1.What is electricity? 

Electricity means the flow of electric power or charge. It is a physical phenomenon related to stationary or moving electrons and protons. It includes phenomena like lightning, static electricity etc. It is a form of energy constituted of the flow of electrons.  Lightning 

2.What is electric current? 

Profons Nucleus Neutrons Everything is made up of atoms. The centre of an atom contains a nucleus, which has positively charged protons and uncharged neutrons. The nucleus is surrounded by negatively charged electrons. The number of protons, electrons and neutrons in an atom is usually equal. When this balance between electrons and protons is disturbed by an outside force, an atom might lose or gain an electron. This causes the electrons to move freely from one atom to another which is called electric current. Electrons

Measurement of Electricity

1.How is electricity measured? 

CON  What  The unit of power used to measure  to honour the inventor of steamet  electricity is called Watts. It was a  James Watt. However, one walt is  A cons  allow  throu  mate  boun  from  the  thro  thes  elec  Wh  ele  very small unit of power. 

2.What is horsepower? 

James Watt About 750 watts of power  would equal one horsepower. This term  was devised when steam engine was  invented. It was used to compare the  output of steam engines with the power of  horses used for the same work. It is used  to measure the power of piston engines,  turbines, electric motors etc. 

3.Are any other units used to measure electricity? 

V  Volt: It is used to measure the quantity of  electric potential at a point.  Ohm: It is used to measure electrical  resistance  Ampere: It is the amount of electric charge  A  passing through a point per unit.  Sil  Aft  Andre More  Ampere  12  FACT  One megawatt is equal to 1000 kilowatts. The world consumes about  billion megawatts of electricity per year.  50 SCIENCE      


Various kinds of sounds which we hear, from a whisper to a roar, are nothing but simply moving air. When a sound is made, it causes vibrations in the air. These vibrations carry the sound to our ears. The vibrations that carry sound through the air are called sound waves. In other words, sound is the transfer of energy in the form of waves. The waves travel by bumping air molecules together. The air molecules move back and forth, but the wave of energy moves outwards. The speed with which the waves travel through air depend solely on temperature. Sound waves travel faster through solids and liquids rather than through air. The reason behind this is that the molecules are densely packed together in liquids and solids. There is complete silence in space because there are no molecules to carry the sound waves. Sound travels with a speed of about 344 m/s in air at 20 degrees Centigrade. It travels faster in warm air reaching the speed of about 386 m/s at 100 degrees Centigrade. It travels at 1500 m/s in water.


A jet flies by gathering quickmoving air in its inlets. The incoming oir is squeezed in with the help of rotory fans. Fuel is squirted into the com- pressed air which burns the midure. As a result, the hot, burnt goses are pushed towards the back and the Å¿et moves forwards Intense rain or hail may cause the combustor to bum the air-fuel mixture less efficiently. Usually, this effect is negligible because the intense period of a storm is generally brief. Normal rain, hail or snowstorms do not produce enough water. Even if they do so, the high temperatures in the combustion chamber evaporate the moisture. The water only adds a slight amount of steam to the burning air-fuel mixture and doesn’t reduce the engine power apparently. Further- more, the engine is designed in such a way as to extract excessive water, snow or hail from the air before it reaches the combustion chamber. This is howo jet continues to function with snow,hail, or rain falling all around it.


When you look at the photogrey sunglasses, they’re as clear as glass. As you step outside in the sun, the glasses darken and block up to 80 per cent of the light radiation within a minute. Isn’t it surprising? The sun. glasses can change colours under light (photochromic material) because of a special manufacturing process. When the glass is molten, the tiny, transparent crystals of silver halide are added to it. The silver-halide crystals change chemically when the substantial amounts of ultraviolet light hit the glasses. The silver ions in the crystals combine with an electron to form silver atoms inside the glass. The silver blocks light and the glasses darken. The stronger the ultraviolet, the darker the Halogen gas which is released when the silver ions formed atoms cannot escape the glass. When you remove the glasses by stepping inside, the trapped halogen gas atoms recombine with the silver atoms and form clear silver-halide crystals once more. The dark glass clears and becomes trans-parent again.


A safety glass is a type of gla that, when struck, breaks in finy, relatively harmless fra ments rather than shatterin into large, harmful pieces Safety glasses may be made in two ways. They may be constructed by laminating the two sheets of ordinary glass together with a thin interlayer of plastic. They may be produced by strengthening glass sheets by heat. Good quality safety glasses are made from polycarbonate and are shatter resistant. It doesn’t mean that they are unbreakable or that they lost for ever. Their purpose is to protect the wearer from an injury that may result due to accidental projectiles and particles. Although safety lenses may be constructed from a variety of materials of various impact resistances yet, certain standards suggest that they must maintain a minimum 1 millimetre thickness at the thinnest point. Safety glasses can vary in the level of protection they provide. The safety glasses used in a factory must have stronger lenses and a stronger frame with additional shields at the temples, whereas the safety glasses used while welding have much darker lenses.


Waxes may be natural and artificial Natural wax is a substance that is secreted by bees and used by them in constructing their honeycombs. In addition to beeswax, carnauba (epicuticular wax of a plant) and paraffin lo petroleum wax) are waxes which occur naturally Artificial waxes are esters. It means that they are the combinations of long chain of alcohols and long chain of fatty acids. Wax is used in several ways:-
1. As a water-resistant coating on cars and furniture.
2. They are used in lipsticks and eyebrow pencils, in liquid soaps and shampoos to give a pearl-essence effeci.
3. Lanolin is a wax made by sebaceous glands of sheep. It is washed out of wool with detergents. It is used in many hair and skincare products,
4. Waxes are made into candles, but most candles these days are made from a long chain of hydrocarbons (called paraffin) which are not true waxes.
5. Waxes are the principal component in traditional varnishes such as shellac.


We observe that when a metal objed is brought close to o magnet, it gets attracted and sticks onto it. This happens because when a metal objec is brought close to a magnet, it makes a line of force. This line of force is not visible to the human eye, but it can be felt by a simple experiment. If we put iron particles on a thin piece of poper and put that paper on the magnet, the iron particles will fall exactly in the area of the line of force. This line of force is known as the “magnetic field. The points of which the iron particles are attracted to the magnet are known as the magnetic poles. All magnets have two ends, usually marked “north’ and “south”. The fundamental law of all magnets is: Opposites attract and likes repel. So, if you have two bar magnets with their ends marked “north and south, the north end of one magnet will attract the south end of the other. On the other hand, the north end of one mog net will repel the north end of the other


An electric toaster changes electrical energy to heat energy. Inside the appliance are the loops of special mixture of metals. Nichrome, a nickel- chromium alloy, is one of them. Electricity cannot pass through this special metal very easily. The metal slows down the electrons and holds up the current flowing through it. This is called the “resistance of the metal. When the resistance of a metal is higher, the metal gets hot because of the friction of the electrons in the current of electricity. As the electricity is forced through the wires, the wires begin to heat up and glow very hot causing the bread to become brown. At the same time, a bimetallic strip heats and expands. One of the two metals in this strip expands more quickly than the other causing the strip to curve. As it bends, il completes an electrical circuit and activates an electromagnet. The magnet attracts a catch and releases the spring that holds the racks in
the toaster. The elements switch off and the toasted slices pop up.


