Railway Previous Year GK Questions with Answers

The correct answer is B, acid rain. Rain with a pH below 5.6 is called acid rain. Even clean rain is slightly acidic, with a pH of about 5.6, because carbon dioxide from the air dissolves in it to form weak carbonic acid; that is why 5.6, not 7, is the dividing line. Rain turns more acidic when sulphur dioxide and nitrogen oxides from coal-fired power plants, factories and vehicles mix with water vapour and form sulphuric and nitric acids. Acid rain corrodes marble and metal, kills fish in lakes and harms soil and forests. In India the best-known example is the damage to the Taj Mahal's white marble, often called 'marble cancer'. A is wrong because alkaline rain would have a pH above 7. C is wrong because 'mineral rain' is not a scientific term. D is wrong because hard water means water with dissolved calcium and magnesium salts; it is not a measure of how acidic rain is. Exam tip: rain pH below 5.6 = acid rain; culprits SO₂ and NOₓ; victim marble, as in the Taj Mahal.

The correct answer is C, It protects us from harmful radiation. The ozone layer shields us from the Sun's harmful ultraviolet rays, so when it thins, that protection is lost. It lies in the stratosphere, roughly 15 to 35 km above the Earth, and absorbs most of the UV-B and UV-C radiation. More UV reaching the ground means more skin cancer, cataracts and weaker immunity in people, and damage to crops and to plankton in the sea. The main culprits are chlorofluorocarbons (CFCs), once used in refrigerators, air conditioners and aerosol sprays; a single chlorine atom can destroy thousands of ozone molecules. The Montreal Protocol of 1987 phased these chemicals out. A is wrong because extra UV harms plants and lowers crop yields. B is wrong because ozone loss is about radiation, not the pollution of water. D is wrong because it does nothing to make soil more fertile. Exam tip: ozone layer = Earth's sunscreen in the stratosphere; CFCs damage it; Montreal Protocol 1987; World Ozone Day is 16 September.

The correct answer is D, Forest. A forest forms and runs on its own, without any human effort, so it is a natural ecosystem. Its plants make food by photosynthesis, animals feed on the plants or on one another, and fungi and bacteria break down dead matter and return nutrients to the soil, so the cycle keeps going by itself. Ponds, lakes, grasslands, deserts, rivers and oceans are other natural ecosystems. Ecosystems that people create and have to maintain are called artificial or man-made ecosystems. A is wrong because a crop field is sown, watered, weeded and harvested by farmers. B is wrong because an aquarium is a man-made tank that needs regular cleaning, feeding and aeration. C is wrong because a garden is planted and looked after by people, and left alone it would slowly change into something else. Exam tip: made by nature = natural (forest, pond, desert); made and kept by humans = artificial (crop field, aquarium, garden, park).

The correct answer is B, 010010. The 2's complement of a binary number is found in two steps: flip every bit to get the 1's complement, then add 1. Flipping 101110 gives 010001, and 010001 + 1 = 010010. A quick check confirms it: 101110 is 46 and 010010 is 18, and 46 + 18 = 64, which is 2⁶ for a six-bit number, exactly as it should be. Computers use the 2's complement to store negative numbers and to do subtraction by addition, which keeps their circuits simple. A shortcut also works: copy the bits from the right up to and including the first 1, then flip all the rest. A is wrong because 010011 adds 2 instead of 1 to the 1's complement. C is wrong because 110001 leaves the leftmost bit unflipped. D is wrong because 010001 is only the 1's complement; the final +1 is missing. Exam tip: 2's complement = flip all bits, then add 1; a number plus its 2's complement equals 2ⁿ.

The correct answer is B, To prevent unauthorised access to a private network. A firewall stands between a trusted private network and an untrusted one such as the internet, and checks the data going in and out. Traffic that matches its security rules is allowed and the rest is blocked, much like a guard at a gate. It can be hardware, such as a separate device or a feature of a router, or software, such as the firewall built into Windows. The name comes from the fire-resistant walls in buildings that stop a fire from spreading from one part to another. A is wrong because a firewall does not make the connection faster; checking traffic can even slow it slightly. C is wrong because finding and removing viruses is the job of antivirus software, which works on files already on a computer. D is wrong because storing passwords safely is the work of a password manager. Exam tip: firewall = gatekeeper of network traffic; antivirus = cleaner of infected files.

