Miscellaneous: UPSC Previous Year Questions (Science and Technology)

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

The Fractional Orbital Bombardment System (FOBS) is a missile technology designed to place a nuclear warhead into a partial Earth orbit before deorbiting to strike a target. Unlike intercontinental ballistic missiles (ICBMs), FOBS takes an unpredictable orbital path, bypassing traditional radar systems and potentially striking from unexpected directions, such as via the South Pole. Originally developed by the Soviet Union in the 1960s, FOBS was tested with the R-36ORB missile but later abandoned under arms control treaties like SALT II and the Outer Space Treaty. Recent reports indicate renewed interest, with countries like China reportedly testing FOBS integrated with hypersonic glide vehicles. Its capability to evade missile defenses has raised global security concerns and spurred advancements in countermeasures. ICBM Radar Beam Launch site FOBS FOBS Apogee ~150 km ~1200 km Target Early-warning Radar Fig: Fractional Orbital Bombardment System (FOBS)

Explanation

A biofilm is a collection of microbial cells that are encased in a polysaccharide-based matrix and are permanently attached to a surface (i.e., cannot be removed by gentle rinsing). Microorganisms that form biofilms include bacteria, fungi, and protists. Noncellular materials such as mineral crystals, corrosion particles, clay or silt particles, or blood components, depending on the environment in which the biofilm has developed, may also be found in the biofilm matrix.

Statement 1 is correct: Biofilms may form on a wide variety of surfaces, including living tissues, food and food processing surfaces, indwelling medical devices (devices in the body like catheters, heart valves), human and animal tissue, industrial or potable water system piping, or natural aquatic systems.

Statement 2 is correct: Biofilms are a significant concern in the food industry, forming on surfaces such as cutting boards, conveyor belts, and food packaging equipment. Contaminated biofilms can lead to foodborne illnesses caused by pathogens like Listeria monocytogenes, Salmonella, and Escherichia coli.

Statement 3 is correct: Microorganisms in biofilms are significantly more resistant to antibiotics compared to planktonic (free-floating) cells because:

The EPS (extracellular polymeric substance) matrix acts as a barrier, limiting antibiotic penetration. Cells within biofilms have reduced metabolic activity, making them less susceptible to antibiotics targeting active processes. Some bacteria within biofilms can exchange antibiotic resistance genes via horizontal gene transfer. This resistance complicates treatment, especially in chronic infections such as cystic fibrosis, where Pseudomonas aeruginosa biofilms are common.

Explanation

A pressure cooker is a sealed chamber that traps the steam generated as its contents are heated. As steam builds, pressure increases, driving the boiling point of water past 212°F (100°C). In general, this higher temperature shortens cooking times and, due to a lack of evaporation, extracts flavor more efficiently from foods.

Statement 1 is correct: The area of the hole directly influences the pressure and temperature inside the cooker. The hole in the lid is where steam escapes through the pressure regulator (weight valve). A smaller hole allows less steam to escape, which increases the pressure inside, raising the boiling point of water and increasing the cooking temperature. If the hole is larger, more steam escapes, reducing the pressure and lowering the cooking temperature.

Statement 2 is incorrect: A higher flame heats the pressure cooker faster but it does not increase the maximum cooking temperature once the cooker reaches its operating pressure. The pressure and temperature inside the cooker are controlled by the pressure regulator (weight valve), not the external flame. Once the required pressure is reached, excess heat only results in more steam escaping through the valve rather than increasing the cooking temperature.

Statement 3 is correct: The weight of the lid (specifically, the weight valve) is a key factor in determining the cooking temperature. The weight of the pressure regulator (weight valve) on the lid determines the maximum pressure inside the cooker. A heavier weight means the steam must build up more pressure before it can escape, increasing the boiling point of water and the cooking temperature. If the weight is lighter, steam escapes more easily, resulting in lower pressure and temperature inside the cooker.

Explanation

The artificial culture media, also referred to as the growth medium, is a setting for the development of many kinds of microorganisms. The agarose and nutrients needed for the microorganism’s growth are present in the culture medium. This medium is first sterilised to prevent contamination, which prevents the growth of undesirable microorganisms and ensures that it only contains the microbes of interest.

Option 1 is correct: Bacteria can be easily grown on artificial or synthetic media as these provide the necessary nutrients for their growth. These media typically include essential components like carbon, nitrogen, vitamins, and minerals. For instance, nutrient agar and broth are commonly used for culturing bacteria, and Escherichia coli can be grown on Luria-Bertani (LB) agar.

