UPSC NDA-2 Archives

31. Which of the following statements about the technological innovations

Which of the following statements about the technological innovations during the Industrial Revolutions are correct ?

1. Mule was the nickname for a machine invented in 1779, that allowed the spinning of strong and fine yarn.
2. Water Frame, invented in 1769 by Richard Arkwright, made it possible to weave pure cotton clothes.
3. Power loom, invented by Edmund Cartwright in 1787, could be used to weave any kind of materials.

Select the correct answer using the code given below :

1 and 2 only

1, 2 and 3

2 and 3 only

3 only

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All three statements are correct. Statement 1 is correct: The Spinning Mule, invented by Samuel Crompton in 1779, combined features of earlier machines and was capable of spinning fine and strong yarn, nicknamed ‘mule’ because it was a hybrid. Statement 2 is correct: The Water Frame, invented by Richard Arkwright in 1769, produced stronger yarn suitable for warps, enabling the weaving of pure cotton cloth (before this, cotton textiles often used linen warps). Statement 3 is correct: The Power Loom, invented by Edmund Cartwright in 1787, mechanized the weaving process. While initial versions had limitations, the technology rapidly improved and was adapted to weave various materials, revolutionizing textile production across different fibers.

Key inventions like the Spinning Mule, Water Frame, and Power Loom significantly mechanized the textile industry during the Industrial Revolution, increasing productivity and changing manufacturing processes.

These inventions were crucial in shifting textile production from cottage industries to factories. The increased efficiency of spinning and weaving lowered the cost of textiles, making them more accessible. The demand for cotton grew, impacting agriculture (especially in the Americas) and trade networks.

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32. Consider the following statements : 1. Terracotta models of the plou

Consider the following statements :

1. Terracotta models of the plough have been found at sites in Cholistan and at Banawali (Haryana).
2. There is evidence of a ploughed field at Kalibangan associated with the mature phase of the Harappan civilization.
3. The ploughed field at Kalibangan had two sets of furrows crossing at right angles to each other suggesting two different crops were grown together in it.

Which of the statements given above are correct ?

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1, 2 and 3

2 and 3 only

1 and 3 only

None of the above

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Statements 1 and 3 are correct. Terracotta models of ploughs have been found at archaeological sites associated with the Harappan civilization, including Banawali in Haryana and sites in Cholistan (statement 1). There is clear archaeological evidence of a ploughed field at Kalibangan. While statement 2 mentions the ‘mature phase’, the ploughed field discovered at Kalibangan is primarily associated with the Early Harappan phase. Statement 3 accurately describes the ploughed field at Kalibangan, which shows two sets of furrows crossing at right angles, a pattern suggesting the practice of double cropping (growing two different crops simultaneously in the same field). Therefore, statements 1 and 3 are correct, and statement 2 is inaccurate regarding the phase.

Archaeological evidence from Harappan sites indicates knowledge of agriculture, including the use of ploughs (models found) and specific techniques like double cropping (evidence at Kalibangan). The ploughed field at Kalibangan is a significant find, demonstrating agricultural practices.

The ploughed field at Kalibangan is one of the earliest examples of a ploughed field discovered in the world. The crossing furrows at right angles are indicative of sowing seeds in both directions, a method likely aimed at maximizing land use and yield by growing two crops with different water requirements or growth cycles.

33. Which among the following statements with respect to carbon is/are cor

Which among the following statements with respect to carbon is/are correct ?

1. Carbon forms the basis for all living organisms and many things we use
2. Carbon shows tetra-valency and the property of catenation
3. Carbon forms covalent bonds with itself and other elements
4. Carbon forms compounds containing triple and tetra bonds between carbon atoms

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1 only

1 and 2 only

1, 2 and 3

2 and 4

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Statements 1, 2, and 3 are correct. Carbon forms the backbone of all organic life and is present in countless materials we use (statement 1). Carbon has four valence electrons, allowing it to form four covalent bonds (tetra-valency), and it can bond with itself to form long chains or rings (catenation) (statement 2). Carbon forms covalent bonds not only with itself but also with other elements like hydrogen, oxygen, nitrogen, etc. (statement 3). Statement 4 is incorrect; carbon forms single, double, and triple bonds with other carbon atoms but not stable tetra (quadruple) bonds in typical organic chemistry contexts.

