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Showing posts from March, 2010

general science#12

Distribution of elements on the surface of the earthElement Distribution Element Distribution Oxygen 49.85% Silicon 26.03% Aluminium 7.28% Calcium 3.18% Sodium 2.33% Potassium 2.23% Magnesium 2.11% Hydrogen 0.97% Titanium 0.41% Chlorine 0.20% Carbon 0.19% Others 1.00% Metals and their oresSubstance Ore Substance Ore Calcium Limestone, marble, chalk Mercury Cinnabar Copper Copper pyrites, Cuprite Potassium Carnelite, Saltpetre Cement Limestone and clay Sodium Rock salt, Cryolite Glass Silica and lime stone Thorium Monozite Iodine Sea weeds Titanium Rutile, limenite Iron Hematite, Magnatite, Iron pyrites Uranium Pitchblende Gold Aurite Silver Argentite Metals and their alloys Alloy Component Brass Copper, Zinc Bronze Copper, Tin, Zinc Gun metal Copper, Tin, Zinc Duralmin Aluminium, Copper, Magnesium, Manganese Solder Aluminium, Lead, Tin Pewter Lead, Tin

general science#11

Unitsatmosphere, technical atmosphere
mm, cm, inches of mercurymm, cm, inch, foot of waterkip, ton-force, pound-forcepound per square inchbar, decibar, millibarbarye, dynesthene per square metre, piezePressure in everyday life
Transpirational pull in plants (negative pressure caused by surface tension), used to suction water from the water to leavesCasimir effect: physical force betwen two uncharged metal plates in vaccuum. Used in nanotechnologyAtmospheric pressure decreases with elevation. Due to this boiling point of water decreases with elevationBlood pressure is the pressure exerted by circulating blood on the walls of blood vessels. For a healthy adult human the pressure should be 115 mm Hg (systolic) and 75 mm Hg (diastolic)A microphone works on the principle of sound pressure. A thin membrane converts sound pressure into an electrical signalCaisson Disease (aka The Bends or Decompression Sickness) occurs due to sudden change in atmospheric pressure. It happens whe…

general science#10


Heat is the process of energy transfer from one system to anotherUnits of heat: Joules (J), Calories, British Thermal Unit (BTU)Temperature is a measure of internal energy (enthalpy)Heat transfer can happen spontaneously only from a warmer to a colder body. Reverse heat transfer can only happen with the aid of an external source such as a heat pump.Mechanisms of heat transfer

Conduction is the most significant heat transfer mechanism in solids. It occurs as hot high energy molecules interact with neighbouring and transfer heat to them. Eg: heat transfer from one end of a metal rod to another
Convection is most significant in liquids and gases. This happens when hot molecules move and transfer energy to other molecules. Eg: boiling of water. When water is heated on a stove, hot water from the bottom rises and displaces colder liquid which falls.
Radiation is the only form of heat transfer possible in the absence of a medium. Heat is transferred in the form of electro…