A thermometer is a device that measures the temperature of a person’s body, the air etc. The name is made up of two smaller words: “thermo” means heat and “meter” means to measure. There is usually a bulb of the base of the thermometer with a long glass tube stretching out to the top. Early thermometers used water. As water froze, there was no way to measure temperatures less than the freezing point of water. So, alcohol, which freezes at temperature below the point where water freezes, was used. The red coloured or silver line in the middle of the thermometer moves up and down depending on the temperature. When you look at a thermometer, you’ll see a thin red or silver line that grows longer when it is hotter. The line goes down in cold weather. This liquid is sometimes coloured alcohol but can also be a metallic liquid called mercury. Both mercury and alcohol grow bigger when heated, whereas they grow smaller when cooled. Numbers are placed alongside the glass tube that mark the temperature when the line is at that point.


che col reaction proces where in the chemical properties to ceare red by the rearrangement of the consthe once A che alreaction occurs when bonds between os made or brokeThere are derent types of chemical reactions When wood bums in the presence of oxygen, is fumed to ash becomes an entirely different mixture than it was before Obviously, the ashes cannot be simply froren totum them back into wood again. This is an example of on irreversible chemical reaction Chemical reactions may also malve changes in colour. In specific proportions and under the night conditions, carbon which is block con be combined with colourless hydrogen and orygen to produce white sugar Chemical reactions which give off heat are called Brothermic reactions. The speeds of reactions are determined by lodon ke temperatures around and the and shopes of readonts


Anything which happens from the drop of a pin to an explosion requires energy Energy is defined as the ability to put effort and enthusiasm into a piece of work and work is defined as the use of energy to do work. There are various forms of energy like heat, light, sound, electrical, chemical, nuclear, potential and kinetic energies. The Law of the Conservation of energy states that the total amount of energy in the Universe is fixed. Energy can neither be created nor destroyed; it can only be transferred or changed into one form or another. For example, an object gains potential when it is lifted. As soon as the object is released, potential energy is transferred into the energy of motion or kinetic energy. During this transference, some of the energy is converted into heat energy.


Force is a push or pull exerled upon an object due to its interaction with another object. Whenever there is an interaction between two objects, there is a force upon each of the objects. In other words, in order to make a stationary object move or a moving object stop, force is required. There are various types of forces. For simplicity, all forces are divided into two groups contact forces and adion-at-a-distance forces Contact forces are types of forces in which the two interaching objecis are physically in contact with each other. Action-of-a-distance forces are types of forces in which the two interacting objects are not in physical contact with each other. Still, they are able to exert a push or pull. Examples of action-at-a-distance forces include gravitational forces (e.g., the sun and planets exert a gravitational pull on each other in
spite of their large separation) and magnetic forces (e.g., two magnets can exert a magnetic pull on each other even when separated by a distance of a few centimetres).


A remote control electronic device is used lo the remote operation of machine. Remote control are used to issue commar from a distance to televi. sions or other consumer electronics such as stereo systems and DVD players usually small They are wireless hand-held objects with a number of buttons for adjusting various settings such as surfing television channels, tracking numbers and the adjustment of olume. A remote control for an electronic appliance ses an infrared to emit a beam of light that reaches the evice. This light is invisible to the human eye but carries ‘nals that are detected by the appliance. When a person esses a button on his/her remote control, it tells a tiny computer processor to trigger a RUNOS OS light emitting
device called a diode which is located at the front of the remote. The diode, then, sends an infrared signal to o light sensitive area called photocell on the person’s T.V. set. These repeated light signals are five times a second


Basically, a Compact Disc(CD) is nothing more than a plastic (polycarbonate) disc with several layers. It is principally made up of injection-moulded polycarbo-nate. The diameter of a CD is about 12 cm and is about 1.2 mm thin. A CD has a track of tiny pits in a silvery reflective layer on a plastic disc. It is read by a laser which enters the CD on the play side, travels through the CD’s clear plastic layer and picks up information from the layer data on the silvery surface between the pits. Then, the laser bounces off the reflective coating on the back side of the data layer. The reflected laser beam, then, travels back through the clear plastic layer, out of the CD, and into the “detector” of the CD player. As the CD rotates, the information is translated into a sequence of signals. These signals are interpreted by the detector as strings of zeros and ones. QATAR
and Other Related information Parlem Dance for you and your inte


When air moves quickly over a surface The basic principle of flying a kite has to do with a difference in air pressure. the pressure is decreased. When it increased. A kite flies because it deflects the wind downwards and the resulting change in momentum produces an upward force. The reason for this is that the air travelling over the top of the curved surface of the kite is going faster than the air passing underneath. Fast moving air creates less pressure; this means there is more pressure underneath the kite. This helps to force it upwards. The kite string keeps the kite at an angle of attack to the wind. The wind hits the kite and flows down the path of least resistance. The air exerts an equal and opposite upward force on the kite and the kite rises due to this lift. In other words, the kite blocks the wind. Then, the kite pushes down on the air. Finally, the air pushes back up on the kite and lifts it into the sky KNES


The world’s first cast iron bridge was built over River Severn in Coalbrook-dale, Shropshire, in 1779 It was the first bridge ever to be built of iron. It is perhaps the most important indust- rial monument in Britain. It attracted visitors from all over the world. The bridge was designed by Thomas Pritchard and built by Abraham Darby. The technique of smelting iron with coke was perfected by Abraham Darby, who used the product to build the bridge. As soon as the bridge was built, a community started to form around it and the town of Ironbridge vas born. The semicircular arch of the bridge spans 100.5 feet (30.6 m) and has five arch ribs, each cast in two halves. All the major part-
were put together in three month without a single accident or the leas obstruction to the boats in the river. was the industrial revolution whic brought about the beginning of met bridges. Previously, bridges we constructed of stone and timber.


A submarine is watercraft thot con operate underwater ranges from otwo man vessel, which examine the sea floor for a few hours to the Russian Typhoon class, which can remain submerged for 6 months and carry nuclear missiles capable of destroying multiple cities. William Boume, a British mathematician, drew plans for a submarine in 1578. It was only in 1620 that Comelius van Drebbel, a Dutch inventor, managed to build a submarine. He wrapped a wooden rowboat tightly in waterproofed leather and had air tubes with floats to the surface to provide oxygen. He took the first trip with 12 oarsmen in River Thames and stayed submerged for 3 hours. The first submarine used for military purposes was built in 1776 by David Bushnell of ihe US. His “Turile was a one man, wooden submarine powered by hand turned propellers. It was used during the American Revolution against British warships. The Turtle would approach the enemy ship partially submerged to attach explosives to the hull of the enemy ship.


