Pariksha SaathiGeneral Studies
General Science: Practice Questions with Answers
480 practice questions on General Science, with answers; most also have an explanation or a worked solution. Try each one before you open its answer.
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Q.151
Which blood vessels have valves that ensure the blood flows only in one direction?
- A Arteries
- B Capillaries
- C Veins
- D Arterioles
Show answer
Correct answer: (C) Veins
Veins carry blood back to the heart at low pressure, so they have thin walls and valves that prevent backflow. Arteries do not need such valves because the blood in them is under high pressure.
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Q.152
The power of a convex lens of focal length 50 cm is
- A +0.5 D
- B -2 D
- C +2 D
- D +50 D
Show answer
Correct answer: (C) +2 D
Power P = 1/f with f in metres. Here f = +0.5 m, so P = 1/0.5 = +2 dioptre; it is positive because a convex lens is converging.
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Q.153
Which blood group is called the universal donor?
- A AB positive
- B A positive
- C B negative
- D O negative
Show answer
Correct answer: (D) O negative
O negative red cells carry no A, B or Rh antigens, so they can be given to a person of any group in an emergency. AB positive, which has all the antigens and no antibodies in plasma, is the universal recipient.
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Q.154
Which of the following is the SI unit of luminous intensity?
- A lumen
- B lux
- C candela
- D watt
Show answer
Correct answer: (C) candela
The candela (cd) is the SI base unit of luminous intensity. The lumen is the unit of luminous flux, the lux of illuminance and the watt of power.
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Q.155
Which instrument is best suited for measuring the diameter of a thin wire accurately?
- A Metre scale
- B Spherometer
- C Screw gauge
- D Measuring tape
Show answer
Correct answer: (C) Screw gauge
A screw gauge measures lengths to about 0.01 mm, so it is used for the diameter of thin wires. A metre scale or measuring tape reads only to about 1 mm, and a spherometer measures the radius of curvature of curved surfaces.
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Q.156
The BCG vaccine is given to protect against
- A Polio
- B Measles
- C Tetanus
- D Tuberculosis
Show answer
Correct answer: (D) Tuberculosis
The BCG (Bacille Calmette-Guerin) vaccine protects against tuberculosis, especially its severe forms in children. Polio and measles are viral diseases with their own vaccines, and tetanus is prevented by the tetanus toxoid vaccine.
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Q.157
Which allotrope of carbon is the hardest natural substance known?
- A Graphite
- B Diamond
- C Fullerene
- D Charcoal
Show answer
Correct answer: (B) Diamond
In diamond the carbon atoms are joined by strong covalent bonds in a rigid three-dimensional network, which makes it the hardest natural substance. Graphite is soft and slippery because its layers can slide over one another.
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Q.158
Which of the following will DECREASE the rate of evaporation of water from wet clothes?
- A Spreading the clothes out
- B A rise in temperature
- C An increase in wind speed
- D An increase in humidity
Show answer
Correct answer: (D) An increase in humidity
When the air already holds a lot of water vapour (high humidity), it takes up less water, so evaporation slows down. A larger surface area, a higher temperature and a stronger wind all increase the rate of evaporation.
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Q.159
Brass is an alloy of
- A Copper and zinc
- B Copper and tin
- C Copper and nickel
- D Iron and chromium
Show answer
Correct answer: (A) Copper and zinc
Brass is copper plus zinc; bronze is copper plus tin; German silver is copper, zinc and nickel; stainless steel is iron with chromium and nickel.
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Q.160
Which molecule is called the 'energy currency' of the cell?
- A ADP
- B DNA
- C RNA
- D ATP
Show answer
Correct answer: (D) ATP
The energy released during respiration is used to make ATP (adenosine triphosphate) from ADP and phosphate. ATP is broken down whenever energy is needed for cellular activities, so it is the energy currency of the cell.
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Q.161
An elderly person who has difficulty seeing both nearby and distant objects is usually advised to use
- A A concave lens only
- B A convex lens only
- C A cylindrical lens
- D Bifocal lenses
Show answer
Correct answer: (D) Bifocal lenses
When both myopia and hypermetropia are present, as often happens in old age, bifocal lenses are used: the upper part is a concave lens for distant vision and the lower part is a convex lens for near vision. A cylindrical lens corrects astigmatism.
