Physics

161. Vehicles carrying inflammable materials usually have metallic ropes to

Vehicles carrying inflammable materials usually have metallic ropes touching the ground during motion in order to

[amp_mcq option1=”control the speed of the vehicle” option2=”conduct the charge produced by friction” option3=”conduct the current produced by inflammable material” option4=”provide earthing for lightning” correct=”option2″]

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The correct option is B) conduct the charge produced by friction.
Vehicles carrying inflammable materials can build up static electric charge due to the friction between the vehicle’s tyres and the road, the movement of the liquid/gas within the tank, or friction with air. This static charge can accumulate on the vehicle body. The metallic rope touching the ground provides a path for this charge to be safely conducted away into the earth, preventing the build-up of static electricity and eliminating the risk of a spark that could ignite the inflammable material.
Static electricity is a significant hazard when transporting inflammable substances. Dissipating the charge through earthing (grounding) prevents electrostatic discharge sparks, which could cause a fire or explosion. The metallic rope serves as a conductor connected to the vehicle chassis, ensuring continuous contact with the ground during motion.

162. ‘Hydraulic brakes’ and ‘Hydraulic lift’ are devices in which fluids ar

‘Hydraulic brakes’ and ‘Hydraulic lift’ are devices in which fluids are used for transmitting

[amp_mcq option1=”force” option2=”momentum” option3=”pressure” option4=”power” correct=”option3″]

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‘Hydraulic brakes’ and ‘Hydraulic lift’ are devices in which fluids are used for transmitting pressure.
These devices operate based on Pascal’s Principle, which states that pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and the walls of the containing vessel. In hydraulic systems, a small force applied to a small area (piston) creates pressure in the fluid (Pressure = Force/Area). This pressure is transmitted through the fluid to a larger area (piston), resulting in a larger force output (Force = Pressure * Area). The fluid acts as the medium to transmit this pressure.
While force is transmitted and amplified in hydraulic systems, the fundamental principle at play, enabling the transmission and multiplication of force, is the uniform transmission of pressure throughout the fluid. Work done (Force x Distance) is ideally the same at both input and output ends, neglecting energy losses, but the force and distance are traded off (small input force over large distance results in large output force over small distance).

163. The acceleration due to gravity on the surface of the Earth is maximum

The acceleration due to gravity on the surface of the Earth is maximum and it

[amp_mcq option1=”increases as we go up” option2=”decreases as we go up or down” option3=”increases as we go down” option4=”neither increases nor decreases as we go up or down” correct=”option2″]

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The acceleration due to gravity on the surface of the Earth is maximum, and it decreases as we go up or down.
The acceleration due to gravity (g) at a distance r from the center of the Earth (mass M) is given by g = GM/r². On the surface, r is the Earth’s radius (R), so g_surface = GM/R². As we go up, r increases (r = R + altitude), so g decreases according to the inverse square law. As we go down into the Earth, the mass (M) pulling us decreases (only the mass within the sphere of radius r contributes to the gravitational force at radius r, assuming uniform density for simplicity, though density varies in reality), while the distance from the center (r) decreases. The effect of decreasing mass outweighs the effect of decreasing distance, causing gravity to decrease linearly towards the center (g = GM_r/r², where M_r is the mass within radius r). Gravity is zero at the Earth’s center.
Therefore, gravity is maximum at the surface and decreases both above and below the surface. Minor variations exist due to altitude, latitude (Earth’s bulge), and local geological variations, but the general trend is decrease away from the surface.

