67th BPSC Prelims Re-exam 2022
General Science Previous Year Questions (PYQs)

Detailed Explanation:

The Thomson effect describes the generation of electromotive force (EMF) in a single conductor due to a temperature gradient along its length.

• Core Distinction: Unlike the Seebeck effect (requiring two dissimilar metals), Thomson effect occurs in a single homogeneous conductor with varying temperature.
• Mechanism: Electrons diffuse from hot to cold regions, creating a potential difference proportional to the temperature gradient.
• Therefore, potential variation due to temperature variation in a single conductor is the Thomson effect, making Option 4 the correct answer.

Detailed Explanation:

The Theory of Relativity was formulated by Albert Einstein in two parts: Special Relativity (1905) and General Relativity (1915).

• Special Relativity: Established that the speed of light is constant and the laws of physics are the same for all non-accelerating observers.
• General Relativity: Described gravity as the curvature of spacetime caused by mass and energy, replacing Newtonian gravity.
• Therefore, Albert Einstein is the scientist who presented the theory of relativity, making Option 4 the correct answer.

Detailed Explanation:

Avogadro's law states that under the same temperature and pressure, equal volumes of all gases contain equal number of molecules.

• Core Principle: Discovered by Amedeo Avogadro (1812), this fundamental gas law directly matches the question's description.
• Therefore, Avogadro's law is the correct answer, making Option 3 correct.

Detailed Explanation:

Galileo Galilei was the first to define speed quantitatively as distance covered per unit of time.

• Historical Context: Galileo introduced the concept during his studies on motion and kinematics in the early 17th century.
• Significance: He established speed as a measurable scalar quantity, laying the foundation for classical mechanics.
• Therefore, Galileo is credited with the first definition of speed, making Option 4 the correct answer.

Detailed Explanation:

Earth's rotation creates a centrifugal effect that opposes gravity, reducing the effective weight of objects, especially at the equator where the rotational radius is maximum.

• Apparent gravity formula: g' = g - ω²R, where ω is angular speed and R is Earth's radius at the equator.
• Increased spinning speed: Higher ω increases ω²R, thereby decreasing g' (apparent gravity).
• Weight reduction: Since weight = mg', a smaller g' directly reduces the body's weight at the equator.
• Therefore, faster Earth rotation decreases equatorial weight, making Option 1 the correct answer.

Detailed Explanation:

A vector quantity possesses both magnitude and direction, whereas a scalar quantity has only magnitude.

• Speed is a Scalar: It measures only how fast an object moves, without any directional information (e.g., 50 km/h).
• Velocity, Displacement, and Torque are Vectors: Velocity is speed with direction; displacement is change in position with direction; torque is rotational force with directional sense.
• Therefore, speed is the only scalar among the options, making Option 4 the correct answer.

Detailed Explanation:

The speed of light in a medium is inversely proportional to its refractive index.

• Refractive Index Values: Vacuum = 1.0, Air ≈ 1.0003, Water ≈ 1.33, Glass ≈ 1.5–1.65.
• Glass has the highest refractive index among the given options, resulting in the slowest speed of light.
• Therefore, light travels slowest through glass, making Option 3 the correct answer.

Detailed Explanation:

A washing machine uses centrifugal force during the spin cycle to separate water from clothes based on density differences.

• Centrifugation Principle: High-speed drum rotation creates outward force, pushing water through perforations while retaining heavier clothes inside.
• Therefore, the washing machine operates on centrifugation, making Option 2 the correct answer.

Detailed Explanation:

Edward Jenner performed the first successful vaccination in 1796 using cowpox material to immunize against smallpox, earning him the title Father of Immunology. Robert Koch discovered TB and cholera bacteria; Elie Metchnikoff pioneered immunity research; Joseph Lister introduced antiseptic surgery—none attempted the first vaccination. Therefore, Option 3 is the correct answer.

Detailed Explanation:

Enzymes are biological catalysts that accelerate chemical reactions in living organisms, and the vast majority are proteins. They possess specific three-dimensional structures formed by amino acid chains, enabling them to bind substrates and facilitate reactions.

While a few enzymes are ribozymes (RNA-based), over 99% of all known enzymes are proteinaceous. Lipids, acids, and alkalis serve other biological functions but do not constitute enzyme structure.

Therefore, proteins form the structural basis of most enzymes, making Option 4 the correct answer.

