Science and Technology: UPSC Previous Year Questions (Prelims)

Explanation

Green hydrogen is expected to play a prominent role in decarbonising heavy industries, including oil refineries, steel mills and fertiliser plants. Green hydrogen is produced by breaking down water in an electrolyser using only renewable energy, resulting in no carbon emissions. The production of fertiliser demands substantial energy, typically sourced from fossil fuels like natural gas. However, green hydrogen offers a promising alternative, serving either as an electricity source or directly utilised in the ammonia production process, which is crucial for manufacturing fertilizer. Oil refineries significantly contribute to greenhouse gas emissions through their energy-intensive operations and dependence on fossil fuels. However, integrating green hydrogen into refinery operations offers a viable solution to mitigate this impact by either substituting or complementing fossil fuels, thereby decreasing their carbon footprint. Hydrogen can play a vital role in refining procedures like hydrocracking and hydrotreating, enhancing fuel quality by eliminating impurities. The steel industry contributes substantially to worldwide carbon emissions. However, the adoption of green hydrogen presents an opportunity to address this issue by serving as a replacement for coal or coke as a reducing agent in the steelmaking process. Green hydrogen enables the Direct Reduced Iron (DRI) process, producing environmental -friendly or low-carbon steel. It can also support heat and electricity generation, further cutting emissions.

Explanation

Statement 1 is correct: Finely ground basalt rock is dispersed across agricultural lands to expedite the natural absorption of carbon dioxide from the atmosphere. This is known as enhanced rock weathering, where silicate minerals react with CO₂, forming stable carbonates and reducing atmospheric carbon, as well as improving the fertility of the soil.

Statement 2 is correct: This method, referred to as ocean alkalinity enhancement, encompasses the addition of lime (calcium oxide or calcium hydroxide) to the oceans to elevate their alkalinity. By doing so, it boosts the oceans’ ability to absorb and retain carbon dioxide from the atmosphere, thus assisting in carbon sequestration.

Statement 3 is correct: The process known as carbon capture and storage (CCS) involves capturing carbon dioxide emissions from industrial processes and storing them underground. Abandoned subterranean mines can be utilised as viable storage sites, where the captured carbon dioxide is injected into these locations as carbonated waters.

Explanation

An accelerometer is an electromechanical device used to measure acceleration forces. These forces may be static like the continuous force of gravity or dynamic force to sense movement or vibrations.

Statement 1 is correct: Upon a collision, the crash sensor, typically an accelerometer, transmits a signal to the airbag control unit to deploy the airbags almost immediately.

Statement 2 is correct: Accelerometers in laptops protect hard drives from damage. If the laptop were to suddenly drop while in use, the accelerometer would detect the sudden free fall and immediately turn off the hard drive to avoid hitting the reading heads into the hard drive platter.

Statement 3 is correct: Accelerometer is used in smartphones as it detects the rotation of their display between portrait and landscape mode depending on the tilt of the phone.

Explanation

Statement 1 is correct: The use of biofilters to remove toxins from wastewater and waste gases has advanced in recent decades. In order to remove contaminants from a fluid stream, biofilters fix microorganisms to an inorganic/organic medium (carrier), which has the ability to break down a wide range of chemicals. By removing uneaten fish feed, they additionally perform waste treatment.

Statement 2 is correct: By constructing a biofilter correctly, it is possible to regulate ammonia and nitrite concentrations at levels safe for fish. Through the biofiltration process, ammonia nitrogen is converted into nitrite nitrogen, which is subsequently transformed into less harmful nitrate nitrogen, ensuring a conducive environment for fish.

Statement 3 is incorrect: Biofilters do not increase phosphorus as a nutrient for fish in water. Phosphorus (P) is actually removed by biofilters to prevent eutrophication in waters.

Explanation

Green hydrogen is a renewable energy source that, unlike coal and oil, solely releases water vapour and leaves no residue in the air.

Statement 1 is correct: Hydrogen, a zero-carbon fuel, can be used to power automobiles through both hydrogen internal combustion engines and hydrogen fuel cells.Hydrogen engines utilize hydrogen in an internal combustion engine, operating similarly to the way gasoline powers conventional engines.