The correct answer is A, SRAM. Static RAM stores each bit in a flip-flop circuit made of several transistors, usually six, so the bit stays put as long as the power is on and never needs refreshing. That makes SRAM very fast, but also costly and bulky, so it is used in small amounts as cache memory inside the processor. Both kinds of RAM are volatile and lose their data when the power goes off. B is wrong because DRAM stores each bit as a charge in a tiny capacitor that slowly leaks, so it must be refreshed every few milliseconds; it is cheaper and denser, and serves as the main memory. C is wrong because flash memory is non-volatile storage used in pen drives, memory cards and SSDs, and it is slower than RAM. D is wrong because ROM is read-only, non-volatile memory that holds start-up instructions, not a type of RAM. Exam tip: SRAM = static, fast, no refresh, used as cache; DRAM = dynamic, needs refresh, used as main memory.

The correct answer is D, Hard Disk. A hard disk is a secondary storage device that keeps programs and files permanently, even when the power is off, and it sits outside the processor. The CPU (Central Processing Unit), often called the brain of the computer, is made of the Arithmetic Logic Unit, the Control Unit and a set of small, very fast registers. Modern processors also carry cache memory on the same chip to hold the data and instructions they need most often. Data from the hard disk is first loaded into RAM, then moved into the cache and registers before the CPU works on it. A is wrong because the ALU does all arithmetic and logical work such as addition and comparison. B is wrong because the Control Unit fetches and decodes instructions and directs every operation. C is wrong because cache memory is built into the processor chip and is the fastest memory after the registers. Exam tip: CPU = ALU + CU + registers (with cache); hard disk = secondary storage.

The correct answer is A, F5. In Microsoft PowerPoint, pressing F5 starts the slide show from the first slide, whichever slide you are working on at that moment. The same command sits on the Slide Show tab as 'From Beginning'. Its close partner is Shift + F5, which starts the show from the current slide, and paper setters like to place the two side by side. During the show, Esc ends the presentation, and pressing B or the full stop key turns the screen black until you press it again. B is wrong because Alt + Tab switches between open windows in Windows. C is wrong because Ctrl + P opens the Print option in almost every Office program. D is wrong because Shift + F5 begins the show from the current slide, not from the beginning. Exam tip: F5 = start from the beginning, Shift + F5 = start from the current slide, Esc = end the show.

The correct answer is B, Na₂CO₃·10H₂O. Washing soda is sodium carbonate decahydrate: each unit of sodium carbonate holds ten molecules of water of crystallisation. It is made from common salt in steps: baking soda is heated to get anhydrous sodium carbonate, called soda ash, which is then recrystallised from water to give washing soda crystals. It is a basic salt used for cleaning, in the glass, soap and paper industries, and to remove the permanent hardness of water. Paper setters like to put these related compounds side by side as options, so learn them together. A is wrong because NaHCO₃ is baking soda (sodium hydrogencarbonate), used in cooking and in antacids. C is wrong because Na₂CO₃ without water is soda ash, not the crystals called washing soda. D is wrong because NaCl is common salt, the starting material for all of these. Exam tip: NaCl → NaHCO₃ (baking soda) → Na₂CO₃ (soda ash) → Na₂CO₃·10H₂O (washing soda).

The correct answer is A, Red light has a longer wavelength and is scattered the least, making it visible from a distance. Red has the longest wavelength in visible light, about 700 nm, so the tiny particles of air, fog, smoke and dust scatter it the least. The light therefore travels far without fading and can be seen from a distance, which is exactly what a danger signal needs. This follows Rayleigh scattering: the shorter the wavelength, the more the light is scattered. The same idea explains why the clear sky looks blue, since blue light is scattered the most, and why the sun looks red at sunrise and sunset. B is wrong because red light is not more reflective than other colours. C is wrong because how easily a colour is produced has nothing to do with its use in signals. D is wrong because looks are not the scientific reason. Exam tip: longest wavelength = least scattering = red for danger; shortest wavelength = most scattering = blue sky.