Option 2 is correct: Fungi, including yeasts and molds, can thrive on artificial media specifically formulated for their growth. Media such as Sabouraud dextrose agar and potato dextrose agar are designed to support fungal growth by providing nutrients and maintaining an acidic pH, which inhibits bacterial contamination.

Option 3 is incorrect: Viruses differ significantly from bacteria and fungi because they cannot replicate independently. Being obligate intracellular parasites they require living host cells to reproduce. Thus, they are cultured by infecting host systems such as bacterial cells (for bacteriophages) or eukaryotic cells (for animal viruses) and cannot grow on synthetic media alone.

Explanation

Statement 1 is correct: Sodium Lamps emit light omnidirectionally (360 degrees), necessitating the use of reflectors to direct light toward the desired area. LED Lamps emit light directionally (typically around 180 degrees), allowing for more efficient illumination with minimal light loss.

Statement 2 is incorrect: Sodium Lamps have a shorter operational lifespan compared to LEDs. LED Lamps offer a longer lifespan, often exceeding that of sodium lamps, leading to reduced maintenance and replacement costs.

Statement 3 is correct: Sodium Lamps produce a nearly monochromatic light, resulting in poor color rendering and making it difficult to distinguish colors under their illumination. LED Lamps provide a broad spectrum of visible light, offering superior color rendering and enhancing visibility and safety in street lighting applications.

Explanation

Bisphenol A (BPA) is an industrial chemical primarily used in the production of polycarbonate plastics and epoxy resins. Polycarbonate plastics are known for their durability and clarity and are commonly utilized in items such as water bottles, food storage containers, and eyewear. It has been identified as an endocrine disruptor, meaning it can interfere with the body’s hormonal systems. Research has linked BPA exposure to various health issues, including reproductive disorders, metabolic disease, and developmental problems in children. Due to these concerns, many regulatory agencies have evaluated the safety of BPA in consumer products.

Explanation

Triclosan is an ingredient added to many consumer products intended to reduce or prevent bacterial contamination. It is added to some antibacterial soaps and body washes, toiletries, toothpastes, and some cosmetics. Some short-term animal studies have shown that exposure to high doses of triclosan is associated with a decrease in the levels of some thyroid hormones. Other studies have raised the possibility that exposure to triclosan contributes to making bacteria resistant to antibiotics.

Explanation

Water is often referred to as the "universal solvent" because it can dissolve more substances than any other liquid. This exceptional ability is primarily due to its dipolar nature. A water molecule has a bent shape, with the oxygen atom carrying a partial negative charge and the hydrogen atoms carrying partial positive charges. This polarity allows water molecules to surround and interact with various solutes, effectively breaking them apart and dissolving them. Water can develop a strong attraction to another substance, such as salt (NaCl) to the point where it can interfere with the attractive forces holding the sodium and chloride in the salt complex together and dissolve it. In organic chemistry, a dipolar compound or simply dipole is an electrically neutral molecule carrying a positive and a negative charge in at least one canonical description.

Explanation

A drone, technologically, is an unmanned aircraft.

They are formally known as unmanned aerial vehicles (UAVs). A drone is essentially a flying robot that can be remotely piloted or can fly on its own using software-controlled flight plans in embedded systems in conjunction with onboard sensors and GPS.

Statement 1 is correct: Modern agriculture has increasingly adopted drones for the application of pesticides and fertilizers. These drones offer precision in spraying, ensuring uniform coverage and reducing the exposure of farmers to harmful chemicals. For instance, a study published in Springer highlights that drones equipped with advanced sensors and high-resolution cameras can distinguish between healthy and infested crops, allowing for targeted pesticide application.

Statement 2 is correct: Drones equipped with visual and thermal cameras are utilized in geological studies to inspect active volcano craters. They can safely approach hazardous areas, capturing high-resolution images and collecting gas samples. Researchers from the German Research Centre for Geosciences (GFZ) successfully employed drones to study the active Santa Maria volcano in Guatemala.

Statement 3 is correct: Marine biologists have innovated methods to collect biological samples from whales using drones. By flying drones through the spouts of whales, researchers can gather respiratory droplets containing DNA, hormones, and microorganisms without disturbing the animals. This technique was employed in the Ocean Alliance’s SnotBot program.