Statement 2 is correct: Clean hydrogen may be created and injected into natural gas pipelines to create blends that can be utilised to provide heat and power with fewer emissions than just natural gas.

Statement 3 is correct: A fuel cell harnesses the chemical energy of green hydrogen or alternative fuels to generate electricity in a clean and efficient manner. When hydrogen serves as the fuel, the sole byproducts produced are electricity, water, and heat.

Explanation

Probiotics are live microorganisms that are intended to have health benefits when consumed or applied to the body.

Statement 1 is correct: Probiotics can be composed of bacteria, yeast, or both. The most common types of bacteria used as probiotics are Lactobacillus and Bifidobacterium, while Saccharomyces boulardii is an example of a yeast that is sometimes used as a probiotic.

Statement 2 is incorrect: Probiotics contain microorganisms that are similar to or the same as those naturally present in our bodies, especially in the digestive tract. Our gut microbiota consists of many types of bacteria, some of which are also found in probiotic products. These probiotics are often called "good" or "friendly" bacteria because they support gut health.

Statement 3 is correct: Some probiotic bacteria, like Lactobacillus, produce an enzyme called lactase, which helps in the digestion of milk sugar (lactose). Lactase breaks down lactose into simpler sugars, making it easier for the body to absorb. This is especially helpful for people who are lactose intolerant and have difficulty digesting dairy products.

Explanation

B cells and T cells are integral components of the human immune system, each playing distinct roles in protecting the body from diseases caused by pathogens. B cells are primarily responsible for humoral immunity. They produce antibodies that specifically target and neutralize pathogens such as bacteria and viruses. T cells play a crucial role in cell-mediated immunity, not by producing antibodies but by carrying out essential immune functions. Helper T cells activate B cells to stimulate other immune cells to enhance the body’s defense. Cytotoxic T cells target and destroy infected or cancerous cells, eliminating harmful threats. Regulatory T cells help maintain immune balance by preventing excessive or inappropriate immune responses.

Explanation

Software as a Service (SaaS) refers to software provided by a third party as a service where hosting and maintenance are managed by the provider. Unlike traditional methods requiring local deployment and maintenance SaaS allows direct access to software via thin clients such as web browsers.

Statement 1 is correct: SaaS applications often provide customization options, allowing users to adjust the user interface (UI) and modify data fields according to their business requirements. However, customization is typically limited to certain areas defined by the service provider and may not involve deep structural changes.

Statement 2 is correct: SaaS platforms are accessible via the internet and can be used across devices, including desktops, laptops, and mobile devices. This accessibility is a key feature of SaaS, as users can access their applications and data on the go through web browsers or mobile apps.

Statement 3 is correct: Email services such as Outlook, Hotmail, and Yahoo Mail are classic examples of SaaS. They deliver email functionality over the internet without requiring users to install software locally. These services are hosted by the provider and accessed through browsers or apps.

Explanation

Statement 1 is correct: A fundamental principle of Web 3.0 is to grant users ownership and control over their personal data, reducing reliance on centralized entities. This shift aims to enhance privacy and security for individuals.

Statement 2 is correct: Web 3.0 leverages blockchain technology to create decentralized applications, including social networks. These platforms operate without central authorities, offering users greater control over content and data.

Statement 3 is correct: Decentralization is a hallmark of Web 3.0, where control is distributed among users instead of being held by centralized corporations. This collective operation is facilitated through decentralized networks and consensus mechanisms.

Explanation

Quantum computers are machines that use the properties of quantum physics to store data and perform computations. A classical computer performs operations using classical bits, which can be either 0 or 1. Quantum computer uses quantum bits or Qubits, which can be both 0 and 1 at the same time. Qubits (or quantum bits) are the units of computation in quantum computers. They take advantage of quantum mechanics characteristics, which regulate how matter behaves at the atomic level. Quantum computers are faster, more accurate, & energy efficient. Two important phenomena of quantum physics that are used to achieve functioning of quantum computing are:

1. Superimposition: Each quantum bit (basic unit of information in a quantum computer) can represent both a 1 and a 0 at the same time, which is known as superposition.

2. Quantum Entanglement: Subatomic particles become "entangled" (connected) in quantum entanglement, which means that any change in one upsets the other, even though they are at opposite ends of the universe.