficient carbohydrates and fats but deficient proteins in diet
sufficient vitamins but deficient fats in diet
sufficient fats but deficient vitamins in diet
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Kwashiorkor disease in children is caused by sufficient carbohydrates and fats but deficient proteins in diet.
Kwashiorkor is a form of severe protein malnutrition characterized by edema (swelling) due to fluid retention, enlarged liver with fatty infiltrates, and stunted growth. It typically affects children who are weaned onto diets that are low in protein, even if they contain adequate calories from carbohydrates and fats.
This disease is common in regions where staple foods (like grains or roots) are high in carbohydrates but low in protein. Marasmus is another form of severe malnutrition caused by deficiency in both protein and total calorie intake.

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27. Which one of the following statements with regard to volcanoes is not

Which one of the following statements with regard to volcanoes is not correct?

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Stratovolcanoes produce lava flows that initially follow valleys but are highly resistant to erosion.
The surrounding areas can remain highlands, lava ridges or mesas.
Hawaiian shield volcanoes are eroded by streams that form deeply carved valleys with steeply sloping heads.
The system of streams on a dissected volcano cone is not a radial drainage pattern.
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The statement “The system of streams on a dissected volcano cone is not a radial drainage pattern” is not correct.
Volcano cones, being elevated, roughly symmetrical peaks, naturally lend themselves to a radial drainage pattern where streams flow outwards from the central high point in all directions. When a volcano cone is dissected by erosion over time, the streams carving into its slopes typically maintain this radial arrangement.
Statements A, B, and C are generally correct regarding volcanic landforms and erosion. Stratovolcano lava flows can be resistant to erosion, creating distinct features. Erosion on large shield volcanoes like those in Hawaii does result in deeply carved valleys. The radial drainage pattern is characteristic of conical or dome-shaped landforms like volcanoes or isolated hills/mountains.

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28. Which one of the following is the correct sequence of occurrences of r

Which one of the following is the correct sequence of occurrences of rivers from Chennai to Kolkata when travelled by road (shortest distance)?

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Krishna, Kaveri, Godavari, Mahanadi, Subarnarekha
Krishna, Periyar, Godavari, Mahanadi, Subarnarekha
Penneru, Krishna, Godavari, Mahanadi, Subarnarekha
Penneru, Mahanadi, Subarnarekha, Godavari, Krishna
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The correct sequence of occurrences of rivers from Chennai to Kolkata when travelled by road along the east coast is Penneru, Krishna, Godavari, Mahanadi, Subarnarekha.
Travelling northwards from Chennai (Tamil Nadu) along the east coast through Andhra Pradesh, Odisha, and into West Bengal, the major rivers crossed in sequence are the Penneru (or Palar near Chennai), then the Krishna, followed by the Godavari, then the Mahanadi in Odisha, and finally the Subarnarekha river which forms the border between Odisha and West Bengal, before reaching Kolkata.
The Kaveri river is south of Chennai. The Periyar river flows westwards into the Arabian Sea from Kerala, not relevant for a Chennai to Kolkata eastward journey. This sequence reflects the major river systems encountered when moving north along the eastern coastal plains of India.

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29. The ratio of gross cropped area to the net sown area is called:

The ratio of gross cropped area to the net sown area is called:

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cropping intensity
intensity of crop rotation
crop productivity
cropping diversity
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The ratio of gross cropped area to the net sown area is called cropping intensity.
Gross Cropped Area (GCA) is the sum of areas under all crops sown during the year, counting area sown more than once in the same year as many times as it is sown. Net Sown Area (NSA) is the total area sown with crops only once during an agricultural year. Cropping intensity is calculated as (Gross Cropped Area / Net Sown Area) * 100. It indicates the degree of multiple cropping practiced on the same land during a year.
A higher cropping intensity implies that the same piece of land is being used for cultivation multiple times in a year, indicating more intensive land use. Crop productivity refers to the yield per unit area, while crop rotation is the practice of growing different crops sequentially on the same land to improve soil health and reduce pest buildup. Cropping diversity refers to the number and variety of crops grown in an area.

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30. In which one of the following States is Loktak Lake situated?

In which one of the following States is Loktak Lake situated?

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Sikkim
Himachal Pradesh
Manipur
Meghalaya
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Loktak Lake is situated in the State of Manipur.
Loktak Lake is the largest freshwater lake in Northeast India. It is famous for its unique floating islands, known as Phumdis, which are heterogeneous masses of vegetation, soil, and organic matter at various stages of decomposition.
Keibul Lamjao National Park, the only floating national park in the world, is located on Loktak Lake and is the last natural habitat of the endangered Sangai, the brow-antlered deer.

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