12th RJ Board

After the straight hairstyles of the 1920s, waves and curls became the fashion, and a new product was needed to hold hair firmly in place. Women had been using natural compounds such as clays and gums to hold their hair in place for centuries, but it was the invention of the aerosol, can that led to the development of the first hair spray. During World War II, the United States government was looking for a way to spray insecticides to kill malaria-carrying bugs. In 1943, two. Department of Agriculture workers designed an aerosol can pressurized by liquefied gas. Soon, hair spray was produced using the same principle, with a debate still raging over whether it was Chase Products of Broadview, Illinois, in 1948, or Helene Curtis of Chicago seven years later who came up with the idea. Early hair sprays contained polymers (long-chain chemical compounds) that when dry form tiny more...

"I'm quitting. ...I'm going to open up an appliance store, I've always really been into toasters." Dane Cook, actor and comedian In 1919 Charles Strite, a factory worker in a manufacturing plant in Stillwater, Minnesota, became annoyed by the burned toast on offer in the factory canteen and set about trying to solve the problem. Originally, toasting bread would have been carried out over a fire, but labor-saving devices to help with this procedure followed, and the first electric toaster was invented in 1893. It worked by passing electricity through coils of Nichrome" (a nickel-chromium alloy), which caused them to give off heat, thus toasting the bread. Early toasters were sold as a status symbol, even before electricity was common in homes, with the power cord designed to connect to a light socket, the only electrical connection any house would have had. Strite's innovation was to add a clockwork timer more...

“[Electricity] had to be abandoned when no adequate insulators could be found for the wires.” In Paris in 1791, a little-known engineer and inventor named Claude Chappe (1763-1805) began to experiment with an optical signaling system or visual telegraph. His ambition was to send complex messages via a succession of towers using a combination of signaling arms. Three years later, in 1794, working with the aid of his four brothers, Chappe demonstrated his first optical semaphore. His string of fifteen towers placed within sight of each other was able to transmit a message 120 miles (190 km) from Paris to Lille in only nine minutes. The project's burdensome costs were borne by a French leadership who were recently at war with Austria and eager for any strategic advantage in communication, Each tower was topped by a 30-foot (9 m) mast to which a rotating arm was attached with smaller, counterbalanced more...

The invention of the machine gun by Richard J. Gatling (1818-1903) irreversibly changed the face of battle. Gatling took advantage of the newly invented brass cartridge (which, unlike the earlier paper cartridges, had its own percussion cap) to produce the first rapid- fire weapon in about 1862. The Gatling gun consisted often parallel barrels that could fire and reload brass cartridges at rapid speeds through the rotation of a hand-operated crank. With each rotation the firing and loading mechanism of each barrel came into contact with a series of cams. The first cam opened the bolt on the barrel, allowing the bullet to fall into a chamber, while another closed the bolt. A further cam released the firing pin with the final one opening the bolt and ejecting the spent case. The first successful model was deployed in a limited capacity during the American Civil War by Union troops. The more...

"The heroic is for hereafter... for labors of pick and spade by Davy lamp down below." George Meredith, The Amazing Marriage (1895) Miners' safety lamps are still referred to generically as "Davy lamps," after Sir Humphry Davy (1778-1829) who pioneered their design. He was not, however, alone in this endeavor. At the same time as Davy was developing his lamp, railway pioneer George Stephenson and Dr. William R. Clanny were also designing a lamp for miners. The invention of the miner's lamp allowed for penetration to deeper mining seams, by providing light, albeit dim. More importantly, the lamp also gave an indication of the presence of flammable gases such as methane, by its flame burning suddenly more brightly with a blue tinge. It also indicated areas where oxygen was low, by the flame simply extinguishing, and so also functioned as a safety device. The greatest design problem was to create more...

"The atoms become like a moth, seeking out the region of higher laser intensity." Steven Chu, physicist The carbon dioxide laser is considered the most useful and versatile type of laser. It was invented in 1964 by Kumar Patel (b. 1938) while he was working in the United States at Bell Laboratories, New Jersey. Carbon dioxide lasers emit infrared radiation with a wavelength between 9 and 11 micrometers. The active medium in the laser is a mixture of carbon dioxide, nitrogen, and helium. The nitrogen molecules, made to vibrate by an electric current, cannot lose this energy by electron emission, so they in turn excite the carbon dioxide molecules, which produce the laser light. The helium plays two roles; it assists the transfer from the gas of heat caused by the electric discharge, and it helps the carbon dioxide molecules to return to their ground state after excitation. The gas more...

"Age does not diminish the... disappointment of having...ice-cream fall from the cone." Jim Fiebig, columnist In 1846 Williams & Company—a small Philadelphia- based wholesaler of kitchen appliances—purchased the patent for a new hand-cranked machine that could speed up the process of making ice-cream. Over the next thirty years there would be more than seventy improvements to the machine they had shrewdly procured for a mere $200; but what Williams & Company could not buy, however, was the credit for having invented the machine. That distinction belongs  to a humble Philadelphia housewife named Nancy Johnson who lacked both the money and the business savvy to promote her invention and sold the patent to her machine, which went on to be marketed as "Johnson's Patent Ice-Cream Freezer." Nancy Johnson then proceeded to fade quietly back into the obscurity from whence she had come. Johnson's innovative design involved placing the ice-cream's ingredients of more...

Some of the recent events in the country have confirmed that military training should be imparted as a compulsory training to every able-bodied citizen of India. The wars with China and Pakistan and terrorist attacks have compelled the Indian leaders to give a second thought to this problem. Our leaders have realized that in order to meet the challenge, there must be a strong force that could prove to be morale-booster. So, the slogan "militaries the nation" has been coined. Getting training in military science is important and useful in ways more than one. That it makes the people disciplined, is beyond doubt. It also inculcates the noble qualities of service, sacrifice, devotion and dedication. Military training serves as an insurance against foreign attack. It keeps the people physically fit and intellectually sharp. It also increases the power to work. As a matter of fact, by imparting military training compulsorily more...

The car alarm is far from being a universally popular invention: a British television poll listed it as one of the United Kingdom's ten least favorite inventions (just behind the cell phone), and as mayor of New York Rudy Giuliani commented, "Noise pollution is a major problem. Even in a city as exciting as New York, people should be able to sleep without being disturbed by car alarms..." There have been petitions to ban the devices, and there have even been claims that car alarms, far from helping reduce instances of car theft, actually make the problem worse! The first recorded instance of car theft occurred in 1896. Cars are valuable and simple to "disguise," so thieves regard them as easy targets. Reputedly the product of car stereo manufacturers in California in 1970, the car alarm seems to offer the perfect solution; an automated alarm that will emit a loud more...

The mango is a fruit and is popularly known as the 'king of all fruits' in India due to its delicious taste. It is grown in plenty in Mumbai, Tamil Nadu, Bihar, Uttar Pradesh, West Bengal and other states. At the end of January, we can see blossoms in mango trees. At the end of March, these blossoms turn into little green mangoes. They gradually grow bigger. In the months of May and June, they become ripe. At that time they look very beautiful. Their colour becomes golden yellow and sometimes a little red. There are different varieties of mangoes like Bombay, Kishenbhog, Mohanbhog, Langra, Himsagar, Fazli, Bhadhuri etc. We eat mangoes by removing the skin. We also take the juice of ripe mangoes mixed with milk and sugar. The green mango is generally sour to taste. The people of our country cut green mangoes into small pieces and get more...