My Science School

             A car engine will stall-that is to say, it will suddenly stop when you do not want it to - if it is unable to provide sufficient power to overcome the load on the back wheels.

            This power is provided by the explosion of the petrol and air mixture pushing down on the pistons. If the load on the pistons from the crankshaft is exerting a greater force than that created by the explosion, the pistons will not move down the cylinder and the engine will stop. This can happen if the clutch is engaged too rapidly or if the hand brake is left on.

           Fire is the outward sign that oxygen is combining with other substances in a spectacular chemical reaction. As the air is rich in oxygen, many materials will burn freely in a process scientifically called combustion, if their temperature is raised high enough. This explanation of what had been considered a mysterious phenomenon was discovered by the French chemist Antoine Lavoisier in 1783.

            The discovery of fire may have changed early man’s wandering mode of life to a more settled one because of an urge to keep the fire burning. It provided him with a new weapon for survival, warmed his cave and huts, enabled him to cook, and helped to scare off dangerous animals.

             In ancient time’s people in Persia, Egypt and India believed fire to be representative of the sun.

               It is the built-in-skew or twist in a boomerang combined with its spinning motion that makes it return to the thrower. At first people believe that air, pressing on the lower flat surface and passing over the upper rounded face, was responsible for the return flight. But T.L. Mitchell, a Scottish explorer of Australia, gave the true explanation early in the 19th Century.

              The curved throwing stick is used chiefly by the aborigines of Australia for hunting and warfare. (They also use a non-returning kind of boomerang.)

              The boomerang is held at one end above and behind the thrower’s shoulder, with the concave edge of the front and swung forward rapidly with the flat side underneath. Just before it is released, it is given extra power with a strong wrist movement.

              If thrown downward or parallel to the found it sweeps upward to a height f 50 feet or more. When thrown so that one end strikes the found. It ricochets into the air at terrific speed, spinning endwise. It completes a circle 50 yards or more wide and then several smaller ones, up to five, before it drops to the ground near the thrower.

             Heating appliances specially designed to create a circulating movement of warmed air are called convection   heaters because they operate by using convection currents of air.

             When air is heated it becomes less dense and, therefore, duty rises and is replaced by cold air.

            Convector heaters consist, basically, of metal cabinets with openings at the top and bottom to produce and direct this flow of rising warm air. At the base of this cabinet there is a heating element and this warms the air within the cabinet.

            This warm air rises and, as it rises and, as it rises cold air is drawn into the convector from the bottom of the appliance. The cabinet of the convector acts as a flue or chimney and creates a continuous current of warm air.

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Bats use high-pitched sounds to find their way about. They are nocturnal animals. That is they move about by night. So they have developed their hearing to such an extent that they can find their way by a method known as echolocation.

     The blind-flying abilities of bats were first studied by LazzaroSpallanzani (1729-1799). He surgically removed the eyeballs from several bats to prove that they did not need to see to fly.

    In the 20th century, biologists, using electronic instruments, have carried out experiments with bats. They have discovered that bats find out where to go by emitting high-frequency sounds and receiving the echoes as they bounce off objects. Most of the sounds have too high a frequency to be heard by the human ear.

    Bats commonly fly together in groups, but apparently they are not confused by he sounds and echoes produced by each other. When hunting in woods and in the rain they are able to discriminate between the faint echoes bouncing off the ground, tree-trunks, branches, twigs and raindrops.

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The fist practical thermometer or instrument for measuring temperature was invented shortly before the end of the 16th century by the famous Italian astronomer Galileo. It was an air thermometer giving only a rough indication of the degrees of heat and cold, and later he increased its efficiency by using alcohol instead of air.

       The principle on which most thermometer work is that a liquid or gas used for measuring expands or contracts with changes in temperature more rapidly than the glass containing it. Thus when a coloured liquid is confined in a thin glass tube the difference in expansion, as shown by the level of the liquid against a graduated scale, indicates the temperature.

    About 1714 the German scientists Gabriel Daniel Fahrenheit designed a thermometer which, for the first time, used mercury as the measuring agent. He also introduced the scale named after him in which 320 is the freezing point of water and 2120 the boiling point. Mercury is still used in most thermometers because it has a high boiling point (6740) and a low freezing point (-380).

    An alcohol thermometer, still in use in some countries, was made by Rene de Reaumur, a French naturalist, about 1731. About 11 years later Andres Celsius, a Swedish astronomer, used the centigrade scale for the first time, with freezing point 00 and boiling point at 1000.

