UPSC 2024 Previous Year GK Questions with Answers

The correct answer is B. The melting point is the minimum temperature at which a solid melts to become a liquid at atmospheric pressure, not the maximum.

At the melting point the particles have just enough energy to overcome the forces holding them in fixed places. Ice melts at 0°C (273 K), and the temperature stays there until all of it has melted, because the heat supplied goes into breaking the arrangement; this hidden heat is the latent heat of fusion. Calling it the maximum temperature is the error the paper setter planted.

A is correct: heating a solid makes its particles vibrate faster, so their kinetic energy rises.

C is correct: steam at 100°C holds the extra latent heat of vaporisation (about 2260 kJ per kg), which is why a steam burn is worse than a burn from boiling water.

D is correct: a gas turning straight into a solid, as frost forms from water vapour, is deposition; the reverse is sublimation.

Exam tip: melting point = minimum temperature for melting; ice 0°C; steam at 100°C carries more energy than water at 100°C.

The correct answer is C, The summer solstice occurs in northern hemisphere on June 21 and on December 21 in southern hemisphere. The two hemispheres always have opposite seasons, so one hemisphere's summer solstice is the other's winter solstice.

On about 21 June the Sun is overhead at the Tropic of Cancer; the northern hemisphere has its longest day and summer begins there, while the southern hemisphere has its shortest day. On about 22 December the Sun is overhead at the Tropic of Capricorn, and the roles reverse: Australia and Argentina have their summer solstice. The cause is the Earth's axis, tilted at about 23.5°.

A is wrong: 21 June is winter solstice only in the southern hemisphere, not in both.

B is wrong: December 21 is winter solstice only in the northern hemisphere.

D is wrong: it swaps the dates; the northern summer solstice is in June, not December.

Exam tip: 21 June = Sun over Tropic of Cancer (northern summer); 22 December = Tropic of Capricorn (southern summer).

The correct answer is C, Radiation. Radiation carries heat as electromagnetic waves, and these waves travel even through empty space.

Heat moves in three ways. In conduction, energy passes from particle to particle in a solid; in convection, a heated fluid itself moves and carries the energy. Radiation needs no particles at all: infrared waves from the Sun cross about 150 million kilometres of near vacuum to warm the Earth. This is also why a vacuum flask can stop conduction and convection but needs a silvered wall to cut down radiation.

A is wrong: conduction needs a material, usually a solid, whose particles pass on vibrations.

B is wrong: convection happens only in liquids and gases, which must flow to carry heat.

D is wrong: collision of particles is the way conduction works inside a medium, so it too needs matter.

Exam tip: conduction = solids, convection = fluids, radiation = no medium (sunlight reaching Earth).

The correct answer is C, extremely fine particles of diameter less than 1 micron. The number after PM gives the upper size limit of the particles in micrometres.

Particulate matter is classed by aerodynamic diameter: PM10 is 10 micrometres or less, PM2.5 is 2.5 micrometres or less, and PM1 is 1 micrometre or less, about one-seventieth of a human hair's width. The smaller the particle, the deeper it travels: PM1 slips past the nose and throat, reaches the alveoli and can even pass into the blood, which is why it is linked with heart and lung disease. Such fine particles come mostly from vehicle exhaust, burning of fuel and crop residue, and industrial smoke.

A is wrong: particles larger than 10 micrometres are coarse dust, not PM1.

B is wrong: the nose traps mainly larger particles; PM1 is too fine to be filtered there.

D is wrong: PM1 is extremely fine, not coarse, and it is the fine particles, not coarse ones, that reach the bloodstream.

Exam tip: PM10 coarse, PM2.5 fine, PM1 ultra-fine; the smaller the number, the deeper it goes into the body.

The correct answer is C: the chamber lets short-wavelength radiation in but does not let long-wavelength infrared out, so heat is trapped.

Sunlight reaching a glasshouse is mostly visible light and short-wavelength (near) infrared, which glass transmits easily. The plants and soil inside absorb it, warm up and re-radiate the energy as long-wavelength infrared, because cooler bodies emit at longer wavelengths. Glass is largely opaque to this long-wave radiation, so the energy stays inside and the temperature rises. In the atmosphere, carbon dioxide, water vapour, methane and nitrous oxide play the role of the glass, keeping the Earth about 33 °C warmer than it would otherwise be.

A is wrong: if no radiation entered, there would be no energy to trap.

B is wrong: it reverses the wavelengths; long waves are the ones held back.