164. Transformers are used in between the electric power stations and homes

Transformers are used in between the electric power stations and homes or factories in order to

[amp_mcq option1=”minimize the power loss in transmission cables” option2=”minimize the voltage drop in transmission cables” option3=”minimize the current drop in the transmission cables” option4=”provide constant voltage at the user end” correct=”option1″]

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Transformers are used in between the electric power stations and homes or factories in order to minimize the power loss in transmission cables.
Electric power is transmitted over long distances through cables. These cables have resistance, and power is lost as heat according to the formula P_loss = I² * R, where I is the current and R is the resistance of the cable. To minimize this power loss for a given amount of power being transmitted (P = V * I), the voltage (V) is stepped up to a very high level by transformers at the power station. This high voltage means the current (I) required to transmit the same power is much lower (I = P/V). A lower current significantly reduces the power loss (I²R) in the transmission lines. At the receiving end, transformers step the voltage back down for safe use in homes and factories.
While stepping up voltage does also reduce voltage drop (V_drop = I*R), the primary purpose of high-voltage transmission is the dramatic reduction in power loss, making long-distance transmission economically feasible. Transformers are essential for changing voltage levels efficiently in AC circuits.

165. At the time of short-circuit the current in the circuit,

At the time of short-circuit the current in the circuit,

[amp_mcq option1=”reduces substantially” option2=”does not change” option3=”increases heavily” option4=”varies continuously” correct=”option3″]

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At the time of short-circuit, the current in the circuit increases heavily.
A short circuit occurs when a low-resistance path is established between points in a circuit that are normally at different electrical potentials. According to Ohm’s Law (V = IR, or I = V/R), if the resistance (R) in a circuit decreases significantly while the voltage (V) remains relatively constant, the current (I) must increase dramatically.
This heavy increase in current during a short circuit can cause overheating, damage to wiring and components, and is a common cause of electrical fires. Protective devices like fuses and circuit breakers are designed to detect this surge in current and interrupt the circuit to prevent damage.

166. The first large research reactor of India that uses U-233 as fuel is

The first large research reactor of India that uses U-233 as fuel is

[amp_mcq option1=”ZERLINA” option2=”PURNIMA” option3=”DHRUVA” option4=”KAMINI” correct=”option4″]

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KAMINI (Kalpakkam Mini Reactor) is a research reactor located at the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam. It is the first reactor in the world that uses Uranium-233 (U-233) as fuel. While its power output is low (30 kWt), making the term “large” somewhat inaccurate compared to reactors like DHRUVA (100 MWt), it is an operational research reactor specifically designed to study U-233 fuel, which is key to India’s thorium fuel cycle program. ZERLINA and PURNIMA-II also used U-233 but were zero or very low power experimental assemblies used for specific lattice studies rather than continuous research operation. DHRUVA is India’s largest research reactor but uses natural uranium.
KAMINI is the only operational reactor in India listed that uses U-233 fuel. It is specifically designed for research purposes related to the thorium fuel cycle.
India has pursued a three-stage nuclear power program aimed at utilizing its vast thorium reserves. The thorium cycle involves breeding U-233 from thorium. KAMINI plays a role in studying the characteristics of U-233 fuel. It achieved criticality in 1996.

167. Steam at 100°C is more effective in heating than water at the same tem

Steam at 100°C is more effective in heating than water at the same temperature because

[amp_mcq option1=”steam is in the gaseous state and water is in the liquid state” option2=”steam has an additional heat known as ‘latent heat of vaporization'” option3=”water has hydrogen bonds but steam does not” option4=”transfer of heat from steam is easier than water” correct=”option2″]

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The correct option is B. Steam at 100°C is more effective in heating than water at 100°C because steam possesses additional energy in the form of latent heat of vaporization. This is the energy absorbed by water to change its state from liquid to gas at its boiling point (100°C) without a change in temperature. When steam comes into contact with a cooler surface, it condenses back into water at 100°C, releasing this large amount of latent heat, which is then transferred to the surface being heated. Water at 100°C does not have this stored latent heat to release upon changing state.
The question asks why steam at the same temperature as water is a more efficient heating medium. The key concept is latent heat.
The latent heat of vaporization of water at 100°C is approximately 2260 kJ/kg (or 540 cal/g). This means that condensing 1 kg of steam at 100°C to water at 100°C releases 2260 kJ of heat, which is significantly more than the heat released by simply cooling 1 kg of water from 100°C. This large amount of heat released upon condensation makes steam very effective for heating applications like steam engines, industrial processes, and steam burns.