Carbon’s unique properties of tetra-valency and catenation, and its ability to form strong covalent bonds, are fundamental to organic chemistry and the diversity of carbon compounds. Carbon forms single, double, and triple bonds, but not quadruple bonds, between carbon atoms in stable molecules.

The vast number of carbon compounds makes organic chemistry a distinct branch of chemistry. Catenation is particularly strong in carbon, enabling the formation of complex molecular structures. While theoretical studies have explored the possibility of quadruple bonds in some exotic carbon species, they are not characteristic of carbon bonds in everyday substances.

34. As proposed by Dalton, which of the following symbol represents phosph

As proposed by Dalton, which of the following symbol represents phosphorus ?

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Circle with P inside

Circle with L inside

Circle with vertical and horizontal lines crossing in the center

Circle with three lines radiating from the center to the circumference

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As proposed by Dalton in his atomic theory, each element had a unique symbol. Phosphorus was represented by a circle with three lines radiating outwards from the center to the circumference.

Dalton’s symbols were pictorial representations of elements and compounds, unlike the modern alphabetical symbols.

Other examples of Dalton’s symbols include a simple circle for Oxygen, a circle with a dot in the center for Hydrogen, and a circle with vertical and horizontal lines crossing for Sulphur (often shown as + inside circle or vertical/horizontal lines). Option A represents the modern symbol for Phosphorus inside a circle, which was not Dalton’s representation.

35. Kerosene and petrol mixture can be best separated by

Kerosene and petrol mixture can be best separated by

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Sublimation

Separating funnel

Fractional distillation

Compressing and cooling

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The correct method to separate a mixture of kerosene and petrol is fractional distillation. Both kerosene and petrol are miscible liquids with different boiling points (petrol boils roughly between 40°C and 205°C, kerosene between 175°C and 325°C). Fractional distillation is used to separate miscible liquids that have close boiling points.

Fractional distillation is a technique used to separate miscible liquids with different boiling points, involving repeated vaporization and condensation steps within a fractionating column.

Sublimation is used for separating a solid that sublimes from a non-subliming solid or a liquid. A separating funnel is used to separate immiscible liquids. Compressing and cooling is a method used to liquefy gases.

36. Which among the following is NOT true with respect to colloidal soluti

Which among the following is NOT true with respect to colloidal solution ?

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Particles are uniformly distributed throughout the solution

Colloidal solution is homogenous in nature

They show Tyndal effect

They do not settle down when kept undisturbed

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The statement “Colloidal solution is homogenous in nature” is NOT true.

Colloidal solutions are fundamentally heterogeneous mixtures. Although they may appear homogeneous to the naked eye because the dispersed particles do not settle out, they are heterogeneous at the microscopic level.

Properties of colloidal solutions include: they are heterogeneous; the particle size is larger than in true solutions but smaller than in suspensions (typically 1 nm to 1 $\mu$m); they exhibit the Tyndall effect (scattering of light); they undergo Brownian motion; they are generally stable and do not settle down when left undisturbed; they often carry an electric charge. Statement A is also generally not strictly true in the sense of uniform distribution like a true solution, but B is the most definitive and fundamental falsehood about the nature of colloids.

37. Which one of the following metals can be extracted using carbon as red

Which one of the following metals can be extracted using carbon as reducing agent ?

Zinc

Silver

Gold

Aluminum

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Zinc can be extracted using carbon as a reducing agent.

Metals less reactive than carbon can be extracted from their oxides by reduction with carbon (smelting). In the reactivity series, carbon is more reactive than zinc, silver, and gold, but less reactive than aluminium. Therefore, oxides of zinc, silver, and gold can potentially be reduced by carbon, while aluminium oxide cannot.

Aluminium is extracted by electrolysis of molten aluminium oxide (alumina) using the Hall-Héroult process because it is much more reactive than carbon. Zinc is commonly extracted from its oxide ($\text{ZnO}$) by heating it with carbon in a process called smelting: $\text{ZnO} + \text{C} \rightarrow \text{Zn} + \text{CO}$. Silver and gold are often found in native states or extracted using processes like cyanidation or from sulfide ores, although carbon can be involved in some extraction stages for silver, zinc is a clearer example of direct oxide reduction by carbon among the options.