D is wrong: if all infrared could escape freely, nothing would be trapped and no warming would occur.

Exam tip: in short, out long; glass and greenhouse gases stop the outgoing long-wave infrared.

The correct answer is A, 1 only. In January the northern oceans are warmer than the frozen continents, so isotherms bend north over the sea and south over the land; the Gulf Stream and North Atlantic Drift are warm currents, not cold ones.

Isotherms are lines joining places of equal temperature. In the northern hemisphere winter, land loses heat quickly and becomes very cold, while the ocean keeps its warmth. A given temperature is therefore found further north over the ocean and further south over the continents such as Siberia, which makes the lines bend. Statement 2 is wrong: the Gulf Stream and the North Atlantic Drift carry warm tropical water into the North Atlantic, making it warmer, and that warmth is why the isotherms bend sharply north there, keeping ports of north-west Europe ice-free.

B is wrong because statement 2 calls warm currents cold.

C is wrong because statement 2 is false.

D is wrong because statement 1 is a correct inference.

Exam tip: January isotherms bend poleward over oceans and equatorward over land; Gulf Stream and North Atlantic Drift are warm currents.

The correct answer is D, All four. A volcanic eruption throws out solid fragments, fine ash and dust, and a mixture of gases that includes nitrogen and sulphur compounds.

Material released by a volcano is of three kinds. Solid matter includes pyroclastic debris, the broken pieces of rock and lava blown out by the explosion, ranging from large volcanic bombs to small lapilli, along with fine ash and dust that can spread across continents. Liquid matter is the lava. Gases are mostly water vapour, followed by carbon dioxide, sulphur compounds such as sulphur dioxide and hydrogen sulphide, and nitrogen compounds, with smaller amounts of chlorine, hydrogen and argon. Sulphur dioxide forms sulphate aerosols in the stratosphere that can cool the climate for a year or two.

A is wrong because more than one item is a volcanic product.

B is wrong because the gases, not only the solids, come from eruptions.

C is wrong because none of the four can be left out.

Exam tip: volcanic gases = mostly water vapour, then carbon dioxide, sulphur and nitrogen compounds.

The correct answer is A, both statements are correct and Statement-II explains Statement-I. The troposphere is thickest over the equator because strong convection there carries heat high into the air.

The troposphere, the lowest layer of the atmosphere where almost all weather occurs, is about 18 km thick at the equator but only about 8 km at the poles. Intense heating of the surface near the equator sets up powerful rising convection currents, which lift warm air and moisture to great heights and push the top of the layer, the tropopause, upward. Over the cold poles convection is weak, so the layer stays shallow. Temperature in the troposphere falls by about 6.5 °C per kilometre of height.

B is wrong because convection is exactly the reason for the greater thickness.

C is wrong because Statement-II is correct.

D is wrong because Statement-I is correct.

Exam tip: troposphere about 18 km at the equator, about 8 km at the poles, because of convection.

The correct answer is D, Statement-I is incorrect, but Statement-II is correct. The atmosphere is heated mainly from below, by the Earth's own long wave (terrestrial) radiation, not directly by sunlight.

Incoming solar radiation is short wave, and the atmosphere is largely transparent to it, so most of it passes through and heats the Earth's surface. The warmed surface then gives off heat as long wave infrared radiation. Water vapour, carbon dioxide and other greenhouse gases absorb this long wave radiation well, and this is what warms the lower atmosphere. That is also why temperature normally falls with height in the troposphere.

A and B are wrong because Statement-I itself is false, so neither can be the answer.

C is wrong because it reverses the truth: Statement-I is the incorrect one, while Statement-II correctly describes greenhouse gases.

Exam tip: Sun gives short wave radiation that heats the ground; the ground gives long wave radiation that heats the air.

The correct answer is A, Fig. Each fig species is pollinated only by its own tiny fig wasp, and the two have evolved together over millions of years. A fig 'fruit' is really a closed bulb, the syconium, with hundreds of small flowers inside. A female wasp squeezes in through a tiny opening, pollinates the flowers and lays her eggs in some of them. The young wasps grow inside, mate, and the new females fly out carrying pollen to another fig. Without the wasp the fig cannot set seed, and without the fig the wasp cannot breed; this is obligate mutualism. Figs such as the banyan and peepal are keystone species, because their fruit feeds many birds and mammals through the year. Option B is wrong because mahua flowers are pollinated mainly by bats and some birds. Option C is wrong because sandalwood, a root hemiparasite, is visited by many kinds of insects, not one. Option D is wrong because silk cotton (semal) is pollinated mainly by birds. Exam tip: fig and fig wasp are the classic example of co-evolution and obligate mutualism.