A battleship is a large, heavily armoured warship with a main battery consisting of the largest calibre of guns. Battleships were larger, better armed and better armoured than cruisers and destroyers. The last battleships were withdrawn from service in 2006. Yamato, the largest battleship ever built, was named after the ancient Japanese Yamato Province. It was a battleship of the
Imperial Japanese Navy during World War II. The design of this super battleship (class of warships) was initiated by Japan’s Naval General Stati in 1934. The construction of the Yamato began after the Japanese had withdrawn from the Washington Naval Treaty at the Second London Conference of 1936. It had nine 460mm (18.1- inch) main battery guns which fired 1460kg (3,200 pounds) armour piercing shells. These guns were the largest battleship guns ever to go to the sea. The Yamato was completed soon after the Japanese attack on the U.S. base at Pearl Harbor on 7th December 1941. It was a huge battleship. It had 200,000 horsepower turbines which gave it a top speed of 31 knots and a range of 7,200 miles. It hosted a crew of 2,747 officers and men.


there is a type of satellite her amarily used to monitor the er and climate of the Earth. The weather stelle, Vanguard 2, launched on 17th February 959 was designed to measure oder and resistance, but the por out of rotation kept it from colecting a notable amount of useful Bet The first weather satellite to be Considered a success was TIROS-1, Lounched by NASA on 1st April, 1960. This marked the first day when it become possible to observe the Earth’s weather conditions on a regular basis. The satellite designed to obtain the pictures of clouds was rocketed into space aboard a Thor- Able launch vehicle on 1st April, 1960, from Cape Canaveral, Florida. The satellite was basically a cylinder with 18 flattened sides to mount solar power cells. The satellite was approximately 42 inches in diameter, 22 inches high (including the projecting television camera lens) and had a lounch weight of approximately 128.4kg including fuel for small solid rockets to control the spin-over time of the satellite TIROS-1 operated for 78 days.

Science and technology


  A fax machine is a device that can send or receive pictures and text over a telephone line Fax machines have been around in one form or another for more than a century but it was Alexander Bain who patented the first fax design in 1843. A fax machine consists of an optical scanner for digitizing images on paper, a printer for printing incoming fax messages and a telephone for making the connection, Fax machines work by digitizing an image – dividing it into a grid of dots. Each dot is either on or off, depending on whether it is black or white. Electronically, each dot is represented by a bit that has a value of either O (off) or 1 (on). In this way, the fax machine translates a picture into a series of zeros and ones (called a bit map) that can be transmitted like normal computer data. On the receiving side, a fax machine reads the incoming data, translates the zeros and ones back into dots and reprints the picture. While sending documents to people at large distances, faxes have a distinct advantage over postal mail in respect that the delivery is instantaneous.


  A Bunsen burner is a laboratory device designed to heat substances for various experiments. It is a gas burner used in laboratories because it provides a hot, steady, smokeless flame. Bunsen burner was invented by Robert Wilhelm Bunsen in 1855. Bunsen (31st March, 1811-16th August, 1899) was a German chemist and teacher. He invented the Bunsen burner for his research in isolating chemical substances. Peter Desaga who passed from the University of Heidelberg (where Bunsen worked) was a mechanic. He built the first Bunsen burner to Bunsen’s specifications. The design of a Bunsen burner includes a vertical metal tube which is connected to a weighted base. The base includes a nozzle to connect with a fuel source, as well as a gas valve nd a flame adjuster to control how much air is admitted through small ir-holes at the base of the tube. The gas mixes with air at the bottom of the tube and then rises to the top of the Bunsen burner, where it can be lit with a matchstick or lighter 


 Radar (Radio Delection And Ranging) is a system that 1965 aledramagnelle waves to identify the range, altitude, direction or speed of both moving and fixed objects such as alreroli, ships, maior vehicles Rader signala bounce of objects in their path and the roder system deles ha achoes of signals that return, Radar can determined number of properties of a distant object, such as its distones, spsed, direction of motion and shops One of the primary uses of rodor is air tralhe control, both civilian and military large nelworks of ground-based radar systems help air troflic controllers keep track of aircraft and prevent midoir collisions. Military forces around the world use rodar to delect aircraft and missiles, troop movement and ships of sea, as well as to forget various types of weapons, Meteorologists use radar 10 observe and forecast the weather. Other scientists use radar for mapping the surface of the earth from orbit, studying asteroids, investigating the surfaces of othe- planets and their moons, and 


 The Internet, sometimes called simply the Nel,” is a worldwide of computer networks in which users at any computer can, if they have system 1 permission, get information from any other computer and can also tolk directly to users at other computers . The Internet is composed of many interconnected computer nelworks. Each network may link tens, hundreds, or even thousands of computers, enabling them to share information and processing power, The Internet has made it possible for people all over the world to communicate with one another effectively and inexpensively. Unlike traditional broadcasting media, such as radio and television, the Internet does not have a centralized distribution system. Instead, an individual who has Internet access can communicate directly with anyone else on the Internet, post information for general consumption, retrieve information, use distant applications and services, or buy and sell products. Each computer connected up to the Internet has software called TCP/IP (Transmission Control rotocol/Internet Protocol) which is responsible for receiving, sending and checking information.  int 


The word LASER is an acronym for Light Amplification by Stimulated Emission of Radiation which describes the process by which lasers generate visible, ultraviolet or infrared emissions. A laser is a device that creates and amplifies a narrow, intense beam of coherent light. The light produced by a loser has very different properties to that produced by other sources (such as the sun, light bulbs and fluorescent or neon tubes). Laser light is monochromatic (a single wavelength) and typically confined to a narrow beam which spreads slightly with distance. Thus, the energy carried by a laser beam is concentrated in a small area and can travel efficiently over large distances. Lasers are widely used in industry for cutting and boring metals and other materials, in medicine for surgery, in communications, scientific research and holography. They are an integral part of such familiar devices as bar- code scanners used in supermarkets, scanners, laser printers, and compact disc players 


  MRI stands for Magnetic Resonance Imaging. MRI is a way of getting the pictures of the various parts of your body. To perform an MRI scon, the patient is securely placed on an imaging table within a large MRI scanner Powerful magnetic fields are administered to align the nuclei within the atoms of the patient’s body. Next, radio frequency pulses are applied; finally, the nuclei release some of the radio frequency energy and these emissions are detecied by the MRI equipment. With this dato, o computer generales o surprisingly detailed view of tissues within the body. The pictures of almost any part of your body can be obtained at almost any particular angle. In particular, the brain, the spinal cord and the nerves are seen much more clearly with MRI than with regular | x-rays and CAT scans. Also, muscles, ligaments and tendons are seen quite well. This method of scanning was developed primarily for use in medicine but it has also been used to study fossils and historical artefacts. 


 A kaleidoscope resembles a short telescope with a rotating end piece. When you look through a kaleidoscope, you will see a colourful, geometric patter. Twisting the end piece creates ever-changing, mesmerizing new patterns. A kaleidoscope consists of two or more mirrors laid lengthwise inside a tube. Coloured beads, liquid filled ampules or other small objects reside in the larger end of the tube. The viewer looks in one end and light enters the other end, reflecting off the mirrors. Typically, there are two rectangular lengthways mirrors, Setting of the mirrors at 45° creates eight duplicate images of the objects, six at 60° and four at 90°. As the tube is rotated, the tumbling of the coloured objects presents the viewer with varying colours and patterns. Any arbitrary pattern of objects shows up as a beautiful symmetric pattern because of the reflections in the mirrors. Some sources claim that the kaleido- scope was known to ancient Greece, but the Scottish inventor, David Brewster, is credited with its modern invention in 1816, 


 Asilicon chip is an electronic equipment consisting of a small crystalo a silicon semiconductor fabricated to carry out a number of electronic Functions in an integraled circuit. A silicon chip is usually less than one centimetre square and about half a millimetre thick. It contains millions of transistors (devices that control the flow of electric current) and other tiny electronic circuit components, packed and 1 grid of thin layers beneath the surface. There is metallic wires on the surface of the chip, which is used to make elednical connections to other devices. This tiny component is responsi- ble for arithmetic, logic, and memory functions in a computer. In addition to being used in com. puters, silicon chips are used in calculators, microwave ovens, automobile radios and engine controllers, and video cassette recorders (VCRs). The silicon chip was invented in 1961 by two American electrical engineers, Jack Kilby and Robert Noyce.


