Haryana State Exams

Humphry Davy 0778-1829) first noted the anesthetic effects of nitrous oxide—a colorless, almost odorless gas—while experimenting at the Pneumatic Institute in Bristol, England. Davy (best known for inventing the miner's lamp) realized that nitrous oxide both made him want to laugh (coining the term "laughing gas") and relieved his toothache. In 1800 he published a book stating that the gas might "be used with advantage during surgical operations." After Davy's observations, nitrous oxide became popular at laughing parties and fairground shows, but it was not used in surgery for another forty years. At one fair in the United States, Horace Wells, a Connecticut dentist, observed a man who gashed his leg while under the influence of nitrous oxide. He seemed to be pain-free, and Wells immediately had one of his own teeth removed while breathing in the gas. In January 1845, Wells demonstrated the use of nitrous oxide in a more...

The most sticky, hot, and humid places in the world tend to be found in Southeast Asia, near coastal regions around the equator. Anyone who is not used to the heavy, damp, often motionless air can find them to be very uncomfortable places to live. Humidity, the moisture content of the air, tends to be high in these places because the heat of the sun causes the air to absorb increased moisture from the surrounding seas and oceans—the air in cold latitudes is relatively dry. But it was not until the 1600s that people were able to measure air humidity. Technically, Leonardo da Vinci designed the first crude hygrometer in the 1440s, but in 1664 the first practical hygrometer, used to measure the moisture content of air, was invented by the Italian scientist Francesco Folli (1624-1685). Folli's invention was a finely decorated device, made of brass, that contained a mounted more...

Delhi has always created its own history. It has wonderful monuments and architectural heritage. It has wide roads and a number of flyovers, the unique Red Fort, Rashtrapati Bhawan, Qutub Minar, Chandani Chowk are some of its great glories. Metro is its crowning glory which adds a new speed to its progress.   Delhi MRTS (Delhi Mass Rapid Transit System) or Delhi Metro is a rapid transit system in Delhi operated by the Delhi Metro  Rail Corporation Limited. With a view to reducing the problems of the Delhi commuter, the launching of an Integrated Multi Mode Mass Rapid Transport System for Delhi had long been under consideration. The first concrete step in this direction was however taken when a feasibility study for developing such a multi modal MRTS was commissioned by GNCTD (with support from GDI) in 1989 was completed by RITES in 1991. It recommended a 198.5 km predominantly more...

Population of a region means the number of people living in that region, in which they share their basic needs like land, water and other resources. The whole of the world has 71% water while only the rest has the conditions to sustain life, meaning here by we have a very little of land to live on. In the same way, we have other resources for our use. Resources are very limited while the population is growing rapidly. The world population has almost doubled in 40 years from 3 billion in 1961 to 6 billion in 2001. The situation is greatly alarming. At the time of independence, India's population was not more than 40 crores. In a span of 57 years, we have multiplied manifold. The present number is very grim and critical. India, a developing country has one of the largest reservoirs of natural resources but is still lagging more...

"In the mid-1980s... music networking through things called audio cassettes was at its peak." Carl Howard, alternative music network pioneer Like SMS (short message service) text messaging three decades later, the audiotape cassette (or "compact cassette," to give it its official name) is a classic case of an innovation created for one purpose that finds unexpected success for another. Although the cassette (derived from the French word meaning "little box") was an audio storage medium, Philips saw little potential for its use within the high-fidelity music market. It had, in fact, been designed primarily for use in dictation machines and cheap portable recorders. Introduced in 1963, the cassette slowly established itself in the decade that followed. Its success was largely due to Philips's decision to license aspects of their technology free of charge. The tape used in the early cassette cartridges was thin, low-quality, and only half the width of more...

Hunting is of many types. Someone hunts with the eyes, the fair sex. Sportsman hits the ball with foot, stick or a bat. Soldiers hunt the life of the enemy's army. Pickpocks hunt for the pockets of others. Underworld mafias hunt for the life of their counterparts Dacoits and thieves hunt for the money which some rich people have. A person who is fond of drinking hunts for a bottle of whisky to quench his thirst. So every member of the society is hunting for one thing or the other. To overcome the problems of the food man started hunting animals. After sometimes hunting was looked upon as a spor) though for royal and noble families. He hunted all types of animals as adventurous deed. But man soon got bored of hunting as it became a one sided affair in the age of modern equipments and latest modernized rifles which more...

More than a million years ago, members of the species Homo erectus were making stone tools designed for chopping that can be described as early hand axes. They were teardrop-shaped and roughly made, flaked on either side to form a sharp cutting edge. However, not until the rise of farming during the late Stone Age did such tools come to resemble what we would now recognize as the axe. There was widespread trade in these tools around this time and stone axes have been uncovered at many Neolithic meeting places. Axes clearly designed to be mounted (hatted) on handles have been found at a site near Mount Hagen in New Guinea. By analyzing samples of pollen from around the same era—thought be around 8,000 years ago—archeologists have concluded that they were probably employed in the opening up of the rain forest, during agricultural development, to allow light to reach crops. more...

Many people have sacrificed their lives to quench the thirst for knowledge and to satisfy his curiosity to gain knowledge. In the Olden days people used to worship sun and moon thinking them sacred heavenly bodies. But the scientific investigation had proved that sun is an ordinary star and moon is a planet like other planets. After this the man has entered the age of the space travel. The invention of-rocket was the first step in space travel. Scientists had already discovered that there was neither air nor water on the moon. The moon was the first target of the man. The moon is our nearest neighbor. It is about 300000 kms from the earth. A space ship travelling at a speed of 4000 kms/hour can cover this distance in 10 hours. The scientists had further discovered that the surface of moon is rough and full of craters, rocks and more...

The origins of the spinning wheel remain unsure, but the machine is thought to have been invented around 700 in India, where it was used to turn fibers into thread or yarn that were then woven into cloth. Earlier hand-spinning methods were superseded by mounting the spindle horizontally and rotating it by slowly turning a large wheel with the right hand. The fiber was held at an angle in the operator's left hand to produce the necessary twist. The spinning wheel reached Europe in the Middle Ages, becoming part of a cottage industry that used simple hand-operated tools. It persisted in this context until the eighteenth century. In Britain the new cotton industry was modeled on the old woolen cloth industry. The most complicated apparatus was the loom, worked by a single weaver and normally kept in an upstairs room where a window provided natural light. The weavers were usually more...

"What is life? It is a flash of a firefly in the night. It is the breath of a buffalo in the wintertime…” Crowfoot, chief of the Blackfoot First Nation Native Americans on the Great Plains led nomadic lives. They used buffalo for almost everything, eating their meat and making clothes and tent coverings from their skins. Living on herds of animals that were always on the move, they were constantly on the move too, which meant living in tents and owning only what could be carried to the next camp. Ideally, however, people like to carry more than can fit into one bag. On roadways and hard ground, carts are the best solution, and in the far north snow and ice lie on the ground and dragging a sled is easy because the ground is slippery. Traveling across soft soil, however, neither of these options work. The response of more...