Defence GK Questions 2026

Doping replaces a few host atoms with impurity atoms, and each impurity atom brings its own nucleus along with its electrons, so the total positive and negative charge in the crystal stays balanced.

John Bardeen, Walter Brattain and William Shockley built the first working transistor at Bell Laboratories in 1947 and shared the Nobel Prize in Physics in 1956 for the discovery of the transistor effect.

A full-wave rectifier conducts during both halves of the input cycle, since one pair of diodes handles the positive half and the other pair the negative half.

They are called universal gates because either one of them, used repeatedly, can build every other logic gate, including NOT, AND, OR, XOR and XNOR.

The base of a transistor is made very thin and only lightly doped so that most of the carriers injected by the emitter pass straight through it to the collector instead of recombining in it.

A Zener diode is heavily doped so that breakdown occurs at a low and sharply defined reverse voltage. Beyond that point the voltage across it stays almost constant even when the current through it changes a great deal, which is precisely the property a voltage regulator needs.

A p-n junction conducts freely in forward bias, where the potential barrier is reduced, and blocks current in reverse bias, where only a tiny leakage current flows.

Silicon is the most widely used semiconductor and its forbidden energy gap, the separation between the top of the valence band and the bottom of the conduction band, is about 1.1 electron volts at room temperature.

A p-type semiconductor is made by adding a trivalent impurity such as boron, aluminium, gallium or indium.

An n-type semiconductor is made by doping with a pentavalent element, that is one with five valence electrons, such as phosphorus, arsenic, antimony or bismuth.

A semiconductor has a small forbidden energy gap, so heating supplies thermal energy that pushes more electrons from the valence band into the conduction band, creating more electron-hole pairs.

This Act provides for the declaration of national parks and wildlife sanctuaries, lists protected species in its schedules, and, after the amendment of 2002, added two further categories, conservation reserves and community reserves.

The Harike wetland in Punjab, also called Hari-Ke-Pattan, was formed by a barrage at the point where the Beas joins the Sutlej, is the largest wetland of northern India, and is a Ramsar site rich in waterfowl.

The dugong is a marine mammal that grazes on sea grass, and the sea grass beds of the Gulf of Mannar between Tamil Nadu and Sri Lanka are its principal habitat in India; the Gulf of Mannar was declared the country's first marine biosphere reserve in 1989 and the dugong…

Salim Ali wrote this standard field guide, carried out the bird surveys on which several sanctuaries were notified, and was long associated with the Bombay Natural History Society; the Salim Ali Centre for Ornithology and Natural History at Coimbatore bears his name.

The Convention on Wetlands was signed in the Iranian city of Ramsar in 1971, which is why the sites designated under it are called Ramsar sites; it came into force in 1975, India became a party in 1982, and World Wetlands Day is observed on 2 February to mark the…

Pitti is a tiny uninhabited coral islet in Lakshadweep, notified as the Pitti Bird Sanctuary, and is the breeding ground of sooty terns and other sea birds; it is the only wildlife sanctuary of the territory.

Chilika is a brackish water lagoon on the Odisha coast, the largest of its kind in Asia, separated from the Bay of Bengal by a long sand bar.

Declared in Gujarat in 1980, it was the first area in India to be notified as a marine national park, and it covers a chain of islands carrying coral reefs and mangrove along the Gulf of Kachchh.

Gahirmatha, on the Odisha coast beside the Bhitarkanika mangroves, is the only turtle sanctuary notified in India and protects the world's largest mass nesting ground of the olive ridley turtle, where the phenomenon of arribada, or mass nesting, takes place.