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Q.162
Lithium, sodium and potassium form a Döbereiner triad. If the atomic masses of lithium and potassium are 7 and 39, the atomic mass of sodium predicted by the triad rule is about
- A 32
- B 46
- C 16
- D 23
Show answer
Correct answer: (D) 23
In a triad, the atomic mass of the middle element is roughly the average of those of the other two: (7 + 39) / 2 = 23, which matches the actual atomic mass of sodium.
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Q.163
Baking powder is a mixture of baking soda and
- A Washing soda
- B Common salt
- C Plaster of Paris
- D A mild edible acid such as tartaric acid
Show answer
Correct answer: (D) A mild edible acid such as tartaric acid
Baking powder contains sodium hydrogen carbonate and a mild edible acid such as tartaric acid. When it is heated or mixed with water, the acid reacts with the baking soda to release carbon dioxide, which makes cakes and bread soft and spongy.
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Q.164
A car covers the first 30 km of a journey at 30 km/h and the next 30 km at 60 km/h. Its average speed for the whole journey is
- A 45 km/h
- B 40 km/h
- C 50 km/h
- D 35 km/h
Show answer
Correct answer: (B) 40 km/h
Total time = 30/30 + 30/60 = 1 h + 0.5 h = 1.5 h. Average speed = total distance ÷ total time = 60 km ÷ 1.5 h = 40 km/h, not the simple mean of 45 km/h.
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Q.165
The sky appears blue because of the
- A Reflection of sunlight by the sea
- B Refraction of sunlight in the atmosphere
- C Scattering of sunlight by air molecules
- D Dispersion of sunlight by water droplets
Show answer
Correct answer: (C) Scattering of sunlight by air molecules
Tiny air molecules scatter shorter wavelengths (blue) far more than longer ones (red), so scattered blue light reaches our eyes from all directions. The same effect makes the Sun look red at sunrise and sunset.
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Q.166
In a nephron, blood is filtered in the
- A Loop of Henle
- B Collecting duct
- C Ureter
- D Glomerulus
Show answer
Correct answer: (D) Glomerulus
The glomerulus is a cluster of thin-walled blood capillaries inside the cup-shaped Bowman's capsule; blood is filtered here and the filtrate is collected by the capsule. The tubule then selectively reabsorbs useful substances, and the collecting duct carries the urine onward.
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Q.167
To prevent its misuse for drinking, ethanol meant for industrial use is made unfit to drink by adding a poisonous substance such as
- A Glucose
- B Ethanoic acid
- C Methanol
- D Sodium chloride
Show answer
Correct answer: (C) Methanol
Such ethanol is called denatured alcohol. Methanol is poisonous, and even small amounts can cause blindness or death; dyes are also added to colour it blue so that it can be identified easily.
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Q.168
Plasmodium, the malaria parasite, divides into many daughter cells at the same time. This mode of reproduction is called
- A Binary fission
- B Budding
- C Multiple fission
- D Regeneration
Show answer
Correct answer: (C) Multiple fission
In multiple fission the nucleus divides several times and the cell then splits into many daughter cells at once, as in Plasmodium. Binary fission gives only two daughter cells.
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Q.169
Blue crystals of copper sulphate turn white on strong heating because they lose their water of crystallisation. How many molecules of water of crystallisation are present in one formula unit of copper sulphate crystals?
- A 2
- B 5
- C 7
- D 10
Show answer
Correct answer: (B) 5
Hydrated copper sulphate is CuSO₄·5H₂O. On heating it loses these five water molecules and becomes white anhydrous CuSO₄; adding water to it restores the blue colour.
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Q.170
A mixture of common salt and ammonium chloride can be separated by
- A Sublimation
- B Filtration
- C Using a separating funnel
- D Chromatography
Show answer
Correct answer: (A) Sublimation
On heating, ammonium chloride sublimes and its vapour solidifies again on a cool surface, leaving the common salt behind. Filtration cannot be used because both solids dissolve in water.
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Q.171
In an electric generator, the induced current in the rotating coil can be increased by
- A rotating the coil faster
- B using a weaker magnet
- C reducing the number of turns in the coil
- D rotating the coil more slowly
Show answer
Correct answer: (A) rotating the coil faster
The induced current depends on how fast the magnetic field lines passing through the coil change, so it increases with faster rotation, more turns and a stronger magnet. The other three options all reduce it.