The correct answer is D, the average number of live births a woman would have by the end of her child-bearing age. Total fertility rate (TFR) adds up the age-specific fertility rates of women aged 15 to 49 to show how many children a woman would have if she lived through these years at current rates. A TFR of about 2.1 is called the replacement level, because at that rate each generation just replaces itself; the extra 0.1 allows for deaths in childhood. TFR guides India's population policy and is measured by surveys such as the National Family Health Survey and the Sample Registration System. Option A is wrong because the number of births per 1,000 people in a year is the crude birth rate. Option B is wrong because TFR is counted per woman, not per couple, and uses current age-wise rates. Option C is wrong because birth rate minus death rate gives the natural growth rate of population. Exam tip: TFR is per woman, ages 15 to 49, with replacement level 2.1.

The correct answer is A, Canada and the United States of America. Their boundary, about 8,891 km long including the Alaska section, is the longest border between any two countries. It has two parts: about 6,400 km along the southern edge of Canada, much of it along the 49th parallel west of the Great Lakes and through the lakes themselves, and about 2,475 km between Alaska and Canada's Yukon and British Columbia. It is often called the world's longest undefended border and is looked after by the International Boundary Commission. Option D is wrong, though close: the Kazakhstan–Russia border, about 7,600 km, is the longest continuous land border. Option B is wrong because the Chile–Argentina border along the Andes, about 5,300 km, comes third. Option C is wrong because the China–India border is about 3,488 km. Exam tip: Canada–USA is the longest overall, Kazakhstan–Russia the longest continuous land border; India's longest border is with Bangladesh, 4,096 km.

The correct answer is B, 2 and 3 only. Shakyamuni and Tathagata are titles of the Buddha, while Nayaputta is a name of Mahavira. Shakyamuni means 'the sage of the Shakyas', the clan of Kapilavastu into which Siddhartha was born. Tathagata means 'the one who has thus gone', and the Buddha used it for himself in the Pali texts. Nayaputta (Nataputta) means 'son of the Naya or Jnatrika clan', and Buddhist texts call Mahavira Nigantha Nataputta. Option A is wrong because Nayaputta is the one name in the list that does not belong to the Buddha. Option C is wrong because it adds Nayaputta to the two real epithets. Option D is wrong because two of the three names are genuine epithets of the Buddha. Other titles of the Buddha include Sugata and Bhagavat, while Mahavira is also called Jina and Vardhamana. Exam tip: Shakyamuni and Tathagata for the Buddha, Nigantha Nataputta for Mahavira.

The correct answer is C, the lower court prohibiting continuation of proceedings in a case. Prohibition is issued by a higher court to a lower court or tribunal to stop it from acting beyond its jurisdiction. The Supreme Court issues writs under Article 32 and the High Courts under Article 226. Prohibition is preventive: it comes while the case is still pending and stops the lower court from going ahead. Its partner, certiorari, is corrective, because it quashes an order already passed without jurisdiction. Both lie only against judicial and quasi-judicial bodies, never against legislatures or private persons. Option A is wrong because commands to government officers come through mandamus, and prohibition is not issued to administrative authorities. Option B is wrong because no writ can direct a legislature to pass a law. Option D is wrong because it describes no writ; a policy is tested through judicial review. Exam tip: prohibition stops a case midway, certiorari cancels the order after it is made.

The correct answer is D, Dr. Sachchidananda Sinha. As the oldest member, he chaired the Constituent Assembly as its temporary President at its first sitting. The Assembly first met on 9 December 1946 in the Constitution Hall, now the Central Hall of Parliament, and Sinha took the chair following the French practice of letting the senior-most member preside. On 11 December 1946 Dr. Rajendra Prasad was elected the permanent President, with H.C. Mukherjee as Vice-President. Nehru moved the Objectives Resolution two days later, on 13 December 1946. Option A is wrong because C. Rajagopalachari was a member and later Governor-General, not the provisional chair. Option B is wrong because Dr. B.R. Ambedkar chaired the Drafting Committee, set up on 29 August 1947. Option C is wrong because T.T. Krishnamachari was a member of the Drafting Committee. Exam tip: 9 December 1946 first sitting under Sinha, 11 December 1946 Rajendra Prasad elected President.