Defence GK Questions 2026

Nichrome is an alloy of nickel, chromium and iron with a high electrical resistance and a high melting point, and it does not oxidise easily when red hot, so a nichrome wire can glow for years without burning away; that combination makes it the standard material for the heating elements…

Limestone decomposes in the furnace to calcium oxide, a basic flux, which combines with the acidic silica gangue of the ore to form calcium silicate, a fusible slag that floats on the molten iron and is drawn off separately.

In the Mond process impure nickel is heated in a stream of carbon monoxide at a moderate temperature, forming the volatile compound nickel tetracarbonyl; the vapour is led away from the solid impurities and heated more strongly, whereupon it decomposes and deposits very pure nickel.

Galvanisation is the coating of iron or steel with zinc, usually by dipping it in molten zinc.

Pure alumina melts at a very high temperature, so in the Hall and Heroult process it is dissolved in molten cryolite, sodium hexafluoroaluminate, usually with some fluorspar, which lowers the working temperature of the bath and makes the melt a far better conductor of electricity.

German silver is an alloy of copper, zinc and nickel, and its name comes from its white silvery appearance, not from its composition, since it contains no silver at all; it is used for tableware, ornaments and electrical contacts.

Brass is made by alloying copper with zinc, which gives a metal harder than copper, easier to cast and machine, and resistant to ordinary corrosion, so it is used for utensils, taps and fittings and the bodies of musical instruments.

Zone refining rests on the fact that impurities are more soluble in a molten metal than in the same metal when solid.

Calcination is the heating of an ore in the absence or a limited supply of air and below its melting point, so that water of hydration and carbon dioxide are driven off; it is therefore the step used for carbonate ores such as calamine and for hydrated ores such as…

In froth flotation the powdered ore is agitated with water, a frothing agent such as pine oil and a collector.

Galena is lead sulphide, with the formula PbS, and is the principal ore from which lead is extracted; being a sulphide, it is concentrated by froth flotation and then roasted to the oxide before reduction.

Malleability is the property of being beaten into thin sheets and ductility the property of being drawn into wires, and gold possesses both to the highest degree of any metal: a single gram can be beaten into a sheet of about one square metre and drawn into a wire of…

The space agency made the engine by fusing metal powder with a laser and tested it successfully, reducing the number of separate parts in the engine from fourteen to a single printed piece and cutting both the material used and the time taken to build it.

Because the model receives readings from the real machine, building or city as it works, it behaves as the real asset behaves, and engineers can test a change, foresee a failure or plan maintenance on the model without disturbing the original.

The strategy was released by that ministry in 2022 to build a domestic ecosystem for additive manufacturing, covering machines, materials and software, the creation of Indian intellectual property and the skilling of workers, in line with the Make in India and self-reliance programmes.

The country's first 3D-printed post office was built at Cambridge Layout in Bengaluru and opened in 2023, its walls laid down by a concrete printing robot working from a digital design, with technical guidance from an Indian Institute of Technology.

XR is the collective name for augmented reality, virtual reality and mixed reality together, and is used whenever a statement is meant to cover all the technologies that blend the physical world with digital content.

In augmented reality the room, street or object in front of the user stays visible and images, text or sound are added on top of it, as when a camera labels a monument or a windscreen display shows directions.

He popularised the phrase virtual reality in the late 1980s while building and selling some of the first commercial headsets and data gloves, and the name has stuck to the technology ever since.

The novel, published in 1992, uses the word metaverse for a shared virtual city that people enter through goggles and move about in as avatars, and the term was taken up decades later for persistent three-dimensional online worlds.