After analysing the Question Paper, it can be concluded that the examiner has tested the knowledge of the basic  and the current issues related to the scientific field.

There were 7 Questions from Science & Technology in 2024, of which

• 1 Question from Energy (RTG)
• 1 Question from Space (Stars)
• 1 Question from Biology (Blood Vessels)
• 1 Question from Physics (Radars)
• 1 Question from Defence (Fifth-generation Aircraft)
• 1 Question from Chemistry (Hydrogel)
• 1 Question from Computing (Metaverse)

The level of the questions was Moderate to Tough.

Most of the questions were aimed at testing the analytical abilities of the candidates.

Solved PYQs Science & Technology With Explanation 2024 UPSC Prelims (Previous Year Questions) 

1. With reference to radioisotope thermoelectric generators (RTGs), consider the following statements:

1. RTGs are miniature fission reactors.

2. RTGs are used for powering the onboard systems of spacecraft.

3. RTGs can use Plutonium-238, which is a by-product of weapons development.

Which of the statements given above are correct?

(a) 1 and 2 only

(b) 2 and 3 only

(c) 1 and 3 only

(d) 1, 2 and 3

1. Ans: b

Explanation:

Radioisotope Thermoelectric Generators (RTGs) are lightweight, compact spacecraft power systems. RTGs provide electrical power using heat from the natural radioactive decay of plutonium-238, in the form of plutonium oxide. 

Sometimesreferred to as “nuclear batteries,” RTGs are not fission reactors,  nor is plutonium the type that is used for nuclear weapons. 

Hence, statement 1 is incorrect & statement 2 is correct.

The fuel in an RPS — short for radioisotope power systems — is plutonium oxide, a radioactive material that produces alpha particles. Alpha particles are a particular type of ionizing radiation that can be shielded by material as thin as a piece of paper. 

Plutonium-238 is not the type of plutonium used for nuclear weapons and would not work well as fuel in a nuclear reactor.

In 1959, a prototype RTG generated a sustained 2.5 watts of power over 90 days rapid advances in nuclear chemistry — in the U.S., an outgrowth of the World War II-era Manhattan Project that produced the first nuclear weapons — yielded an array of new radioactive materials. One of these, Pu-238, is nearly ideal for fueling RTGs. 

Hence, statement 3 is correct.

2. Consider the following statements:

Statement I: Giant stars live much longer than dwarf stars.

Statement II: Compared to dwarf stars, giant stars have a greater rate of nuclear reactions.

Which one of the following is correct in respect of the above statements?

(a) Both Statement-I and Statement-II are correct and Statement-II explains Statement-I

(b) Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I

(c) Statement I is correct, but Statement II is incorrect

(d) Statement I is incorrect, but Statement II is correct

2. Ans: d

Explanation:

There are two kinds of very large stars. Giant stars have masses from eight times to as much as 100 times that of the mass of our sun. These massive stars have hotter and denser cores than dwarf stars (stars that are smaller than five times the mass of our sun). Therefore, giant stars have a greater rate of the nuclear reactions that light up stars. Massive stars also use up the hydrogen fuel in their core faster, despite starting out with much more of it, meaning they live much shorter lives than dwarf stars.

Dwarf stars will shine for trillions of years while some Giant stars will live for only a few million years.

Hence, statement 1 is incorrect & statement 2 is correct.

3. Which one of the following is synthesised in the human body that dilates blood vessels and increases blood flow?

(a) Nitric oxide

(b) Nitrous oxide

(c) Nitrogen dioxide

(d) Nitrogen pentoxide

3. Ans: a

Explanation: 

Vasodilation refers to a widening of the blood vessels within the body. This occurs when the smooth muscles in the arteries and major veins relax.

Vasodilation occurs naturally in response to low oxygen levels or increases in body temperature. Its purpose is to increase blood flow and oxygen delivery to parts of the body that need it most.