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Q.172
Carbon (atomic number 6) forms most of its compounds by sharing electrons rather than by gaining or losing them. The main reason is that
- A forming C⁴⁻ or C⁴⁺ ions by gaining or losing four electrons is very difficult
- B carbon has only two electrons in its outermost shell
- C carbon is a metal
- D carbon atoms cannot form bonds with hydrogen
Show answer
Correct answer: (A) forming C⁴⁻ or C⁴⁺ ions by gaining or losing four electrons is very difficult
Carbon has four valence electrons. If it gained four electrons (C⁴⁻), a nucleus of six protons would find it hard to hold ten electrons, and losing four (C⁴⁺) would need a large amount of energy; so carbon shares its electrons and forms covalent bonds.
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Q.173
Which of the following natural source-acid pairs is correctly matched?
- A Lemon - Lactic acid
- B Curd - Acetic acid
- C Tamarind - Tartaric acid
- D Orange - Oxalic acid
Show answer
Correct answer: (C) Tamarind - Tartaric acid
Tamarind contains tartaric acid. Lemons and oranges owe their sourness mainly to citric acid, and curd to lactic acid.
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Q.174
In the reaction CuO + H₂ → Cu + H₂O (on heating), the substance that gets oxidised is
- A CuO
- B H₂
- C Cu
- D H₂O
Show answer
Correct answer: (B) H₂
Hydrogen gains oxygen to form water, so H₂ is oxidised; copper(II) oxide loses oxygen and is reduced to copper. Since oxidation and reduction occur together, this is a redox reaction.
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Q.175
The inertia of a body depends on its
- A velocity
- B shape
- C volume
- D mass
Show answer
Correct answer: (D) mass
Mass is the measure of inertia: the greater the mass, the greater the inertia. Inertia does not depend on velocity, shape or volume.
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Q.176
Using the rule 2n², the maximum number of electrons that the M shell (n = 3) can hold is
- A 2
- B 8
- C 32
- D 18
Show answer
Correct answer: (D) 18
Maximum number of electrons = 2n² = 2 x 3² = 18. The K, L and N shells can hold a maximum of 2, 8 and 32 electrons respectively.
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Q.177
The phenomenon of electromagnetic induction was discovered by
- A Hans Christian Oersted
- B Michael Faraday
- C Andre-Marie Ampere
- D James Clerk Maxwell
Show answer
Correct answer: (B) Michael Faraday
Michael Faraday discovered in 1831 that a changing magnetic field induces a current in a nearby coil. Oersted had earlier discovered that an electric current produces a magnetic field.
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Q.178
Deficiency of which mineral in the diet causes anaemia?
- A Iodine
- B Calcium
- C Sodium
- D Iron
Show answer
Correct answer: (D) Iron
Iron is needed to make haemoglobin; its deficiency lowers the haemoglobin in blood and causes anaemia, with tiredness and pale skin. Iodine deficiency causes goitre, and calcium deficiency weakens bones and teeth.
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Q.179
Rusting of iron requires the presence of
- A Oxygen alone
- B Water alone
- C Carbon dioxide
- D Both oxygen and moisture
Show answer
Correct answer: (D) Both oxygen and moisture
Rust is hydrated ferric oxide (Fe2O3.xH2O), formed only when both air (oxygen) and water are present; iron kept in dry air or in boiled, air-free water does not rust. Painting, oiling and galvanising keep both away.
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Q.180
Which is the correct and safe way to dilute concentrated sulphuric acid?
- A Add water to the acid quickly
- B Add water to the acid slowly without stirring
- C Mix the acid and water together and heat the mixture
- D Add the acid to water slowly with constant stirring
Show answer
Correct answer: (D) Add the acid to water slowly with constant stirring
Dissolving the acid in water is highly exothermic. Adding water to concentrated acid can make the mixture boil locally and splash acid out, so the acid must always be added slowly to water with constant stirring.
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Q.181
The smell of hot, sizzling food reaches us from several metres away, but we have to go close to cold food to smell it. This is because
- A At a higher temperature, gas particles move faster and diffuse more quickly
- B Cold food does not release any particles
- C Hot food has a higher density than cold food
- D Diffusion of gases does not depend on temperature
Show answer
Correct answer: (A) At a higher temperature, gas particles move faster and diffuse more quickly
A rise in temperature increases the kinetic energy of particles, so the vapours from hot food diffuse into the air much faster. Cold food also gives off particles, but they diffuse slowly.
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Q.182
The aqueous solution of which of the following salts is basic (pH more than 7)?
