Class 12 practice
Class 12 gk questions.
GK questions for Class 12, at the level of students aged 15–17, each with its answer and a short explanation. Try each one before opening the answer.
In the extraction of aluminium via the Hall-Héroult process, molten cryolite is mixed with pure alumina. What primary operational purpose does cryolite serve in this electrolytic mixture?
Level 4 of 5Show the answer
Answer: Lowering the melting point of alumina
Pure alumina melts above 2000 °C. Dissolving it in molten cryolite lowers the operating temperature to around 950 °C and increases electrical conductivity, significantly conserving energy.
In C4 plants such as maize and sugarcane, carbon dioxide is initially captured within mesophyll cells. Which enzyme catalyzes this primary carboxylation reaction to form oxaloacetic acid?
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Answer: Phosphoenolpyruvate carboxylase
PEP carboxylase fixes carbon dioxide to phosphoenolpyruvate in mesophyll cells, producing a four-carbon compound. RuBisCO functions in the Calvin cycle inside bundle sheath cells.
In December 1929, the Indian National Congress held its historic annual session on the banks of the Ravi River. This session formally adopted the resolution for Purna Swaraj. Who served as its president?
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Answer: Jawaharlal Nehru
Jawaharlal Nehru presided over the Lahore Congress session of 1929. The delegates declared complete independence (Purna Swaraj) as their goal and resolved to celebrate 26 January 1930 as Independence Day.
Under the standard laws of chess governed by FIDE, what does the fifty-move rule allow a player to do?
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Answer: Claim a draw if fifty consecutive turns pass without a capture or pawn move
According to FIDE rules, a player may claim a draw if the last fifty consecutive moves by each side have occurred without any capture and without any pawn movement.
In optical physics, light traversing a transparent medium undergoes Raman scattering. What happens to the scattered radiation during Stokes scattering?
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Answer: Scattered photons have lower energy and longer wavelength than incident photons
In Stokes scattering, incident photons impart vibrational energy to the medium's molecules. The re-emitted photons consequently carry less energy, which corresponds to a lower frequency and longer wavelength.
Under Article 109 of the Constitution of India, a Money Bill introduced in the Lok Sabha is transmitted to the Rajya Sabha for recommendations. Within what maximum period must the Rajya Sabha return the bill to the Lok Sabha?
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Answer: 14 days
Article 109 of the Indian Constitution mandates that the Rajya Sabha must return a Money Bill within 14 days, failing which it is deemed passed by both Houses.
At the equator, an air parcel moving northward experiences an apparent deflection eastward. Which fundamental physical principle primarily accounts for this apparent deflection when observed from the rotating surface of the Earth?
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Answer: Conservation of angular momentum
As an air parcel travels away from the equator, conservation of angular momentum causes its eastward speed to exceed the ground's rotational speed, creating the Coriolis deflection.
Established in 1986, India's first biosphere reserve spans across the states of Tamil Nadu, Kerala, and Karnataka. Which biosphere reserve is this?
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Answer: Nilgiri Biosphere Reserve
The Nilgiri Biosphere Reserve was established in 1986 as India's first biosphere reserve under UNESCO's Man and the Biosphere programme.
In the blast furnace extraction of iron from hematite, limestone is added alongside coke and iron ore. What is the primary chemical function of the calcium oxide produced from this limestone?
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Answer: Acting as a basic flux to remove silica as slag
Calcium carbonate decomposes into calcium oxide, a basic flux. It reacts with acidic silicon dioxide impurities to form molten calcium silicate (slag), which floats atop the molten iron and is easily separated.
The Chandrasekhar limit establishes a maximum mass threshold for a stable white dwarf star. Above this mass limit, electron degeneracy pressure fails to prevent gravitational collapse. What is this approximate value?
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Answer: 1.4 solar masses
Discovered by Subrahmanyan Chandrasekhar, this threshold is approximately 1.4 solar masses. Beyond it, degeneracy pressure fails, causing the stellar remnant to collapse into a neutron star or black hole.
- True or false?
Total internal reflection takes place when a light ray travels from an optically denser medium to a rarer medium at an angle exceeding the critical angle.
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Answer: True
Total internal reflection requires two essential conditions. Light must travel from a denser to a rarer medium, and the angle of incidence must exceed the critical angle.
- True or false?
Total internal reflection can occur when a beam of light travels from air into diamond.
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Answer: False
Total internal reflection occurs only when light travels from an optically denser medium into an optically rarer medium, such as from diamond into air.
- Fill in the blank.
Each human kidney contains approximately one million microscopic blood-filtering and urine-producing units known as a ___ (First letter: N).
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Answer: nephron
The nephron is the microscopic structural and functional unit of the kidney, comprising a renal corpuscle and a renal tubule.
- Fill in the blank.
Discovered by vaporising graphite with lasers, the spherical allotrope of carbon composed of sixty interconnected atoms arranged in rings is called a ___ (First letter: F).
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Answer: fullerene
Buckminsterfullerene is a cage-like hollow molecule formed by 60 carbon atoms organised into alternating pentagonal and hexagonal faces.
- Fill in the blank.
Under standard International Basketball Federation regulations, the maximum number of players from one team permitted on the court during active play is ___.
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Answer: 5
A regulation basketball squad fields five players on the court at any time, typically comprising guards, forwards, and a centre.
Which of the following three-dimensional geometric figures is the odd one out?
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Answer: Hexagonal prism
The hexagonal prism is a prism, whereas the tetrahedron, octahedron, and icosahedron are regular convex Platonic solids.
A librarian arranges eight distinct volumes on a shelf. Two specific volumes must be separated by at least one other book. How many distinct arrangements of all eight books satisfy this condition?
Level 5 of 5Show the answer
Answer: 30240
Total permutations are 8! = 40,320. Permutations where both volumes sit together equal 2! × 7! = 10,080. Subtracting the together cases yields 30,240 valid arrangements.
The International Court of Justice, seated at The Hague, functions as the principal judicial organ of the United Nations. How many judges constitute this bench, and what is their term of office?
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Answer: 15 judges serving nine-year terms
The ICJ consists of 15 judges elected for nine-year terms by the UN General Assembly and the UN Security Council voting independently.
- True or false?
In C4 photosynthetic plants, the primary carbon dioxide fixation reaction occurs in the bundle sheath cells and is catalysed by RuBisCO.
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Answer: False
Initial carbon fixation occurs in mesophyll cells via PEP carboxylase. RuBisCO operates downstream in bundle sheath cells during the Calvin cycle.
Which of the following legal and constitutional terms is the odd one out?
Level 5 of 5Show the answer
Answer: Ultra Vires
Habeas corpus, mandamus, and quo warranto are constitutional writs issued under Articles 32 and 226 of the Indian Constitution. Ultra vires is a legal doctrine, not a judicial writ.
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