168. X is twice as massive as Y. X also runs twice faster than Y. Which one

X is twice as massive as Y. X also runs twice faster than Y. Which one among the following is the ratio of kinetic energy of X and Y ?

[amp_mcq option1=”1 : 8″ option2=”8 : 1″ option3=”4 : 1″ option4=”2 : 1″ correct=”option2″]

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The ratio of kinetic energy of X and Y is 8 : 1.
The kinetic energy (KE) of an object is given by the formula KE = ½ * m * v², where m is the mass and v is the velocity. Given that the mass of X (m_X) is twice the mass of Y (m_Y), so m_X = 2 * m_Y. Also, the velocity of X (v_X) is twice the velocity of Y (v_Y), so v_X = 2 * v_Y.
KE_X = ½ * m_X * v_X² = ½ * (2 * m_Y) * (2 * v_Y)² = ½ * 2 * m_Y * 4 * v_Y² = 8 * (½ * m_Y * v_Y²)
KE_Y = ½ * m_Y * v_Y²
The ratio KE_X / KE_Y = [8 * (½ * m_Y * v_Y²)] / [½ * m_Y * v_Y²] = 8 / 1. Thus, the ratio is 8:1.
Kinetic energy is a scalar quantity representing the energy of motion. It is directly proportional to the mass of the object and the square of its velocity. Doubling the velocity has a much greater impact on kinetic energy than doubling the mass.

169. Which among the following is/are the reasons behind using Mercury in t

Which among the following is/are the reasons behind using Mercury in thermometers ?

  • 1. Mercury does not wet the inner sides of the thermometer.
  • 2. It can be seen easily in a thin capillary tube of the thermometer.
  • 3. It is a good conductor of heat.
  • 4. It is non-toxic.

Select the correct answer using the code given below :

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

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The reasons behind using Mercury in thermometers among the given options are that Mercury does not wet the inner sides of the thermometer, it can be seen easily in a thin capillary tube, and it is a good conductor of heat.
Mercury possesses several properties suitable for use in thermometers: 1) It has high surface tension and does not wet (stick to) the glass tube, allowing for accurate readings of the meniscus. 2) It is opaque and reflective, making the column easily visible against the glass. 3) It is a good conductor of heat, which facilitates faster transfer of heat from the object being measured to the mercury, allowing it to quickly reach thermal equilibrium. 4) Mercury is highly toxic, which is a disadvantage, not a reason for its use.
Other properties of mercury that make it suitable for thermometers include a relatively low freezing point (-38.83 °C) and a high boiling point (356.73 °C), giving it a wide range of use, and a uniform coefficient of thermal expansion within its liquid range. However, due to its toxicity, mercury thermometers are being increasingly replaced by alcohol-based or digital thermometers.

170. Gases may be distinguished from other forms of matter by their :

Gases may be distinguished from other forms of matter by their :

[amp_mcq option1=”lack of colour.” option2=”ability to flow.” option3=”inability to form free surfaces.” option4=”ability to exert a buoyant force.” correct=”option3″]

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Gases may be distinguished from other forms of matter by their inability to form free surfaces.
– Solids have fixed shape and volume. Liquids have fixed volume but take the shape of the container from the bottom up, forming a free surface under gravity. Gases take the shape and volume of the entire container.
– Gases expand to fill whatever container they are in, meaning they do not form a distinct boundary or “free surface” in the way liquids do.
– Lack of colour (A) is not universal for gases (e.g., NO2 is brown).
– Ability to flow (B) is characteristic of both liquids and gases (they are both fluids).
– Ability to exert a buoyant force (D) is also characteristic of both liquids and gases (both are fluids).
The defining characteristics of gases at a macroscopic level include: they have no fixed shape or volume, they are easily compressible, and they diffuse readily. The inability to form a free surface is a direct consequence of their molecules having high kinetic energy and weak intermolecular forces, causing them to spread out and occupy the entire volume of the container.
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