- A Sodium chloride
- B Ammonium chloride
- C Potassium sulphate
- D Sodium carbonate
Show answer
Correct answer: (D) Sodium carbonate
Sodium carbonate is the salt of a strong base (NaOH) and a weak acid (carbonic acid), so its solution is basic. Sodium chloride and potassium sulphate come from a strong acid and a strong base and are neutral, while ammonium chloride (strong acid, weak base) gives an acidic solution.
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Q.183
Which of the following common name-formula pairs is correctly matched?
- A Slaked lime - CaCO₃
- B Limestone - CaO
- C Quicklime - Ca(OH)₂
- D Caustic soda - NaOH
Show answer
Correct answer: (D) Caustic soda - NaOH
Caustic soda is sodium hydroxide, NaOH. The other three are mixed up: quicklime is CaO, slaked lime is Ca(OH)₂ and limestone is CaCO₃.
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Q.184
During anaerobic respiration in yeast (fermentation), glucose is broken down into
- A Lactic acid and energy
- B Carbon dioxide, water and energy
- C Ethanol, carbon dioxide and energy
- D Acetic acid, water and energy
Show answer
Correct answer: (C) Ethanol, carbon dioxide and energy
Yeast breaks pyruvate down without oxygen into ethanol and carbon dioxide, a process used in brewing and baking. Lactic acid forms in our muscles when oxygen is short, and carbon dioxide and water are the products of aerobic respiration.
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Q.185
Alloys such as nichrome are used in the heating elements of electric irons and heaters because they
- A have a very low resistivity
- B have a high resistivity and do not oxidise (burn) readily at high temperatures
- C have a very low melting point
- D are good insulators of heat
Show answer
Correct answer: (B) have a high resistivity and do not oxidise (burn) readily at high temperatures
A heating element needs a high resistance to produce heat (H = I^2 R t) and must not burn away when red-hot; nichrome has a high resistivity and resists oxidation at high temperatures. Copper and aluminium, with low resistivity, are used for connecting wires.
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Q.186
The tube that carries urine from each kidney to the urinary bladder is the
- A Ureter
- B Urethra
- C Renal artery
- D Collecting duct
Show answer
Correct answer: (A) Ureter
Urine formed in each kidney passes through a long tube, the ureter, into the urinary bladder, where it is stored until it is passed out through the urethra. The renal artery brings blood to the kidney.
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Q.187
The smooth endoplasmic reticulum (SER) mainly helps in the manufacture of
- A Proteins
- B Starch
- C Lipids (fats)
- D Nucleic acids
Show answer
Correct answer: (C) Lipids (fats)
The SER makes fat molecules (lipids), which are used, for example, in building the cell membrane; in liver cells it also helps to detoxify poisons and drugs. Proteins are made by the ribosomes attached to the rough ER.
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Q.188
The bread mould Rhizopus reproduces asexually by
- A Budding
- B Binary fission
- C Fragmentation
- D Spore formation
Show answer
Correct answer: (D) Spore formation
Rhizopus forms round sporangia at the tips of thin threads (hyphae); these release tiny spores which grow into new Rhizopus when they land on a moist surface. The thick walls of the spores protect them until conditions are suitable.
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Q.189
Which connective tissue connects a muscle to a bone?
- A Ligament
- B Cartilage
- C Adipose tissue
- D Tendon
Show answer
Correct answer: (D) Tendon
Tendons are fibrous tissues with great strength but limited flexibility that join muscles to bones. Ligaments join one bone to another, and cartilage smoothens bone surfaces at the joints.
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Q.190
Muriatic acid is the old common name of
- A Sulphuric acid
- B Nitric acid
- C Hydrochloric acid
- D Acetic acid
Show answer
Correct answer: (C) Hydrochloric acid
Muriatic acid is the traditional name of hydrochloric acid (HCl), still used in trade. Sulphuric acid was traditionally called oil of vitriol.
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Q.191
Pure gold is 24 carat. Gold used for ornaments in India is usually 22 carat, which means it contains
- A 22 parts pure gold and 24 parts copper
- B 2 parts pure gold and 22 parts silver
- C 22 parts pure gold and 2 parts copper or silver
- D 22 per cent pure gold and the rest copper
Show answer
Correct answer: (C) 22 parts pure gold and 2 parts copper or silver
Carat is counted out of 24, so 22-carat gold is an alloy of 22 parts pure gold and 2 parts copper or silver. Pure gold is too soft for ornaments, and alloying makes it harder.