  A hovercraft is a vehicle that travels above the surface – land or water. A hovercraft has a powerful cushion of downwardly directed air powered by fans and trapped inside a flexible skirt, which greatly increases its lift capacity. A thrust propeller allows the craft to move forwards. The hovercraft was invented in 1952 by Sir Christopher Cockerell, who conducted a simple experiment to prove the principle that a vehicle suspended on a cushion of air would increase the mobility of the vehicle and allow it to traverse a wider variety of terrains. Modern hovercraft are used for many applications where people or equipment need to travel at speed over water. The hovercraft engine Orovides the power to drive large fans that blow air under the craft. The air is retained by a rubber ‘skirt’ that enables the craft to travel over a wide range of terrain. The skirt simply gives way when an obstacle is encoun- tered. The engine also supplies power to a thrust propeller of some kind that pushes the craft forwards on its ‘bubble of air. Rudders, like on an aeroplane, steer the direction of the craft. 


  quartz does not split easily. Glass can’t transmit ultraviolet light, but Quartz is a very hard substance – harder than a steel file. Also, most current passes throught it, it vibrates a little bit. When put under quartz con Quartz is piezoelectric meaning that when an electrical pressure, quartz con generale a small electric charge by itself. Quartz is commonly used in the industrial world for various purposes, such as for making special lenses, prisms and quartz-glass fubes for lamps. Quartz is also used in the manufac turing of the tubes, crucibles ond glass which are used in a laboratory. Quartz has diverse applications such as its use in an ordinary glass-manufacturing factory for making glass, as a material used in the construction business and in the foundry industry for making moulds. It is also used as a filter for some liquids, in the manufacturing of sandpaper and whetstones, in the scouring of powders, in sandblasting. Quartz digital watches are known the world over for their precision. 


  Blast furnaces are usually tall shaft-type steel vessels, up to ten storeys high, internally lined with refractory brick and superimposed over a crucible-like hearth. The purpose of a blast furnace is to reduce chemically and convert iron oxides physically into liquid iron called hot metal or pig iron. The necessary charge to produce molten pig iron consists of iron-bearing materials, coke and flux. The charge is introduced into the furnace at the top. Blasts of heated air from large blast stoves, and in most cases gaseous, liquid, or powdered fuel, are injected into the furnace through openings at the bottom of the shaft just above the hearth crucible. As the hot air encounters the coke, the coke is burned along with the injected fuels, producing the necessary heat and reducing gas to remove oxygen from the ore in the reduction process. As the iron melts, it descends and accumulates in the crucible. The molten pig iron and slag are drained from the crucible through different tapping holes. The gas that exits from the top of the furnace goes through a cleaning process.  


  LPG is Liquefied Petroleum Gas. Liquefied Petroleum Gases (LPG) obtained by the refining of crude oil and from natural gas by on of hydrocarbons, which are gaseous at normal ambient temperature absorption or refrigerated absorption process. LP Gases are mixtures and atmospheric pressure, but can be liquefied at normal ambieni temperature by the application of moderate pressure. LPG is stored drawn out and used as o LP GAS heavy as air transported in containers as a liquid, but is generally gas. LPG in gaseous state is nearly twice as Liquid LPG is almost half os heavy as water. When liquid LPG gets converted to o gaseous state, ii expands by about 250 times. LPG can be used for various applications such as (a) Household – Cooking/Heating/ Lighting (b) Agriculture – Grain drying / Weed killing / Preservation of fruits / tobacco curing / Tea drying (c) Automobile Heat treatment / Paint baking (d) Ceramics Biscuit & Glost firing of porcelain & stoneware (e) Chemicals & Drugs – Heating & Drying (1) Electrical – Bulbs & Tubelights manufacture / SOK filament manufacture/Battery.  


 A sundial is essentially a clock. But more specifically , it is a clock that uses the position of the sun to indicate the time. A sundial is the most the ground, which casts a primitive form of a clock. The simplest sundial consists of a stick set in shadow indicating the time of day. No one can be sure when the first sundial appeared. But we do know that as early as 3500 B.C., the Egyptians were building sundials that not only kept time but also indicated the longest and shortest day of the year. We have days and nights on the Earth as the Earth rotates around its axis. Approximately, every 23.6 hours, our Earth makes one complete rotation and as we rotate, we rotate away from the sun (night) and back towards it (day). A sundial works by gauging the sun’s position in the sky relative to where we are in that 24-hour period. The sun casts shadows on the sundial in different places as it moves across our sky, indicating different times. The time piece on the sundial is called a “gnomon”. By reading where the shadow falls when the sun hits the gnomon, we can estimate the time of 


 A bullet is a solid projectile propelled by a firearm or air gun and normally made from metal (usually lead). A rocket is a vehicle, missile is or aircraft which obtains thrust by the reaction to the ejection of fast moving fluid from within a rocket engine Rockets go about 25 times faster than the fastest bullets. If a bullet went as fast as a rocket, it would escape the Earth’s gravity and keep going perhaps to Mars. Indeed, the Earth’s escape velocity (ignoring air friction) is almost 10 times the fastest bullet 25,000 mph (40,320 km/h). In 2001, the spacecraft Odyssey left the Earth for Mars at about 67,100 mph (1,08,000 km/h) and cruised thereafter at about 54,000 mph (87,000 km/h). The fastest bullet (probably the Winchester 223 Super Short Magnum) has a muzzle velocity of about 4,000 feet per second or 2,700 mph (4,400 km/h). 


 Germs are tiny organisms or living things that can cause disease. Germs are so small and sneaky that they creep into our bodies without being noticed. In fact, germs are so tiny that you need to use o microscope to see them. Once germs have invaded our bodies, they snuggle in for a long stay. They gobble up nutrients and energy, and can produce toxins, which are like poisons. Those toxins can cause the symptoms of common infec- tions, like fevers, sniffles, rashes, coughing, vomiting, and diarrhoea. Germs spread through the air when someone coughs or sneezes. Germs can also appear in bodily fluids like saliva, sweat and blood. The best way to avoid getting germs is to stay away from these areas where germs spread. There are many different kinds of germs, but the four most common are: bacteria, viruses, fungi and protozoa. Each of these types of germs causes different symptoms or illnesses. For instance, while bacteria germs cause minor illnesses such as ear infections, sore throats and cavities, viruses cause more serious diseases such as chicken pox, measles and the flu.  