The release of certain chemicals within the body can cause vasodilation. Examples include nitric oxide and carbon dioxide, as well as hormones such as histamine, acetylcholine, and prostaglandins.

A doctor may sometimes induce vasodilation as a treatment for high blood pressure, also known as hypertension, and its related conditions

Hence, option a is correct. 

4. Consider the following activities:

1. Identification of narcotics on passengers at airports or in aircraft

2. Monitoring of precipitation

3. Tracking the migration of animals

In how many of the above activities can the radars be used?

(a) Only one

(b) Only two

(c) All three

(d) None

4. Ans: b

Explanation:

RADAR is an electromagnetic system for the detection and location of target objects such as aircraft, ships, spacecraft, vehicles, people, and the natural environment which can reflect a signal back. It uses electromagnetic radio waves to determine the angle, range, or velocity of objects.

A weather radar can determine the precipitation type (rain, snow, hail, etc.) and spot its location. With the help of a weather radar map, it is also possible to predict where the rain will be moving next and how intense it will be. 

Radar has several benefits over other techniques to study migration such as visual observations, trapping, and banding, as it works well at altitude and over large distances, is unaffected by the absence of light, and is relatively independent of weather conditions.

Hence 2 and 3 are correct with respect to RADARS

Radars are not used  for detection of Narcotics rather other techniques like 

Trace narcotic detectors offer a vital tool for identifying microscopic chemical signatures from drugs and residues. Tiny samples are analyzed to reveal narcotic evidence even when no drugs are visible.

Trace detectors collect minute samples via methods like air puffs or swabs wiped over surfaces and materials. Advanced instrumentation analyzes each sample for the presence of chemical markers associated with narcotics. Trace residues of drugs, manufacturing chemicals, or cutting agents can be identified even at levels invisible to the naked eye.

Ion Mobility Spectrometry (IMS) and Mass Spectrometry provide rapid yet highly precise identification of narcotic signatures.  IMS analyzes the mobility rate of ionized molecules in an electric field, while mass specrometry separates compounds by their mass-to-charge ratio.

Both methods can detect drug traces down to pictograms or nanograms. This enables the discovery of clandestine threats that evade standard security screening.

Full-body X-ray scanners:-  X-ray scanners can be an effective tool for detecting narcotics and other hazardous items. Leveraging state-of-the-art neural network algorithms and knowledge of human body physiology, the software visualizes suspicious areas with an indication of the probability of drug and narcotic presence. In a matter of seconds, it analyzes images and outlines potential areas where narcotics and drugs may be concealed.

Hence, option b is correct.

5. Consider the following aircraft:

1. Rafael

2. MiG-29

3. Tejas MK-1

How many of the above are considered fifth-generation fighter aircraft?

(a) Only one

(b) Only two

(c) All three

(d) None

5. Ans: d

Explanation:

Fifth-generation fighter aircraft are the most technologically advanced jets ever built. They were designed to operate with the help of digital programs and fly by wire to counter the threats they faced on the battlefield. Sophisticated avionics, stealth technology, and super manoeuvrability are just a few advantages over older jets that give them domination in the sky.

few countries have decided to pursue the development of fifth-generation fighter jets:

• Lockheed F-22 Raptor and F-35 Lighting II – USA
• Sukhoi T-50 PAK-FA – Russia
• Chengdu J-20 and Shenyang J-31 Gyrfalcon – China 

Hence, option d is correct.

6. In which of the following are hydrogels used?

1. Controlled drug delivery in patients

2. Mobile air-conditioning systems

3. Preparation of industrial lubricants 

Select the correct answer using the code given below:

(a) 1 only

(b) 1 and 2 only

(c) 2 and 3 only

(d) 1, 2 and 3

6. Ans: a

Explanation:  

Hydrogel products constitute three-dimensional networks that contain a group of polymeric materials, the hydrophilic structure of which renders them capable of holding large amounts of water. These biomaterials can integrate large quantums of biological fluids and swell. When swelled, they are soft & rubbery and resemble the living tissue, exhibiting excellent biocompatibility. 

