Unit of length-Metre(m)
Metre is the distance traveled by a ray of electromagnetic (EM) energy through a vacuum in 1/299,792,458 (3.33564095 x 10^-9 ) second. The meter was originally defined as one ten-millionth (0.0000001 or 10^-7 ) of the distance, as measured over the earth’s surface in a great circle passing through Paris, France, from the geographic north pole to the equator.The metre is the length equal to 1650 673.73 wavelength is vaccum of the transition of the krypton 86 atom.
Unit of Mass-kilogram(kg)
It is defined as the mass of a particular international prototype made of platinum-iridium and kept at the International Bureau of Weights and Measures. It was originally defined as the mass of one liter (10^-3 cubic meter) of pure water.
Unit of time -second(s)
One second is the time that elapses during 9.192631770 x 10^9 cycles of the radiation produced by the transition between two levels of Cesium 133. It is also the time required for an EM field to propagate 299,792,458 (2.99792458 x 10^8 ) meters through a vacuum.
Unit of Thermodynamic Temperature-kelvin(K)
One Kelvin is 1/273.16 (3.6609 x 10^-3 ) of the thermodynamic temperature of the triple point of pure water (H 2 O).
Unit of Electric Current-Ampere(A)
One ampere is the current that would produce a force of 0.0000002 (2 x 10^-7 ) newton between two straight, parallel, perfectly conducting wires having infinite length and negligible diameter, separated by one meter in a vacuum. One ampere represents 6.24 x 10^18 unit electric charge carriers, such as electrons, passing a specified fixed point in one second.
Unit of Luminous Intensity-candela(cd)
It is the electromagnetic radiation, in a specified direction, that has an intensity of 1/683 (1.46 x 10^-3 ) watt per steradian at a frequency of 540 terahertz (5.40 x 10 ^14 hertz). The candelais in the perpendicular direction of a surface of 1/600.000 square metre of a black body at the temperature of freezing platinum,under a pressure of 101.325 newton per square metre.
Unit of amount of substance-mole(mol)
One mole is the number of atoms in 0.012 kilogram of the most common isotope of elemental carbon (C-12). This is approximately 6.022169 x 10^23 , and is also called the Avogadro constant.
How the Basic SI Units are formed?
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