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X-Rays are electromagnetic rays of very short wavelength which can penetrate matter through which light rays cannot pass. We call this opaque matter. An X-ray photograph shows a picture of the internal structure of the body allowing doctors to diagnose broken bones and examine the organs of the body. In order to show the position and shape of the stomach and intestine harmless liquid containing barium is swallowed, and other opaque substances may be injected to show the outlines of other organ. Oxygen can also be injected into the brain to make its outline sharper.

        The discovery of X-rays was recorded in January 1896 by Professor Rontgen, Professor Physics at Wurzburg. Chest X-rays led to the early diagnosis of pulmonary tuberculosis and from these beginnings the science of radiography and radiotherapy developed until now countless X-rays installations are in daily use throughout the world. X-rays are used both to diagnosis and to treat deep-seated diseases like cancer. Scientific laboratories use them in experiments while industry uses them in work of investigation. By using high-tension apparatus giving up to 300,000 volts, steel can be examines for faults and hidden weakness can be discovered in aero plane construction.

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Science began with the wish of some prehistoric man to find out about the workings of the world about him. But the first recorded scientific discoveries are those of the ancient Babylonians who observed the positions of the sun, moon and planets. The ancient Egyptians invented simple arithmetic and geometry around 4,000 B.C. and acquired a considerable knowledge of engineering, medicine and anatomy.

      From about 600 B.C. the Greeks made great progress in philosophy and geometry, where intellectual effort only was required. But they achieved little advance in practical science, except for the discoveries of Aristotle (384-322 B.C.), who founded the study of biology. Archimedes (287-212 B.C.) discovered many simple principles of physics and Ptolemy (about A.D. 140) made advances in astronomy.

    Under Rome progress slowed down. Then the barbarians over-ran Europe and for almost 1,000 years – from 300-1100- science was kept alive first in Byzantium and then, from about 700, by the Arabs. From the 15th century, practical experiments in science began in earnest Galileo (1561626) carried out physical measurements and laboratory experiments. Francis Bacon (1561-1626) and Rene Descartes (1596-1650) pioneered the new scientific philosophy.

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Iron goes red when heated because its atoms radiate vibratory waves of an electromagnetic nature that are visible as light as a sufficiently high temperature. At 8000 C the iron is at low-red heat. But as the heat increases the iron will turn bright red, and finally white-hot and molten.

      Heat is passed through the iron by conduction-the contact of one iron particle with another with no dependence on particle movement. The heat which is given off as light when iron glows red-hot can be reconverted into heat by the substance on to which it falls. When iron is heated to a temperature below 3000 C it gives off invisible rays of infra-red radiation which are similar in nature to light. But they do not contain quite enough energy per unit (photon) to stimulate the optic nerve and do be seen by the human eye.

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       An electric iron is heated by a stream of electricity passing into the heating element in its base. This element may be cast into the sole plate of the iron or clamped to the plate in a herring-bone pattern.

     Hand irons have an electric loading up to 1,000 watts and weigh from 3-6 pounds. Many of them have thermostatic control so that the correct heat is maintained. Steam irons contain reservoirs of water which release steam through holes in the sole plate directly on to the article being ironed. In this way they produce, at the same time, the moisture, heat and pressure needed to make the fibers pliable and remove the creases.

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Guglielmo Marconi is usually credited with sending the first radio message. Marconi was born in Bologna, Italy; He came to England in 1896 and obtained a British patent for his wireless telegraphy system. In 1897 he established a radio transmitter on the roof of the post office at St Martin’s-Le-Grand in London, and sent a message a distance of a few hundred yards.

       He continued to improve his apparatus, and in 1898 radio was installed aboard a ship at sea, the East Goodwin lightship off the south-east coast of England. In the following year wireless messages were sent across the English Channel.

    The first radio transmission across the Atlantic was on December 12, 1901 from a station on the cliffs at poldhu, in Cornwall, and the message, three dots representing the letter S in the Morse code, was picked up at St John’s in Newfoundland.

     The existence of radio waves was first demonstrated by Heinrich Hertz, a German professor, in 1887. Marconi based his experiments on Hertz’s research.