Hydrogels are smart enough to respond to fluctuations in environmental stimuli (ionic strength, pH, temp, presence of enzyme, electric field, etc.) 

Applications of  Hydrogel

Important advantages of hydrogels 

• They show high absorption capacity,,
• They maintain the pH value neutral after swelling into water,
• They have the least soluble content and the least residual monome,
• They achieve the desired rate of absorption related to the needs of the application,
• They have high durability and stability during storage,
• They have high biodegradability,
• They are colorless, odorless, and non-toxic,
• They have high photostability.

Application of hydrogels

• Drug delivery systems 
• Dyes and heavy metal ions removal in waste water
• contact lenses,
• Scaffolds in tissue engineering
• Biosensors
• Injectable hydrogel for spinal cord regeneration
• Supercapacitor hydrogels
• Impact protectors (cushioning)  

Mobile Air Conditioning (MAC) system

Mobile Air Conditioning (MAC) system, is commonly known as car AC or vehicle AC system. 

The air conditioning system in a car works by manipulating refrigerant between a liquid and a gaseous state. As the refrigerant changes states, it absorbs heat and humidity from the vehicle and allows the system to give off cool, dry air.

The refrigerant used in automotive air conditioning systems has changed from R-12 (Freon) to R-134a and now to R-1234yf, which produces fewer greenhouse gases.

Almost 100% of new passenger cars sold in the EU use HFO-1234yf as refrigerant. 

Hydrogels have no relevance in Car air conditioning systems 

MIT engineers have now found that polyethylene glycol (PEG) — a hydrogel commonly used in cosmetic creams, industrial coatings, and pharmaceutical capsules — can absorb moisture from the atmosphere even as temperatures climb. It could be used for passive cooling or water harvesting in warm climates.

Hydrogels cannot be used for active cooling 

Industrial lubricants 

There are several types of industrial lubricants, including mineral oils, synthetic oils, greases, solid lubricants, and specialty lubricants. Each type has its own unique properties and applications

They are employed to reduce friction, prevent wear, dissipate heat, and protect against corrosion in moving parts.

Grease

Grease is a semisolid lubricant that consists of a base oil thickened with a soap-like material called a thickener. It offers excellent adhesion, sealing properties, and resistance to water washout. Grease is commonly used in applications with slow or intermittent movement, high loads, and extreme temperatures. 

Liquid Lubricants

Liquid lubricants, commonly referred to as oils, are fluid lubricants that offer excellent lubrication properties. They are used in applications where continuous lubrication is required, such as circulating systems or machinery with complex parts. 

Liquid lubricants are available in various formulations, including mineral oils, synthetic oils, and vegetable-based oils. 

Mineral oils are derived from crude oil (Fractional distillation))and are cost-effective, while synthetic oils are chemically engineered to offer superior performance, such as high-temperature stability and extended oil change intervals.

 Vegetable-based oils are environmentally friendly options that are biodegradable and less toxic. 

The Effects of Water on a Lubricant

Not only does water have a direct harmful effect on machine components, but it also plays a direct role in the ageing rate of lubricating oils.  

Hydrogel has no relevance in Lubricant production

Hence, option a is correct.

7. Which one of the following words/phrases is, most appropriately used to denote “an interoperable network of 3D virtual worlds that can be accessed simultaneously by millions of users, who can exert property rights over virtual items”?

(a) Big data analytics

(b) Cryptography

(c) Metaverse

(d) Virtual matrix

7. Ans: c

Explanation:

The metaverse implies a shared environment that spans a multitude of 3D virtual worlds. Participants in the metaverse will be able to move freely through these virtual worlds, taking their identities, entitlements and goods with them. At least that’s one vision of how a universe of 3D virtual worlds will work.  

Hence, option c is correct.