Detailed Explanation:

Carbohydrates are broken down during digestion into their simplest absorbable form, glucose, which is a monosaccharide. All complex carbohydrates (polysaccharides like starch) and disaccharides (like maltose, sucrose) are ultimately degraded to glucose for cellular absorption and energy production.

Glycerol is derived from lipid metabolism, maltose is a disaccharide that further splits into two glucose molecules, and amino acids are the end products of protein digestion.

Therefore, glucose is the ultimate degradation product of carbohydrates, making Option 2 the correct answer.

Detailed Explanation:

Earthworms lack red blood cells (RBCs); their respiratory pigment hemoglobin is dissolved directly in the plasma, not packed inside cells.

Snakes and peacocks are vertebrates that possess RBCs containing hemoglobin for oxygen transport.

Therefore, only earthworm is without red blood cells, making Option 1 the correct answer.

Detailed Explanation:

Chloroquine is an antimalarial drug used for treatment and prophylaxis of malaria, making this pair correctly matched.

Tuberculosis is prevented by BCG vaccine (not ATS); Tetanus is prevented by tetanus toxoid (not BCG); Scurvy results from vitamin C deficiency (not thiamine/vitamin B1).

Therefore, only Malaria-Chloroquine is correctly matched, making Option 3 the correct answer.

Detailed Explanation:

Soil is the primary source of essential mineral nutrients for plants, including nitrogen, phosphorus, potassium, calcium, magnesium, and micronutrients like zinc and iron. These nutrients are absorbed by roots in ionic forms dissolved in soil water.

The atmosphere provides carbon dioxide for photosynthesis, and light drives photosynthesis, but neither supplies mineral nutrients. Chlorophyll is a pigment that captures light energy, not a nutrient source.

Therefore, soil is the main nutrient reservoir for plants, making Option 3 the correct answer.

Detailed Explanation:

Pollination is precisely defined as the transfer of pollen grains from the anther (male part) to the stigma (female part) of a flower. This is the actual act of pollination, distinct from subsequent reproductive processes.

Germination of pollen grains and growth of the pollen tube occur after pollination is complete. Insect visitation is merely a mechanism (agent) of pollination, not the process itself.

Therefore, the transfer of pollen grain from anther to stigma is the correct definition, making Option 4 the correct answer.

Detailed Explanation:

Fungi are heterotrophic organisms that lack chlorophyll, the pigment essential for photosynthesis. Without chlorophyll, they cannot synthesize their own food from sunlight and must absorb nutrients from organic matter in their environment.

They require oxygen (most are aerobic), utilize carbon dioxide in respiration, and grow in various light conditions—thus these components are not lacking. Their cell walls contain chitin, distinguishing them from true plants.

Therefore, chlorophyll is the key component fungi lack, making Option 2 the correct answer.

Detailed Explanation:

Halophytes are plants specially adapted to survive in high-salt environments, tolerating concentrations up to 1M NaCl. Common examples include mangroves and salt marsh vegetation.

Xerophytes thrive in dry/desert conditions, Mesophytes in moderate environments, and Glycophytes are salt-sensitive plants that cannot tolerate saline conditions.

Therefore, salt-loving plants are Halophytes, making Option 3 the correct answer.

Detailed Explanation:

Strontium compounds (like strontium carbonate) emit a bright red colour when heated in fireworks. The heat excites electrons in strontium atoms, which release energy as red light when returning to ground state.

Sodium produces yellow, sulphur burns but doesn't produce metal flame colours, and magnesium gives white light.

Therefore, strontium is responsible for bright red colour in crackers, making Option 4 the correct answer.

Detailed Explanation:

Biogas is produced by anaerobic digestion of organic matter and contains 50–70% methane (CH₄), which is its primary combustible component.

Propane, butane, and ethane are constituents of petroleum gas and natural gas, not biogas.

Therefore, methane is the main constituent of biogas, making Option 4 the correct answer.

Detailed Explanation:

Salt (NaCl) is a non-volatile solute that causes boiling point elevation and freezing point depression through colligative properties—saltwater boils at a higher temperature and freezes at a lower temperature than pure water.

Methyl alcohol (methanol) is a volatile solute with higher vapor pressure than water. When added to water, it increases the overall vapor pressure of the mixture, causing the boiling point to decrease.

Therefore, both statements correctly describe opposite effects due to different solute types, making Option 3 the correct answer.