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38. A block of wood (dimensions : $40 \text{ cm} \times 20 \text{ cm} \tim

A block of wood (dimensions : $40 \text{ cm} \times 20 \text{ cm} \times 10 \text{ cm}$) is kept on a tabletop in three different positions : (a) with its side of dimensions $20 \text{ cm} \times 10 \text{ cm}$; (b) with its side of dimensions $10 \text{ cm} \times 40 \text{ cm}$; and (c) with its side of dimensions $40 \text{ cm} \times 20 \text{ cm}$. The pressure exerted by the wooden block on the tabletop in these positions is represented by $P_A$, $P_B$ and $P_C$ respectively. The pressure follows the trend

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[amp_mcq option1=”$P_A > P_B > P_C$” option2=”$P_A < P_B < P_C$" option3="$P_A = P_B = P_C$" option4="$P_A < P_B = P_C$" correct="option1"]

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The pressure follows the trend $P_A > P_B > P_C$.

Pressure is defined as force per unit area ($P = F/A$). The force exerted by the wooden block on the tabletop is its weight, which is constant regardless of its orientation. Therefore, the pressure exerted is inversely proportional to the area of contact. The smallest contact area will exert the highest pressure, and the largest contact area will exert the lowest pressure.

The dimensions are 40 cm x 20 cm x 10 cm. The areas of contact in the three positions are:
(a) $A_A = 20 \text{ cm} \times 10 \text{ cm} = 200 \text{ cm}^2$
(b) $A_B = 10 \text{ cm} \times 40 \text{ cm} = 400 \text{ cm}^2$
(c) $A_C = 40 \text{ cm} \times 20 \text{ cm} = 800 \text{ cm}^2$
Comparing the areas: $A_A < A_B < A_C$. Since $P \propto 1/A$, the corresponding pressures will be $P_A > P_B > P_C$.

39. The motion of a particle of mass m is described by the relation, $y =

The motion of a particle of mass m is described by the relation, $y = ut – \frac{1}{2}gt^2$, where $u$ is the initial velocity of the particle. The force acting on the particle is

$F = mleft(rac{du}{dt} ight)$

$F = mg$

$F = mleft(rac{dy}{dt} ight)$

$F = -mg$

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The force acting on the particle is $F = -mg$.

The given equation of motion, $y = ut – \frac{1}{2}gt^2$, describes uniformly accelerated motion under gravity. By taking the second derivative of the displacement ($y$) with respect to time ($t$), we find the acceleration. The first derivative gives velocity: $\frac{dy}{dt} = u – gt$. The second derivative gives acceleration: $\frac{d^2y}{dt^2} = -g$. According to Newton’s second law, the force is given by $F = ma$. Since the acceleration is $a_y = -g$, the force is $F_y = m(-g) = -mg$. The negative sign indicates the force is acting in the negative y direction, which corresponds to the downward direction (gravity) if the initial upward direction was taken as positive y.

The equation $y = ut – \frac{1}{2}gt^2$ is the standard kinematic equation for vertical displacement under constant gravitational acceleration ($g$), with initial velocity $u$. The force responsible for this motion is the gravitational force, which is $mg$ acting downwards. Assuming the upward direction as positive y, the downward force is represented as $-mg$.

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40. What will happen if a collection of positive and negative charges are

What will happen if a collection of positive and negative charges are passed at a high speed through a magnetic field which is perpendicular to the direction of motion of the charges ? (Assume that both kind of charges are NOT going to recombine)

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Both kind of charges will stop moving

Positive charges and negative charges will separate out

Positive charges will stop but negative charges will continue moving uninterrupted

Both kind of charges will keep moving uninterrupted

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When a collection of positive and negative charges are passed at high speed through a magnetic field perpendicular to their motion, the positive and negative charges will separate out.

The Lorentz force ($\vec{F} = q(\vec{v} \times \vec{B})$) acts on a moving charge in a magnetic field. The force is perpendicular to both the velocity ($\vec{v}$) and the magnetic field ($\vec{B}$). For positive charges, the force direction is given by the right-hand rule applied to $\vec{v} \times \vec{B}$. For negative charges (where $q$ is negative), the force is in the opposite direction. This difference in the direction of the force causes the positive and negative charges to be deflected in opposite directions, leading to separation.

This principle is utilized in devices like mass spectrometers or velocity selectors to separate charged particles based on their mass-to-charge ratio or velocity. The charges will move in curved paths, not stop or continue uninterrupted, as long as they are within the magnetic field.