The correct answer is D, Potassium. The reactivity series lists metals from the most reactive to the least reactive, and potassium heads it because it loses its single outer electron most easily. It reacts so violently with cold water that the hydrogen released catches fire, so potassium is stored under kerosene. The common order is K, Na, Ca, Mg, Al, Zn, Fe, Pb, (H), Cu, Hg, Ag, Au. A metal higher in the list pushes a lower metal out of its salt solution, which is why an iron nail kept in blue copper sulphate solution gets a brown coat of copper. Metals above hydrogen give hydrogen gas with dilute acids; those below it do not. A is wrong because copper lies below hydrogen and does not react with dilute acids. B is wrong because iron sits in the middle of the series. C is wrong because silver is near the bottom, just above gold. Exam tip: top = potassium, bottom = gold; K and Na are kept under kerosene.

The correct answer is D, Fleming's Left-Hand Rule. It gives the direction of the force, and so of the motion, on a current-carrying conductor placed in a magnetic field, which is exactly what turns the coil of a motor. Stretch the thumb, forefinger and middle finger of the left hand so that they are at right angles to one another. If the forefinger points along the magnetic field and the middle finger along the current, the thumb points in the direction of the force. The force is greatest when the current is at right angles to the field. A is wrong because Ampere's law relates the magnetic field around a closed loop to the current passing through it. B is wrong because the right-hand thumb rule finds the direction of the magnetic field lines around a straight current-carrying wire. C is wrong because Fleming's right-hand rule gives the direction of the induced current in a generator. Exam tip: left hand for motor, right hand for generator; forefinger = field, middle finger = current, thumb = motion.

The correct answer is A, CH₄ + 2O₂ → CO₂ + 2H₂O. Combustion means burning in oxygen, and complete burning of methane gives carbon dioxide, water, heat and light. The equation is balanced: one carbon, four hydrogen and four oxygen atoms on each side. Methane is the simplest hydrocarbon and the main gas in natural gas, CNG and biogas, which is why it burns with a clean blue flame in stoves and vehicles. When oxygen is short, burning is incomplete and poisonous carbon monoxide forms instead of carbon dioxide. B is wrong because it is a substitution reaction: in sunlight chlorine replaces a hydrogen atom of methane, and nothing burns. C is wrong because it is not balanced and shows carbon monoxide, the product of incomplete burning. D is wrong because methane reacting with steam, not oxygen, to give carbon monoxide and hydrogen is steam reforming, an industrial way to make hydrogen. Exam tip: complete combustion of any hydrocarbon gives CO₂ + H₂O + energy.

The correct answer is D, 32. The N shell is the fourth shell (n = 4), and the most electrons a shell can hold is given by the formula 2n², so 2 × 4² = 32. The shells around the nucleus are named K, L, M and N for n = 1, 2, 3 and 4, and the same formula gives them room for 2, 8, 18 and 32 electrons. This is the Bohr–Bury scheme taught in Class 9. One more rule is often tested with it: the outermost shell of an atom cannot hold more than 8 electrons, which is why potassium is written 2, 8, 8, 1 and not 2, 8, 9. A is wrong because 2 is the capacity of the K shell. B is wrong because 8 is the capacity of the L shell. C is wrong because 16 is not the capacity of any shell; the M shell holds 18. Exam tip: remember 2n², so K = 2, L = 8, M = 18 and N = 32.

The correct answer is D, Four. In diamond every carbon atom is joined to four other carbon atoms by strong covalent bonds. These bonds point towards the corners of a tetrahedron and build a rigid three-dimensional network that runs through the whole crystal. That network makes diamond the hardest natural substance, which is why it is used in cutting and drilling tools. Since all four valence electrons are used in bonding, no free electrons are left, so diamond does not conduct electricity. In graphite, the other common form of carbon, each atom bonds to only three others in flat hexagonal layers, and the spare electron lets graphite conduct. A is wrong because two bonds per carbon cannot build a solid network. B is wrong because carbon has a valency of four and cannot form five bonds. C is wrong because three bonds per atom describes graphite, not diamond. Exam tip: diamond = 4 bonds, hard, insulator; graphite = 3 bonds, soft, conductor.

