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.451
Substances whose smell changes in an acidic or basic medium are called olfactory indicators. Which of the following is an olfactory indicator?
- A Clove oil
- B Litmus
- C Turmeric
- D Methyl orange
Show answer
Correct answer: (A) Clove oil
Clove oil, vanilla essence and onion change their smell, not their colour, in acidic or basic solutions, so they are olfactory indicators. Litmus, turmeric and methyl orange are indicators that change colour.
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Q.452
In a household electric circuit, the fuse is connected
- A in parallel with the appliance
- B in series with the live wire
- C in series with the earth wire
- D between the live wire and the earth wire
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Correct answer: (B) in series with the live wire
The fuse is placed in series with the live wire so that when it melts during overloading or a short circuit, the circuit is cut off from the live supply. A fuse in parallel with the appliance or in the earth wire would not stop the current.
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Q.453
Bleaching powder is manufactured by the action of chlorine gas on
- A Limestone
- B Dry slaked lime
- C Gypsum
- D Washing soda
Show answer
Correct answer: (B) Dry slaked lime
Bleaching powder is produced by passing chlorine over dry slaked lime: Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O. The chlorine for this is obtained from the chlor-alkali process.
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Q.454
A cell having 8 chromosomes divides by mitosis. How many chromosomes will each daughter cell have?
- A 4
- B 8
- C 16
- D 2
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Correct answer: (B) 8
Mitosis produces two daughter cells, each with the same number of chromosomes as the parent cell, so each gets 8. Halving of the chromosome number (to 4) happens only in meiosis.
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Q.455
Beriberi is caused by the deficiency of
- A Vitamin C
- B Vitamin D
- C Vitamin B1 (thiamine)
- D Vitamin E
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Correct answer: (C) Vitamin B1 (thiamine)
Beriberi, in which the muscles become weak and there is very little energy to work, is caused by a lack of vitamin B1 (thiamine). Polishing rice removes much of this vitamin, while whole grains, pulses and nuts are good sources.
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Q.456
The law of conservation of energy states that energy
- A can be created but not destroyed
- B can neither be created nor destroyed; it can only change from one form to another
- C can be destroyed but not created
- D of a system always increases with time
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Correct answer: (B) can neither be created nor destroyed; it can only change from one form to another
Energy can only be transformed from one form to another; the total energy before and after any transformation remains the same.
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Q.457
According to the law of constant proportions, in pure water hydrogen and oxygen are always combined in the mass ratio
- A 1 : 8
- B 2 : 1
- C 1 : 16
- D 8 : 1
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Correct answer: (A) 1 : 8
In H₂O, 2 atoms of hydrogen (2 x 1 u = 2 u) combine with 1 atom of oxygen (16 u), so the mass ratio is 2 : 16 = 1 : 8. The ratio 2 : 1 is the ratio of the number of atoms, not of masses.
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Q.458
When an ester or a fat is heated with sodium hydroxide, it gives an alcohol and the sodium salt of a carboxylic acid. This reaction, used to make soap, is called
- A Saponification
- B Esterification
- C Polymerisation
- D Fermentation
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Correct answer: (A) Saponification
Alkaline hydrolysis of an ester is called saponification: CH₃COOC₂H₅ + NaOH → C₂H₅OH + CH₃COONa. Esterification, by contrast, forms an ester from an acid and an alcohol.
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Q.459
Sodium metal is stored under kerosene because
- A it melts at room temperature
- B it dissolves in kerosene to form a useful solution
- C kerosene makes it hard and easier to cut
- D it reacts vigorously with oxygen and moisture in air and can catch fire
Show answer
Correct answer: (D) it reacts vigorously with oxygen and moisture in air and can catch fire
Sodium and potassium are so reactive that they catch fire if kept in the open, so they are kept immersed in kerosene to cut off air and moisture. Sodium does not melt at room temperature, does not dissolve in kerosene and stays soft enough to be cut with a knife.
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Q.460
Calcium (atomic number 20) and argon (atomic number 18) both have a mass number of 40. Such a pair of atoms is called
- A Isotopes
- B Isobars
- C Allotropes
- D Isomers
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Correct answer: (B) Isobars
Atoms of different elements with different atomic numbers but the same mass number are called isobars. Isotopes, by contrast, are atoms of the same element with different mass numbers.
