International System of Units SI
Sevres, French Republic based International Bureau of Weights too Measures, serves equally a depository for the primary international standards too equally a laboratory for certification too intercomparison of national criterion copies. In 1960, the SI organization was built upon the MKS system, that is, metre-kilogram-second system, which has 7 basic units. These are equally follows :-
Metre (unit of length; Symbol m) defined equally the distance travelled yesteryear lite inward a vacuum inward 1/299,792,458 second;
Kilogram (unit of weight; Symbol kg) which equals 1,000 grams equally defined yesteryear the international epitome kilogram of platinum-iridium inward the keeping of the International Bureau of Weights too Measures;
Second (unit of time; Symbol s), the duration of 9,192,631,770 periods of radiations associated alongside a specified transition of the cesium-133 atom;
Ampere (unit of electrical current; Symbol A), which is the electrical current that, if maintained inward ii wires placed 1 metre apart inward a vacuum, would -produce a forcefulness of 2 x 10-7 Newton per metre of length;
Candela (unit of luminous intensity; Symbol cd), defined equally the intensity inward a given administration of a rootage emitting radiations of frequency 540 x 1012 hertz too that has a radiant intensity inward that administration of 1/683 watt per steradian;
Mole (unit of amount of substance; Symbol mol), defined equally containing equally many simple entities of a meat equally in that location arc atoms inward 0.012 kilogram of carbon-12
Kelvin (unit of temperature; Symbol K) which is 1/273.16 of the thermodynamic temperature of the triple quest (equilibrium amidst the solid, liquid, too gaseous phases) of pure water.
Units of Scientific Measurement
Atomic Weight : The weight of an atom of hydrogen is taken equally the standard; the respective weights of the atoms of all other substances are expressed inward price 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 equally the atom of hydrogen.
Angstrom : Unit of wavelength of lite is Angstrom. 1 Angstrom = 10-8 cm. There is a bigger unit of measurement for measurement the wavelength of infra-red light; it is called a milli-micron too is equal to 10-7 cm. Micron = 10-4 cm, is a nevertheless bigger unit.
Bar : Unit of atmospheric pressure; 1 bar is equal to a pressure level of 106 dynes per sq cm.
Calorie : Unit of heat. It is the amount of oestrus required to heighten the temperature of 1 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 pose out energy consumed inward 1 2nd inward an electrical circuit through which a electrical current pose out energy of 1 ampere is flowing against a potential divergence of 1 volt.
Knot : Measure to know the speed of a ship.
Light Year : H5N1 lite twelvemonth is the distance lite travels inward 1 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 equally a unit of measurement for measurement stellar distances.
Nautical Mile : H5N1 unit of measurement of distance used inward navigation. One infinitesimal of longitude measured along the Equator. H5N1 Nautical Mile is roughly equal to 6,080 feet.
Pressure : The pressure level is expressed inward pounds weight per sq cm. The pressure level of the atmosphere is expressed inward millibars. One millibar = 1 dyne per sq cm. If the pressures are rattling high, they are expressed inward multiples of atmospheric pressure. 1 atmosphere is a pressure level exerted yesteryear a column of mercury 76 cm high at bounding main degree too at a latitude of 45°.
Quintal : Metric mensurate of weight; 100 kilograms = 1 quintal.
1 ton = 10 quintal = M kg.
Volt : The unit of measurement of potential difference. It is that much potential divergence which when applied to the ends of an electrical conductor of resistance 1 ohm, the amount of pose out energy consumed inward the circuit inward 1 2nd is 1 Joule (=107 ergs).