 A compass is an extremely simple device. A magnetic compose consists of a small, lightweight magnet balanced on a nearly nicionless pivot point. The magnet is generally called a needle. One end of the needle is ofter marked “N’ for north. The magnetic compass is an old Chinese invention, probably first made in China during the Qin dynasty (221-206 B.C.). is the oldest instrument to navigation and has been a vita fool for navigators at sea for centuries. The compass allows a ship to steer a selected course. A magnetic composs works because the Earth is like a giant magnet, surrounded by a huge magnetic field. The Eart has two magnetic poles which lie near the North and South poles. Th magnetic field of the Earth causes a magnetized ‘needle of iron or stea to swing into a north-south position if it is hung from a thread or if it stuck through a strow or piece of wood floating in a bowl of wate Needles were magnetized by strokin them with lodestones, lumps magnetic rocks called magnetites E S 


 Dynamite is one example of a chemical explosive. An explosive is ignited, burns very rapidly and produces a large famount of hol gas in the process. The hol gas expands very quickly and applies pressure. A Swedish industrialist, engineer and inventor, anything that, once  Alfred Nobel, built bridges and buildings Stockholm. His construction work inspired Nobel to research new methods of blasting rocks. In 1860, Alfred first started experimenting with nitrogly- cerine. Nitroglycerine was first invented by an Italian chemist, ceny ne w01 Ascanio Sobrero, in 1846. In its natural liquid state, nitroglycerine is very volatile. Alfred Nobel understood this. In 1866, he discovered that mixing nitroglycerine with silica would turn the liquid into a malleable paste, called dynamite, One advantage of dynamite over nitroglycerine was that it could be cylinder-shaped for insertion into the drilling holes used for mining 


 Quicksand is not a unique type of soil, it is usually just sand or another type of grainy soil. Quicksand is nothing more than a soupy mixture of sand and water. Quicksand is just ordinary sand, but it can cause one to sink because it becomes oversaturated with water and the friction beňween sand particles is reduced. The resulting sand is a mushy mixture of sand and water that can no longer support any weight. Sand slips apart rapidly when weight is put onto it, as a person stepping on it might do. Hence, the term quicksand applies to sand that quickly allows one to sink into it. People tend to be drowned in quicksand it they fail their arms and legs about. This makes them sink because they are literally helping the as quicksand split apart. On the other hand, the person who does not panic and who puts one’s hands and legs slightly apart, moving as slowly possible, will not sink under the quicksand.   



Science and technology


mes meaning small and skopos meaning watcher. A The microscope comes from two Greek words to smo for the numon eye to see. There are two roscope is a device used to look at things that ore poes of microscopes – optical and electron. An conical microscope uses lenses to mognity the coge up to 200 times. An objective lens bends light roys apar to enlarge whoi you see. An electron microscope is much better because it magnifies an moges a million times. We know at light travels in the form of waves. Noves are also associated with noving electrons. These are called natter waves. An electron hicroscope makes use of matter aves associated with electrons. A beam of electrons is concentrated onto the object. With the help of electromagnetic lenses, a magnified image of the object is made on a fluorescent screen. This image is photographed on a photographic plate and the object structure is studied in detail.


  Every action has an equal and opposite reaction – this principle was introduced by Newton, and is popularly known as Newton’s third law of motion. A jet engine works on this principle. Its working can be compared to the action of a swimmer, who swims forwards by pushing water IONIAM backwards. According to Newton’s law, the action is pushing the water backwards and the opposite reaction is the forward movement of the swimmer. Similarly, o jet engine ejects (pushes backwards) gases at the rear with a great speed and the resulting opposite action is the moving of the aircraft in the forward direction at an equal speed. Ajet engine has fuel inside it which, when burnt in the engine, generates a great amount of hot gases. These hot gases explode out at the back with a great force and the engine reacts by being pushed forwards with an equal force. 


  odern times. Basically, a camera is a dark box 1 camera is the most vital mode of communication in which has a lens on one side. Just behind the lens, there is an aperture which manages the amount of light coming in. A shutter exposes the SONY Cuberhot film to the light for a short period. A photosensitive film is mounted on the other side of the lens. This film has a coating of silver bromide. The object whose photograph is to be clicked is focused on the film. This is done with the aid of another lens known as o view finder. On opening the shutter, the light from the object enters the box through the lens. An inverted image of the object is taken on the photo film. The exposed film is taken out of the camera and developed. For developing the film, a solution of quinol and metal is used. En


 Most of the paper is made from woodpuf Wood logs from trees like pine excalais birch for and Chestnut are token toe paper mill where the bark is Stripped off them. They are, then cut into chips. These chips are put into huge vals containers) where they are boiled and stirred with chemicals until they become a suggy pulp. This is washed thoroughly and bleached to make white paper. pu Adhesives such as glue are added to make the fibres link together in phe poper. The pulp is, then, combined with china clay or chalk to improve the capacity and surface finish of the paper. After this, it is spread out on a belt of wire sieve of a refining machine. The water drains out through the holes in the sieve and fibres begin to stick together into a thin sheet. This sheet ,then, passes through a number of felt covered rollers that squeeze out the remaining water. Finally, it goes through polished iron rollers which make its surface highly smooth. 


 Atoms are tiny bits or particles which get together to make each and every substance. An atom is the tiniest bit of any chemical element. The centre of an atom is made up of two kinds of particles-protons and neutrons. Around the nucleus, tiny particles called electrons move about. Electrons are particles that have a small negative charge of electricity. Protons are about 1,836 times as heavy as electrons and have a positive charge of electricity. The neutron, which is still heavier, has no charge at all. Atoms have negligible weight. A single atom of hydrogen weighs around a million-million-million- millionth of a gram. Do many atoms there would be in a single gram of hydrogen. The answer is 6 followed by 23 zeros. you know how


 Food grown in one part of the world may be transported for use in distant places. Hence, it requires processing for longer storage. If food is  not processed, it may be spoiled by bacteria and moulds present in the our In a canning factory, the food is prepared in large containers It is brought to boil in order to destroy micro- organisms and to bar enzyme activity. The germ-killing temperatures vary from 1000 C to 1210 C. The containers are sterilized according to the types of food items. After being heated, the food goes to the conning machine, which is kept with a line of empty cans. The food is filled in the metal or glass containers with a liquid such as sucrose syrup. Air is eliminated from the containers. Then, they are sealed with wairtight lids. Most canned food items SCIE can be preserved for more than a year.


  Plastics are synthetic, man-made materials that can be easily shaped or moulded. Most plastics are polymers, i.e. substances with long chains of organic molecules made up from lots of smaller, identical molecules. The structure of polymer molecules is what gives different plastics their properties. The long chains of molecules that slide over one another easily make flexible plastics like polythene. Tangled chains make rigid plastics such as melamine. The first synthetic plastic was made from the plant material cellulose, In 1869, John Wesley Hyatt, an American printer and inventor, found that cellulose nitrate could be mixed with camphor. Hence, this new material had become the only plastic of commercial importance for 30 years Then in 1951, two young research chemists made more discoveries the revolutionized the plastic world. Bakelite


 Glass is one of the most versatile of all materials. It is transparent, easily moulded and resistant to weather. It is made from ordinary sand (made of silica), soda ash (sodium carbonate) and limestone (calcium carbo. nate). Glass can be made from silica only. As silica has a very high melting point (1,700°C), soda ash is added to lower its melting point. But soda ash cannot be added in large quantities since it will make glass too soluble in water. Therefore, limestone is added to decrease its solubility. In order to make glass sheets, 6% lime and 4% magnesia (magnesium oxide) are added to the basic mix. The mix is heated in a furnace. Then, the liquid glass is dropped into a mould. The liquid spreads into the mould. Compressed air forces the liquid into the shape of the mould. This is how various things like bottles and glasses are made.