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Q.192
Alloys such as brass cannot be separated into their components by physical methods, yet they are classed as mixtures because
- A They are always made of only two metals
- B They show the properties of their constituents and can have a variable composition
- C They are formed by a chemical reaction between metals
- D They have a fixed melting point and a fixed composition
Show answer
Correct answer: (B) They show the properties of their constituents and can have a variable composition
An alloy shows the properties of its constituents and its composition can vary (brass, for example, can have different proportions of zinc), which is why it is a mixture. A fixed composition is a feature of a compound.
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Q.193
The cell theory, which states that all plants and animals are composed of cells, was proposed by
- A Schleiden and Schwann
- B Watson and Crick
- C Robert Hooke and Leeuwenhoek
- D Robert Brown and Purkinje
Show answer
Correct answer: (A) Schleiden and Schwann
Schleiden (1838) and Schwann (1839) proposed that all plants and animals are made of cells and that the cell is the basic unit of life. Virchow later added that all cells arise from pre-existing cells; Watson and Crick worked out the structure of DNA.
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Q.194
Which part of the brain secretes releasing factors that stimulate the pituitary gland to release hormones such as growth hormone?
- A Hypothalamus
- B Cerebellum
- C Medulla
- D Pons
Show answer
Correct answer: (A) Hypothalamus
The hypothalamus secretes releasing factors that stimulate the pituitary gland to secrete hormones such as growth hormone. In this way it links the nervous system with the endocrine system.
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Q.195
What is the pressure exerted by the water alone at a depth of 10 m? (Density of water = 1000 kg/m³, g = 10 m/s²)
- A 10³ Pa
- B 10⁴ Pa
- C 10⁶ Pa
- D 10⁵ Pa
Show answer
Correct answer: (D) 10⁵ Pa
Pressure due to a liquid column P = hρg = 10 m × 1000 kg/m³ × 10 m/s² = 1 × 10⁵ Pa. For the total pressure, atmospheric pressure would be added to this.
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Q.196
When a patient's kidneys fail, the blood is filtered with an artificial kidney. This process is called
- A Haemodialysis
- B Blood transfusion
- C Angioplasty
- D Vaccination
Show answer
Correct answer: (A) Haemodialysis
In haemodialysis the patient's blood is passed through long tubes with semi-permeable linings kept in a dialysing fluid, which removes nitrogenous wastes, and the purified blood is returned to the body. Unlike a real kidney, it involves no reabsorption.
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Q.197
The longest part of the human alimentary canal is the
- A Oesophagus
- B Stomach
- C Large intestine
- D Small intestine
Show answer
Correct answer: (D) Small intestine
The small intestine is the longest part of the alimentary canal and fits into a small space because it is extensively coiled; digestion is completed and most digested food is absorbed here. The large intestine is wider but shorter.
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Q.198
A solid object will float in water if its density is
- A greater than the density of water
- B less than the density of water
- C exactly twice the density of water
- D greater than the density of mercury
Show answer
Correct answer: (B) less than the density of water
When an object's density is less than that of the liquid, it displaces a weight of liquid equal to its own weight before it is fully submerged, so it floats. Objects denser than water sink.
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Q.199
Which of the following statements about action and reaction forces is correct?
- A They act on the same body and cancel each other
- B The reaction is always smaller than the action
- C They act on two different bodies and are equal in magnitude and opposite in direction
- D The reaction begins some time after the action
Show answer
Correct answer: (C) They act on two different bodies and are equal in magnitude and opposite in direction
By Newton's third law, action and reaction are equal and opposite and act simultaneously on two different bodies, so they never cancel each other.
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Q.200
The SI unit of specific heat capacity is
- A J kg^-1
- B J K^-1
- C W m^-1 K^-1
- D J kg^-1 K^-1
Show answer
Correct answer: (D) J kg^-1 K^-1
Specific heat capacity is the heat needed to raise the temperature of 1 kg of a substance by 1 K, so its unit is joule per kilogram per kelvin (J kg^-1 K^-1). J K^-1 is the unit of heat capacity and J kg^-1 that of specific latent heat.
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How these questions were made
Authored by an AI assistant (Claude) from its own general knowledge of stable, well-established facts (no live lookup) - not reviewed by a subject-matter expert; verify against an official source before relying on any fact.