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Q.461
Which of the following was the first fully synthetic fibre, made without using any raw material obtained from plants or animals?
- A Rayon
- B Cotton
- C Wool
- D Nylon
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Correct answer: (D) Nylon
Nylon, prepared from coal, water and air, was the first fully synthetic fibre. Rayon is man-made but is obtained from a natural raw material, wood pulp, while cotton and wool are natural fibres.
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Q.462
Cholera, a bacterial disease, spreads mainly through
- A mosquito bites
- B droplets in the air from coughing
- C contaminated water and food
- D bites of rabid dogs
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Correct answer: (C) contaminated water and food
Cholera is caused by the bacterium Vibrio cholerae, which spreads through water and food contaminated with the faeces of infected people. Safe drinking water and good sanitation prevent it.
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Q.463
The persistence of sound in a large hall due to repeated reflections from its walls, ceiling and floor is called
- A Reverberation
- B Resonance
- C Refraction
- D Interference
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Correct answer: (A) Reverberation
Repeated reflections that make a sound linger are called reverberation. Auditoriums reduce it by using sound-absorbing materials such as fibreboard, rough plaster and heavy curtains.
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Q.464
The food made in the leaves is carried to other parts of the plant, such as the roots and fruits, through the
- A Xylem
- B Stomata
- C Root hairs
- D Phloem
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Correct answer: (D) Phloem
Phloem carries the soluble products of photosynthesis, such as sucrose, from the leaves to other parts of the plant; this is called translocation. Xylem carries water and minerals.
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Q.465
Which of the following methods of preventing pregnancy also helps protect against sexually transmitted diseases?
- A Condom
- B Oral contraceptive pills
- C Copper-T
- D Vasectomy
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Correct answer: (A) Condom
A condom is a mechanical barrier that stops sperms from reaching the egg and also prevents the exchange of body fluids that can carry infections. Pills change the hormone balance, a Copper-T is placed in the uterus and vasectomy blocks the vas deferens; none of these stops infections from spreading.
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Q.466
The raw materials used by green plants for photosynthesis are
- A Carbon dioxide and water
- B Oxygen and water
- C Glucose and oxygen
- D Nitrogen and water
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Correct answer: (A) Carbon dioxide and water
Plants take in carbon dioxide from the air and water from the soil and, using sunlight absorbed by chlorophyll, make glucose; oxygen is released as a by-product. Glucose and oxygen are therefore products, not raw materials.
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Q.467
Amoeba, a single-celled organism, reproduces asexually mainly by
- A Binary fission
- B Budding
- C Spore formation
- D Fragmentation
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Correct answer: (A) Binary fission
In binary fission the Amoeba cell splits into two equal halves, and each half becomes a new Amoeba. Budding is seen in Hydra and yeast, and fragmentation in Spirogyra.
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Q.468
According to Joule's law of heating, the heat produced in a resistor is directly proportional to
- A the square of the current through it
- B the current through it
- C the square of its resistance
- D the square root of the time for which the current flows
Show answer
Correct answer: (A) the square of the current through it
Joule's law gives H = I^2 R t, so the heat is proportional to the square of the current, to the resistance and to the time. Doubling the current produces four times the heat.
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Q.469
The developing human embryo receives nutrition and oxygen from the mother's blood through a special disc-like tissue called the
- A Ovary
- B Oviduct
- C Placenta
- D Cervix
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Correct answer: (C) Placenta
The placenta is a disc embedded in the wall of the uterus. Its villi give a large surface through which glucose and oxygen pass from the mother's blood to the embryo, and wastes pass back into the mother's blood.
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Q.470
Which postulate of Dalton's atomic theory was later shown to be incorrect?
- A Atoms can neither be created nor destroyed in a chemical reaction
- B Atoms combine in the ratio of small whole numbers to form compounds
- C Atoms are indivisible particles
- D The relative number and kinds of atoms are constant in a given compound
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Correct answer: (C) Atoms are indivisible particles
The discovery of electrons, protons and neutrons showed that atoms are made of still smaller particles, so they are not indivisible. The other three postulates still explain the laws of chemical combination.