  A battery is a device that generates electricity by chemical action. A battery consists of carbon and zincos electrodes. A nail-like collector is inserted from the bottom. The granules of zinc which constitute the anode are made equal in size and shape. The electrolyte, which is o solution of potassium hydroxide, is in direct touch with the anode, ensuring that the anode is completely used up throughout the entire life of the battery. The manganese dioxide cathode is obtained by electrolysis. The substances in the battery react chemically with one another to produce an electric current. As a result of chemical activity, a positive charge builds up at one electrode. This flows through a conductor such as a wire to the other (negative) electrode.


  Light is generated when electricity is passed through wires. To stari with, Edison used a coil of very platinum wire and sealed it in a glass bulb. When the two fine ends of this coil became red hot, it began to glow. The lamps manufactured by Edison could not become famous because platinum wires were very expensive. Later on, filaments comprising fungsten came into being. Since the melting points of these metals are very high, filaments made from them did not easily melt. An electric bulb is a sealed glass bulb with a coiled tungsten filament. Each end of the filament is attached to a thick wire. The two ends ore soldered with contact pads. The air inside the glass bulb is eliminated and filled with a combination of argon and nitrogen gases. When an electric current is passed through the filament, light is produced.


  Laser light is a bright artificial light. A laser is very thin, but very powerful ray of light. It is so powerful that it can drill a hole through the hardest substance, ie. diamond, Losers amplify light by causing photons to be bounced back and forth, until they all are travelling together. Inside the laser, there is a tube filled with gases such as helium or neon or a liquid or solid crystal such as ruby. Laser beams are highly monochromatic and coherent, which means that the light waves are all of the same wavelength. Also, they are perfectly in a series like a well- ordered army platoon. Lasers are widely being used in communications computers, the welding and drilling of metals, photography, stone remove from the kidneys without an operation, heart surgery, meteorology etc.


  An anticial sotellite is a man-made moon that revolves around the Earth. With the aid of rockets, artificial satellites are launched into geostationary orbits. These geostationary orbits have solar cells which transform the energy of IAANIKA the Sun into electricity which is employed to run the artificial satellites. Commu- nication satellites pick up signals transmitted from a particular point on the Earth and relay them to the other side of the world by amplifying them and then beaming them down to the ground station. A communication satellite possesses different channels for telephone, radio and television signals. The signal is first sent to the satellite with the help of high frequency microwaves. This is received by the antenna fitted in the satellite. After amplifying the signal, it is transmitted by a transmitter. Finally, the signal is received by the earth station. In this manner, a signal covers thousands of kilometres


  A computer is on equipment for processing information very rapidly and accurately. A computer is a digital system in which every piece of information is stored in the form of a bit . A bit is a variable that can have only two variables 0 and 1. The computer is divided into three main parts-memory input/output and CPU (Central Processing Unit). Memory has the function of remembering the value of bits. Hard disks and RAM are the two kinds of memories. The input/output system takes information from the outside world and sends them either to the memory or the CPU. The keyboard and the screen are parts of this system. The CPU is the heart of the computer. It does all the interpretation and manipulation of bits. The CPU is implemented by a microprocessor which takes in the bits of instruction telling the microprocessor what it is supposed to do. The motherboard is a circuit board whose main function is to hold the CPU and the connections between the CPU and all the other systems.


 Things Wool because they are less dense than water. When on oben immersed in water its weight pushes in down. Al the same limo, the water pushes it back with a force equal to the weight of woter Hisplaced. The upward push on o floating object is kolled buoyancy Objects which are penser than water sink when the weight of the object is not equal to the upward push of water. The water offsets the force of gravity which tries to pull everything to the centre of the Earth. This is how boats float, Steel ships float on the same principle. Although steel is denser than woler yet the hell of a steel ship is full of air. The ship floats till enough water is displaced to match the weight of steel and oir in the hull,


Nuclear energy is produced by releasing energy from the nuclei of millions of atoms. The energy thai binds the nuclei of atoms together is enormous. Nuclear energy is produced in two ways. When nuclear energy is released by fusing together small atoms like deuterium (an isotope of hydrogen), it is called nuclear fusion. When energy is released by splitting the nuclei of large atoms like uranium and plutonium, it is called nuclear fission Nuclear fission involves firing a neutron into the nucleus of a uranium or plutonium atom. As neutrons crash into atoms and split their nuclei, they split oft more neutrons. These neutrons bombard other nuclei, splitting off more neutrons that bombard more nuclei. This is called a chain reaction Once this chain reaction is started, it continues and releases very larg quantities of energy uon


  gos. These are called states of matter. Substances change their states There are three states in which a substance can exist – solid, liquid and at particular temperatures and pressures. A solid melts into a when the temperature rises. As the temperature further rises, the liquid evaporates to become gas. Melting point is the temperature at whicha solid melts and boiling point is the temperature when a liquid turns into gas. Every solid has a definite shape as its molecules are firmly bonded in a ngid structure. Ice melts to water because heat makes its molecules vibrate faster and faster, until the bonds between them eventually break. A liquid flows because the bonds which hold the molecules together are loose enough to move Over one another 


 A microphone is a device which transforms sound waves into electrical signals. These signals can, then, be broadcast through the air or sent over to far-off points where they can again be transformed back into sound. Microphones can be classified into two groups, depending upon how they react to sound waves. They are pressure type and velocity type. The pressure type microphone has a thin metal plate known as diaphragm. This is stretched like a drumhead inside a rigid frame. The diaphragm is a portion of the electrical circuit. When sound waves hit the diaphragm, it begins to vibrate at the rate as the sound waves. These vibrations make corresponding electric signals by converting the electric current that flows through the circuit. In the velocity type microphone, the vibration varies with the capacitance of the condenser. Same


  A detergent is an organic substance, composed of the compounds carbon, oxygen, sulphur and hydrogen. All soaps and deterger contain a vital cleaning agent called surfactant or surface acti- acent. The molecules of a surfactant attach themselves to the particle of dirt on dirty surfaces and lift them away. A surfactant works becaus its one part is hydrophilic (attached to water) while the other hydrophobic (repelled by water). The hydrophobic tail of a surfactar digs its way into the dirt, while the other tail is drawn into the water. The surfactant increases the wetting ability of water by reducing its surface tension. The surface tension is the force that keeps water molecules separate from one another and helps to move deeper into the soiled material. This is how dirt particles are removed.  

Science and technology


Plastics are synthetic materials that can be easily shaped and moulded. The long chains of molecules that slide over one another easily make flexible plastics like polythene, whereas rigid plastics like melamine are made from tangled chains. All plastics that are made SE belong to one of the two basic types. They are based on how they behave when heated. The two types of plastics are thermoset plastics and thermoplastics. Thermoset plastics are those which cannot be remelted once set. They are used to make telephones and pan handles. Thermoplastics are soft and can easily be moulded when warm. When cooled, they become solid. They can be melted and reformed again and again. They are used to make bottles and drain pipes. Polytetrafluoroethylene is a thermoplastic which resists heat. It is mainly used for frying pan coatings, valve seats, gaskets, bearings and cable insulation. 


