International System of Units SI
Sevres, French Republic based International Bureau of Weights in addition to Measures, serves every bit a depository for the primary international standards in addition to every bit a laboratory for certification in addition to intercomparison of national measure copies. In 1960, the SI organisation was built upon the MKS system, that is, metre-kilogram-second system, which has 7 basic units. These are every bit follows :-
Metre (unit of length; Symbol m) defined every bit the distance travelled past times calorie-free inwards a vacuum inwards 1/299,792,458 second;
Kilogram (unit of weight; Symbol kg) which equals 1,000 grams every bit defined past times the international paradigm kilogram of platinum-iridium inwards the keeping of the International Bureau of Weights in addition to Measures;
Second (unit of time; Symbol s), the duration of 9,192,631,770 periods of radiations associated amongst a specified transition of the cesium-133 atom;
Ampere (unit of electrical current; Symbol A), which is the electrical flow that, if maintained inwards 2 wires placed i metre apart inwards a vacuum, would -produce a forcefulness of 2 x 10-7 Newton per metre of length;
Candela (unit of luminous intensity; Symbol cd), defined every bit the intensity inwards a given direction of a root emitting radiations of frequency 540 x 1012 hertz in addition to that has a radiant intensity inwards that direction of 1/683 watt per steradian;
Mole (unit of amount of substance; Symbol mol), defined every bit containing every bit many uncomplicated entities of a core every bit at that topographic point arc atoms inwards 0.012 kilogram of carbon-12
Kelvin (unit of temperature; Symbol K) which is 1/273.16 of the thermodynamic temperature of the triple signal (equilibrium amid the solid, liquid, in addition to gaseous phases) of pure water.
Units of Scientific Measurement
Atomic Weight : The weight of an atom of hydrogen is taken every bit the standard; the respective weights of the atoms of all other substances are expressed inwards damage of it. So when it is stated that the atomic weight of Fe is 56, it is meant that the atom of Fe is 56 times every bit the atom of hydrogen.
Angstrom : Unit of wavelength of calorie-free is Angstrom. 1 Angstrom = 10-8 cm. There is a bigger unit of measurement for measure the wavelength of infra-red light; it is called a milli-micron in addition to is equal to 10-7 cm. Micron = 10-4 cm, is a withal bigger unit.
Bar : Unit of atmospheric pressure; i bar is equal to a pressure level of 106 dynes per sq cm.
Calorie : Unit of heat. It is the amount of estrus required to enhance the temperature of i gram of H2O through 1°C.
Horse Power : The practical unit of measurement of power. The ability of an agent which tin function at the charge per unit of measurement of 550 foot-pounds per 2nd or 33,000 foot-pounds per minute. 1 HP = 746 watts
joule: Unit of function or energy. It is equal to 10-7 ergs. It is the liberate energy consumed inwards i 2nd inwards an electrical circuit through which a electrical flow liberate energy of i ampere is flowing against a potential departure of i volt.
Knot : Measure to know the speed of a ship.
Light Year : H5N1 calorie-free yr is the distance calorie-free travels inwards i hateful 'solar year, at a speed of 1,86,000 miles per second. It is equal to 5,880,000,000,000 miles. It is used every bit a unit of measurement for measure stellar distances.
Nautical Mile : H5N1 unit of measurement of distance used inwards navigation. One infinitesimal of longitude measured along the Equator. H5N1 Nautical Mile is unopen to equal to 6,080 feet.
Pressure : The pressure level is expressed inwards pounds weight per sq cm. The pressure level of the atmosphere is expressed inwards millibars. One millibar = 1 dyne per sq cm. If the pressures are real high, they are expressed inwards multiples of atmospheric pressure. 1 atmosphere is a pressure level exerted past times a column of mercury 76 cm high at body of body of water degree in addition to at a latitude of 45°.
Quintal : Metric stair out of weight; 100 kilograms = 1 quintal.
1 ton = 10 quintal = chiliad kg.
Volt : The unit of measurement of potential difference. It is that much potential departure which when applied to the ends of an electrical conductor of resistance i ohm, the amount of liberate energy consumed inwards the circuit inwards i 2nd is i Joule (=107 ergs).