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Glass is made naturally from a fusion of silica (sand), soda and lime. This fusion can be achieved merely by lightning striking in a place where the right ingredients happen to be adjacent to each other. When glass is made by man, other ingredients are added, such as potash, lead oxide and boric oxide. Some of these ingredients are used to make glass clear, some to colour it, and others to give it a frosted effect.

      Glass was made by potters in Egypt for glazing stone beads as early as 12,000 B.C. As Egyptian culture progressed, craftsmen used glass for the manufacture of personal ornaments and bottles.

    A tremendous step forward in the use of glass was made by the Phoenicians in about 300 to 200 B.C. by the invention of the blow-pipe. The blowpipe is a hallow iron tube with a mouthpiece at one end and a knob shape at the other. The knob-shaped end is dipped into hot, viscous glass. A “gather” of molten glass can be blown by the worker into a hollow ball. The more he blows, the larger the ball.

    During the Roman civilization the art of glass-making reached near perfection. In the 3rd Century, the Romans cast glass on flat stones and produced the first window panes. The break-up of the Roman Empire and the ensuring Dark Ages brought an end to such cultural developments. The glazing of windows did not become wide spread over the whole of Europe until the 15th and 16th Centuries.

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Water will boil anywhere, but it boils at different temperature in different places. For example, it will boil at a lower temperature up a mountain than at sea level.

      The boiling point of water is the temperature at which its vapour pressure becomes equal to the outside atmospheric pressure.

     As the atmospheric pressure is always changing so the boiling point of water will vary from day to day. Water boils at 1000 C only when the atmospheric pressure outside is at the “standard” value.

    At Quito in Ecuador, this is about 2,700 metres (or 8,800 feet) above sea level, water boils at about 900 C.

    People who explore in mountainous regions find a pressure cooker very useful. The time required to cook food can be greatly reduced if the boiling point of the water is raised. The pressure cooker does this, since it is an aluminum container fitted with a loaded pin valve which allows steam to escape. The valve can be set at varying pressures, enabling the food to be cooked at a temperature of about 1200 C.

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The first gas balloon, filled with hydrogen, was released in Paris is August, 1783 by a French professor of physics, J.A.C. Charles. Two months earlier, the first hot air balloon was sent aloft by the Montgolfier brothers, Jacques, Etienne and Joseph, of France. And it was with balloons of this type that the first manned flights were made.

         A rubberized silk balloon filled with hydrogen carried Professor Charles and M.N. Robert on a flight of 27 miles and rose to 2,000 feet. Ballooning became a popular spot in spite of the fact that hydrogen-filled balloons were always liable to catch fire. Some amazingly long trips were undertaken, including an unsuccessful attempt in 1958 to cross the Atlantic.

     Balloons play an important part in meteorology, the science concerned with the weather. The first aerial photographs were taken from balloons, and in the 1930s pressurized cabins or gondolas were designed enabling observers to rise over 60,000 feet into the stratosphere.

    Military observation balloons fastened to the ground by cables came into use at the end of the 18th Century and were employed by both North and South in the American Civil War (1861-1865)

 The Austrians used pilotless hot air balloons to bomb Venice in 1849. During the Franco-German War of 1870-1871 balloons transported mail and carrier pigeons. Barrage balloons tethered to the ground were used in the Second World War to provide barriers against low-flying enemy aircraft.

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An automobile is driven by an internal combustion engine which will work properly only if the right amounts of petrol and air are mixed together. The carburetor is the part of the engine where the mixing takes place.

     The burning of fuel in the engine is a chemical reaction in which petrol combines with the oxygen of the air to produce water, heat energy and oxides of carbon. A chemically correct mixture should have 15 parts of air to one part of petrol, both by weight. The amount of air then present is just sufficient to burn the petrol completely. If the engine uses a mixture with an excess of petrol a rich mixture-a small amount of unburnt petrol will be present in the exhaust fumes.

     A carburetor has to produce the required mixture to suit different engine conditions, such as starting, idling, acceleration, cruising and application of full power. It must be able to pass the correct mixture at all engine speeds and under varying loads, and has to atomize the petrol into tiny droplets and vaporize the resulting spray a combustible mixture.

     Inside the carburetor is a throttle valve which can increases or decreases the amount of mixture passing into the cylinders, which in turn control the power of the engine. This valve is mounted on a spindle which is operated by the accelerator pedal.

    A special device called a “strangler” or choke is also incorporated to help in starting the engine in cold weather by allowing an extra-rich mixture.

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