The correct answer is D, New Cartesian sign convention. It is the standard set of rules used for reflection by spherical mirrors and for the mirror formula. Under this convention the pole of the mirror is the origin and the principal axis is the x-axis. The object is always placed on the left, all distances are measured from the pole, distances in the direction of the incident light are positive and those against it are negative. Heights above the axis are positive and below it negative, so a concave mirror has a negative focal length and a convex mirror a positive one. A is wrong because 'system convention' is not a named rule in optics. B is wrong because 'sign convention' is only the general idea; the specific set used is the New Cartesian one. C is wrong because 'mirror convention' is not a recognised term. Exam tip: New Cartesian means measure from the pole; concave f is negative, convex f is positive; mirror formula 1/v + 1/u = 1/f.

The correct answer is B, 2019. Mahatma Gandhi was born on 2 October 1869 at Porbandar in Gujarat, so his 150th birth anniversary fell on 2 October 2019. The Government of India marked it with two years of celebrations from 2018 to 2020, and the Swachh Bharat Mission set its target of an open-defecation-free India for that date. The United Nations observes 2 October as the International Day of Non-Violence, adopted in 2007. Gandhi Jayanti is one of India's three national holidays, along with Republic Day on 26 January and Independence Day on 15 August. A is wrong because 2018 was the 149th anniversary and only the start of the celebrations. C is wrong because 2020 was the 151st anniversary. D is wrong because 2021 was the 152nd. Exam tip: Gandhi born 2 October 1869; 150th anniversary in 2019; 2 October = International Day of Non-Violence.

The correct answer is B, Perini thandavam. Perini Shiva Thandavam is a vigorous warrior dance of Telangana, performed by men in praise of Lord Shiva. It flourished under the Kakatiya kings of Warangal, whose soldiers danced it before going to battle. Its steps are described in the Nritta Ratnavali, written in the thirteenth century by Jayapa Senani, a commander of the Kakatiya army, and dancers carved on the Ramappa Temple at Palampet show its poses. The form had almost died out until the dance scholar Dr Nataraja Ramakrishna revived it in the twentieth century. A is wrong because Bharatanatyam is the classical dance of Tamil Nadu. C is wrong because Sattriya is the classical dance of Assam, begun by Srimanta Sankardev in the Vaishnava monasteries called sattras. D is wrong because Mohiniyattam is the graceful solo dance of Kerala, performed by women. Exam tip: Telangana = Perini; Andhra Pradesh = Kuchipudi; Tamil Nadu = Bharatanatyam; Kerala = Kathakali and Mohiniyattam; Assam = Sattriya.

The correct answer is C, Kachchh. The Kachchh Biosphere Reserve in Gujarat, notified in 2008, covers about 12,454 square kilometres and is the largest biosphere reserve in India by area. It takes in the Great Rann and the Little Rann of Kachchh, salt marshes that flood in the monsoon, and is home to the Indian wild ass, the flamingo breeding grounds and the desert fox. The first biosphere reserve of India was the Nilgiri Biosphere Reserve, set up in 1986 across Tamil Nadu, Kerala and Karnataka. A is wrong because the Sundarbans reserve in West Bengal covers about 9,630 square kilometres. B is wrong because the Gulf of Mannar reserve in Tamil Nadu is about 10,500 square kilometres. D is wrong because Nanda Devi in Uttarakhand is about 5,860 square kilometres. Exam tip: largest biosphere reserve by area = Kachchh (Gujarat); first = Nilgiri (1986); do not confuse it with the largest national park, Hemis in Ladakh.

The correct answer is A, Refuse. The 3 R's of waste management are Reduce, Reuse and Recycle; Refuse is not one of them. Reduce means creating less waste in the first place, such as buying fewer packaged goods and switching off lights to save power. Reuse means using a thing again, like refilling a bottle or turning old clothes into bags. Recycle means sending waste such as paper, glass, metal and plastic to be made into new products. NCERT gives the three in this order, and the order matters: reducing is the best option and recycling the last resort because it still uses energy. Some newer lists add Refuse and Repurpose to make 5 R's, but the paper asks about the 3 R's. B is wrong because recycling is one of the three. C is wrong because reducing is the first R. D is wrong because reuse is the second R. Exam tip: 3 R's = Reduce, Reuse, Recycle, in that order of preference.