Defence GK Questions 2026

It receives a very large river inflow from northern Europe, lies in a cool region where evaporation is slight, and exchanges water with the North Sea only through the narrow Danish straits, so its water is brackish rather than fully saline, especially in the Gulf of Bothnia.

The Dead Sea lies in the rift valley of the Jordan river, which flows into it and has no outlet, so dissolved salts have gone on accumulating until the water is several times as salty as the ocean and almost nothing lives in it; its shore is more than four…

It is a northern extension of the Black Sea, joined to it by the Kerch Strait, and its depth nowhere much exceeds a dozen metres, which makes it the shallowest sea on earth; the Don river empties into it.

The Aral Sea is a landlocked salt lake of Central Asia that lost most of its water after the Soviet authorities diverted its two feeding rivers, the Amu Darya and the Syr Darya, to irrigate cotton, leaving salt flats, stranded fishing boats and a ruined local climate; it is the…

This strait at the southern end of the Red Sea, between the Arabian Peninsula and the Horn of Africa, leads into the Gulf of Aden and so to the Arabian Sea, and together with the Suez Canal at the northern end it makes the Red Sea a link in the…

Despite its name it has no outlet to any ocean and is therefore a lake, the largest enclosed water body on earth; it is bordered by five countries, Russia, Kazakhstan, Turkmenistan, Iran and Azerbaijan, and is fed mainly by the Volga.

Lying in the middle of the North Atlantic, it is bounded on all sides by the currents of the North Atlantic gyre rather than by any coast, and it takes its name from the floating Sargassum weed in which European and American eels breed.

This narrow passage between Spain in Europe and Morocco in Africa is the only natural opening of the Mediterranean to the Atlantic Ocean, and it has carried the trade of three continents since antiquity.

It is a marginal sea of the western Pacific Ocean, bounded by the Philippines on the west, Taiwan and Japan on the north and the Mariana Islands on the east, and it is the largest sea on earth; the Mariana Trench, the deepest known point of the ocean floor, lies…

In it nitrogen from the air and hydrogen from natural gas combine directly over a finely divided iron catalyst at high pressure and a temperature of about 450 to 500 degrees Celsius; the ammonia produced is then reacted with carbon dioxide to make urea.

Muriate of potash is potassium chloride, carrying about sixty per cent potash, and it is the cheapest and most widely used source of potassium for crops; the old word muriate simply means a chloride.

Nobel made the dangerously sensitive liquid nitroglycerine safe to transport and use by absorbing it in kieselguhr, a porous earth, and patented the resulting dynamite in 1867; he later combined nitroglycerine with nitrocellulose to make blasting gelatin, and the fortune from these patents endowed the Nobel Prizes.

Gun powder, also called black powder, is made of roughly seventy-five parts potassium nitrate or saltpetre, which supplies oxygen, fifteen parts charcoal, which is the fuel, and ten parts sulphur, which lowers the ignition temperature and speeds the burning.

Replacing part of the soda and lime of ordinary glass with boron trioxide gives a glass whose coefficient of thermal expansion is very low, so it does not crack when heated or cooled suddenly; that is why laboratory beakers, test tubes and ovenware are made of it.

Metal oxides dissolved in molten glass absorb part of the visible spectrum, and cobalt oxide is the standard colourant for the deep blue of bottles and decorative glass, effective in very small quantities.

Cement needs one calcareous material, limestone, for its lime, and one argillaceous material, clay or shale, for its silica, alumina and iron oxide; the mixture is burnt in a rotary kiln at about 1450 degrees Celsius to give clinker, which is then ground with gypsum.

About two or three per cent of gypsum, which is calcium sulphate dihydrate, is ground with the clinker because it slows down the hydration of tricalcium aluminate, the compound that would otherwise set almost the moment water was added and leave no time to place the concrete.

Farmyard manure is the decomposed mixture of cattle dung, urine and bedding litter, and in general it carries only about half a per cent of nitrogen, along with roughly the same order of phosphate and potash.

Nitrogen, phosphorus and potassium are the three primary nutrients, and a fertiliser that carries two or more of them in one chemical compound is called a complex or mixed fertiliser; diammonium phosphate, which supplies both nitrogen and phosphate, and the NPK grades sold by number are the familiar examples.

Superphosphate of lime is made by treating rock phosphate with sulphuric acid, and the nutrient it supplies is phosphorus in the form of available phosphate, not nitrogen; it is therefore a phosphatic fertiliser.