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Q.471
Which of the following is NOT an example of matter?
- A Air
- B Smell of a perfume
- C Lemon water
- D A thought
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Correct answer: (D) A thought
Matter is anything that has mass and occupies space. Air, lemon water and the perfume particles that reach our nose all have mass and volume; a thought has neither, so it is not matter.
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Q.472
The inner lining of the intestine, where absorption and secretion take place, is made of
- A Squamous epithelium
- B Cuboidal epithelium
- C Columnar epithelium
- D Stratified squamous epithelium
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Correct answer: (C) Columnar epithelium
Tall, pillar-like columnar epithelial cells line the intestine and help the movement of materials across the lining. Simple squamous epithelium lines blood vessels and lung alveoli, cuboidal epithelium lines kidney tubules and the ducts of salivary glands, and stratified squamous epithelium forms the outer layer of the skin.
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Q.473
A rainbow is formed by
- A scattering of sunlight by dust particles in the air
- B reflection of sunlight from the surface of clouds
- C refraction, dispersion and internal reflection of sunlight in tiny water droplets
- D absorption of sunlight by water vapour
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Correct answer: (C) refraction, dispersion and internal reflection of sunlight in tiny water droplets
Raindrops act like tiny prisms: sunlight is refracted and dispersed on entering a drop, reflected inside it, and refracted again on leaving. That is why a rainbow is always seen in the direction opposite to the Sun.
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Q.474
When soap is added to water containing oily dirt, its molecules form clusters called micelles. In a micelle, the hydrocarbon tails of the soap molecules
- A point outwards into the water
- B lie flat on the surface of the cloth
- C point inwards, towards the oily dirt at the centre
- D react with water to form an acid
Show answer
Correct answer: (C) point inwards, towards the oily dirt at the centre
The hydrocarbon tail is hydrophobic and dissolves in oil, while the ionic end is hydrophilic and faces the water. So the tails point inwards around the oily dirt and the ionic ends stay outside, which lets the micelle be rinsed away by water.
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Q.475
In a DC electric motor, the device that reverses the direction of current through the coil after every half rotation is called the
- A Brushes
- B Split-ring commutator
- C Armature
- D Field magnet
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Correct answer: (B) Split-ring commutator
The split-ring commutator reverses the current in the coil every half turn, so the coil keeps rotating in the same direction. The brushes only make sliding contact with the rings, and the armature is the rotating coil with its soft iron core.
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Q.476
Which cell organelle is known as the 'powerhouse of the cell'?
- A Mitochondria
- B Ribosome
- C Golgi apparatus
- D Lysosome
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Correct answer: (A) Mitochondria
Mitochondria release the energy needed for life activities in the form of ATP, so they are called the powerhouses of the cell. Ribosomes make proteins, the Golgi apparatus packages materials and lysosomes digest waste.
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Q.477
The image formed on the retina of the human eye is
- A Virtual and erect
- B Real and inverted
- C Virtual and inverted
- D Real and erect
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Correct answer: (B) Real and inverted
The eye lens is a convex lens and forms a real, inverted image on the retina; the brain interprets the signals so that we see objects upright.
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Q.478
The male reproductive part of a flower is the
- A Carpel
- B Stamen
- C Sepal
- D Petal
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Correct answer: (B) Stamen
The stamen (anther plus filament) produces pollen grains; the carpel or pistil (stigma, style and ovary) is the female part. Sepals and petals are the protective and attractive outer whorls.
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Q.479
Tooth decay starts when the pH in the mouth falls below about
- A 7.0
- B 8.5
- C 5.5
- D 9.5
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Correct answer: (C) 5.5
Bacteria in the mouth break down sugar and food particles left after eating and produce acids. When the pH falls below about 5.5, tooth enamel (calcium hydroxyapatite) begins to corrode; basic toothpastes neutralise the excess acid.
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Q.480
A transformer works on the principle of
- A Electrostatic induction
- B Heating effect of electric current
- C Chemical effect of electric current
- D Electromagnetic (mutual) induction
Show answer
Correct answer: (D) Electromagnetic (mutual) induction
A changing current in the primary coil induces an emf in the secondary coil by mutual induction. Because direct current does not change with time, a transformer works only on AC.
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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.