Aluminium makes up about 8% of the Earth’s crust and is also the most common metal on the Earth’s surface. Aluminium is not found in its pure form in the ground. It is extracted from the layer of a soft ore called bauxite which is mostly aluminium hydroxide. Aluminium was first made by Hans Oersted, o Danish scientist, in 1825. About 5,000 years ago, people used alum powders made from aluminium compound for dyeing. Aluminium is one of the lightest of all metals. When freshly Imade, it is silver in colour. When it comes in contact with the air, it becomes white. Aluminium boils at 2,450 degrees Centigrade and melts at 650 degrees Centigrade. Corumdum is one of the hardest minerals and is made by crystallizing aluminium oxide. It is used in sharpening knives. Every year, 21 million tonnes of aluminium is made mostly from bauxite dug up in Brazil and New Guinea 


A gear is a mechanical device that transfers rotating motion and powers from one port of a machine to another Gears are set of wheels of different sizes that turn together. They make it easier to cycle uphill or accelerate a car from a standstill. Gears are produced in a wide range of sizes and vary greatly in use. Tiny gears drive the hands of a watch, whereas huge gears for the propeller of a supertanker. Interlocking geor wheels are used in a huge range of machines from cors to cameras The wheels transit movements as well as control their speed. A simple gear consists of a metal wheel or disc with slots called teeth around the edge. The teeth of one gear fit together with the teeth of the other gear Each gear has a metal ade in the middle. The axle of one gears connected to an electric motor. When the power axle turns, its gear tums and causes the second gear to rotate in the opposite direction.  


Helium is recovered from natural gos deposits where it accumulates over millions of years as a product of radiocative decay Some natural gos depois have as much as 7% helium Such deposits have been found in Texas, Russia, Poland, Algeria, China and Canada. Helium extracted from these natural gas reserves is the single source of helium Helium is called a noble gas because it does not regularly mix with other chemicals and form new compounds. It has the lowesi boiling point of all the elements. It is the second most common element in the universe ofter hydrogen. It has neither colour nor smell. Helium wos first detected in the year 1868 by o French astronomer Pierre Janssen who termed it as an unidentified yellow spectral line-signature. It was later on recognized as an altogether new element by a British astronomer Norman Lockyer. Helium is used to fill balloons and airships because it is lighter than air. It does not burn or react. It is also used in some kinds of light bulbs  


A transistor is an electronic Switch that controls the flow of electric current. A transistor is made of a solid piece called a semi- conductor material, with, at least three terminals for connection to an external circuit. The transistor was invented in December 1947 at Bell Labs by John Bordeen, Walter Brattain, and William Shockley. It is found in radios, television sets, computers and almost every End of electronic equipment. Semi-conductors in transistors change their ability to condud electricity Electronic systems work by Initing monytanssiors together so thai each may control the way the othes work. Transistors are smaller, lighter, cheaper to operate, less expensive and more reliable than vacuum tubes which were used earlier instead of fransistors Transistors are the main components built into computer chips. Some chips no longer than fingemoils contain millions of mansistors. A transistor hos two basic functions 1. to switch an electric current on or OF, and 2. to amplity or strengthen on electric  


A transistor is an electronic Switch that controls the flow of electric current. A transistor is made of a solid piece called a semi- conductor material, with, at least three terminals for connection to an external circuit. The transistor was invented in December 1947 at Bell Labs by John Bordeen, Walter Brattain, and William Shockley. It is found in radios, television sets, computers and almost every End of electronic equipment. Semi-conductors in transistors change their ability to condud electricity Electronic systems work by Initing monytanssiors together so thai each may control the way the othes work. Transistors are smaller, lighter, cheaper to operate, less expensive and more reliable than vacuum tubes which were used earlier instead of fransistors Transistors are the main components built into computer chips. Some chips no longer than fingemoils contain millions of mansistors. A transistor hos two basic functions 1. to switch an electric current on or OF, and 2. to amplity or strengthen on electric  


Oils are liquids that do not dissolve in water and burn easily. They are usually made from the chains of carbon and hydrogen atoms. There are three main kinds of oils – essential, fixed and mineral oils. Essential oils are thin, perfumed oils from plants. Essential oils often have an odour and are, therefore, used in food flavouring and perfumery. Essential oils are usually prepared by fragrance extraction techniques such as distillation (including steam distillation), cold pressing or extraction. Fixed oils are made by plants and animals from fatty acids. They are non-volatile oils specially found in fatty animal tissues and the seeds of various plants, including cotton, corn, flax, sunflowers, peanuts, coconuts and olives. Mineral oils come from petroleum formed underground over millions of years from the remains of sea organisms Mineral oils are of the most inexpensive by-products that are made from petroleum. Mineral oils are transparent and colourless. They are composed of a blend of hydrocarbons. iver 5 of 28


Asteroids are pieces of rock and metal that travel round the Sun. They are sometimes considered as minor planets. Astronomers are not sure how they originated. However, they are thought to be lett-over material from the formation of the solar system. Most asteroids orbit in the Asteroid Belt which lies between Mars and Jupiter some asteroids come near the Earth. These are called Near Earth Objects (NEOs). Asteroid 433 Eras is a NEO Ceres was the first asteroid discovered in 1801. It was detected by Giuseppi Piazzi. It is also the biggest asteroid with a diameter of 940 km and is 0.0002% the size of the Earth. A few asteroids like the Ida have their own moons. Ida has its own miniature moon called Dactyl. The third biggest asteroid Vista is the only member of the belt close enough and large enough to be seen with the naked eye. Although asteroids orbi’ close to the Earth, it is believed that they strike the Earth once every 250,000 years. 


Scientists are of the view that life could exist on Earth- like plonets. They also believe now that life may be able to start in many places where there is water. One of the most likely places in the Solar System where life con exist is Jupiter’s moon Europo. Europa is one of the smoothest bodies in the Solar System. Europa has a mostly flat surface, with nothing exceeding 1 km in height. The surface of Europa is also very bright, about 5 times brighter than our Moon. Its surface is made of ice. Scientists believe there may be a huge ocean of liquid water underneath the frozen surface. The water remains in liquid form by the heat generated by the gravitational stress due to Europa’s close orbit to Jupiter. Such an ocean could provide a home for living things. The surface layer of ice is 80- 160 km deep. It also has very thin atmosphere. Its surface-features include shallow cracks, valleys, ridges, pits and blisters which do not extend more than a few hundred yards upwards or downwards. 


Observatories are special places where astronomers study space. Most observatories are built on mountain tops far from city lights. They are built at high altitudes so that smoke, light and pollution may not interfere with the view. Telescopes are placed in a dome- shaped roof of the observatory which turns around so that they may keep aiming at the same stars while the Earth rotates. Devices called interferometers are used to link telescopes together to build a computer controlled and more detailed image of a subject. The first photographs of the stars were taken in 1840. Observatory photographs are made using sensors called Charge- Coupled Devices which give off electrical signals when struck by light. London’s Royal Greenwich Obser- vatory, founded in 1675, is one of the oldest working observatories. An observatory in Beijing, China, has 500-year-old bronze asironomical instruments. The highest observatory on the Earth is in Denver, Colorado, USA. It is 4,300m above the sea level.  


Radio telescopes are like olant satellite dishes that Dickupinasible radio waves, instead of lightwaves. Unlike optical telescopes, radio Telescopes can operate 24 hours a day and through thick cloud and air pollution Most radio telescopes use concave or bowl shaped dishes to collect radio waves from space. From the dishes, the waves are reflected to antennae which send the signals to amplifiers in the receivers where the signals are amplified. Then, computers are used to process the signals into images and data. The first radio telescope was built by on American, Grote Reber, in the 1930s. In order to get super occurate results, many small dishes are linked together to form an array. The world’s biggest single dish radio telescope is the Arecibo dish in Puerto Rico in the Carribean. It was built 40 years ago and is 300 metres across 


Most stars are formed within a huge cloud of gas and dusi called a nebulo. There are milions of nebuloe in space which can be seen from the Eorth when they reflect light from nearby stors. The forces within the nebula pull-off the gravity of the gas or a shockwave coused by a nearby stor explosion make the cloud of gas and dus shrink and grow hotter. As this happens, the nebula breaks up int smoller clumps, each of which may eventually form a star. Slowly, th knot of matter gathers together in a disc. As the disc spins, it heats 4 until o nuclear reaction takes place and a new star is born. Stars a being born and dying all over the Universe. Big stars have short lives of 10 million years. Medium-sized stars last for about 10 billion years, whereas small stars may lost for 200 billion years. Siars are fuelled by the nuclear fusion of hydrogen to form helium deep in their interiors. The outflow of energy from the central regions of the star provides the pressure necessary to keep the stor from collapsing under its own weight. It also provides the energy by which it shines. 


Sunspols are dark spots on the surface of the Sun which are 2,000 degrees Centigrade cooler than the rest of the surface. The coolest bit of the sunspot is the dark centre called the umbra. There is the penumbra around it. Some sunspots appear as mere specks on the Sun’s surface. They also appear in groups which can be som times the size of the Earth. Sometimes they measure 2,00,000 miles in length. These groups seem to move across the Sun over two weeks as the Sun rotates. The number of sunspots reaches a maximum every 11 years. This is called the solar or sunspot cycle. When sunspots are at their maximum, the Earth’s weather may become warmer and stormer. The observations of the Sun by satellites like the Nimbus 7 showed that less heat reaches the Earth from the Sun when sunspots are at a maximum. 


Nuclear power is any nuclear technology desi- gned to extract usable energy from atomic nuclei via controlled nuclear reactions. The most common method today is through nuclear fission, though other methods to include nuclear fusion and radioactive decay. All utility-scale reactors heat water to produce steam, which is, then, converted into mechanical work for the purpose of generating electricity or propulsion. The steam is used to turn turbines connected to electricity generators. Calder Hall nuclear power station in England was the world’s first nuclear power station to produce electricity in commercial quantities. It was opened in 1956 by Queen Elizabeth with an initial copacity of 50 MW. Today, more than 15% of the world’s electricity comes from nuclear power. More than 150 nuclear-powered naval vessels have been built. A few radioisotope rockets have been produced. 


A windmill is a machine that converts wind into useful energy. This energy is derived from the force of wind acting on oblique blades or sails that radiate from a shalt. The turning shaft may be connected to machinery used to perform such work as milling grain, pumping water or gener bating electricity When the Shott is connected to a lood, such as a pump, the device is typically called a windmill. The first windmills were developed by the ancient Persians (now Iran) as early as 600 AD. They were used for irrigation and milling grain. The wheel bearing the wind sails of the earliest windmills was horizontal and supported by a vertical shaft. These machines were relatively inefficient. Nevertheless, these types of windmills spread to China and throughout the Middle East. But the earliest windmills in Europe first appeared in France and England around 1100 AD. These early wood structures, called post mills, were rotated by hand around o central post to bring the sails into the wind. 


Saudi Arabia hos the largest petroleum reserves in the world. It comprises almost 1/4th of the world’s proven total petroleum reserves Saudi Arabia’s economy is petroleum-based; roughly 75% of budget revenues and 90% of export earings come from the oil industry. Officially, it has about 260 billion barrels(41,000,000,000 cubic metres) of oil reserves It has become one of the rapidly growing countries in terms of the average per capita income. Although Saudi Arabia has around 100 major oil and gas fields yet over hall of its oil reserves are contained in only eight giant oil fields including the Ghawar Field, the biggest oil field in the world with ar estimated 70 billion barrels of remaining reserves. Saudi Arabia maintains the world’s largest crude oil production capacity, estimated to be around 11 million barrels per day at mid-year 2008 and has announced plans to increase this capacity to 12.5 million barrels per day 


Originally, vanilla came from Mexico, Central America and the Caribbean. It was a fruit of America. Now, it grows in tropical countries all over the world. We get vanilla from the vanilla orchid, which grows in Madagascar and other islands in the Indian Ocean. The vanilla orchid is the only orchid which produces a useful product, Vanilla is the most labour- intensive agricultural product in the world. It takes between 18 months to three years from planting a cutting of the orchid vine till the plani produces orchids. The orchids bloom and die within a few hours unless they are pollinated by hand. The beans (which are actually seed-pods) must stay on the vine for nine months before being harvested. The beans, then, go through a curing, drying and resting process for several months. Each vanilla bean is handled over o hundred times before it’s ready to use. Vanilla has over 250 organic components that comprise its distinctive flavour and fragrance Madagascar is the largest producer of vanilla worldwide, followed by Indonesia. Reunion and the Comoro Islands were, until recently, big producers as well.


The moment you put a match to the wick, you starte change in the candle by turning the solid wax inte a liquid The liquid wax rises to the wick by an irresistible process called capillarity. Then, the liquid wox changes into a gas which burns a chemical reaction is chemical reaction releases energy in the form of light and heal. The presence of the gas can be demonstrated by blowing out the candle and immediately holding a lighted match an inch or so above the wick. The inflammable vapour instantly colches fire and the candle Wahts up again without the match having actually touched the wick, Other changes take place while the candle bums. The wax is a complex chemical compound of carbon and hydrogen. The process of buming is simply the combination of the wax with the oxygen in the air. If you put a jar over the candle, it will quickly use up the oxygen and go out During the time the candle burns, the carbon joins with the oxygen in the air and makes carbon monoxide and carbon dioxide. The hydrogen combines with the oxygen to produce water. While all these changes in the substance of the candle take place, the candle, of course, becomes shorter Ils materials simply change into other substances   


All living things are based on carbon. It is one of the most important chemical elements. Still, it makes up only 0.032% of the Earth’s crust. Carbon is the main component of fuels like coal, petroleum and natural gas. It is also found in many plastics. Pure carbon occurs in four forms diamond, graphite, amorphous carbon and fullerenes. All the four forms have different crystalline structures which means that their atoms are differently arranged. Diamond is The world’s hardest natural substance. The extraordinary hardness of diamond is due to the fact that the carbon atoms forma pyramid shape. Graphite is soft black carbon used in pencils. It is soft because it is made from the sheets of atoms that slide over one another Amorphous carbon is the black soot which is left after candles and other objects have been burned. Fullerenes are big molecules made up of 60 or more carbon atoms linked together in a tight cylinder or ball. Carbon does not react chemically at room temperature. Neither diamond nor graphite melts at normal pressures.