SI System: - It is an International system of unit. S.I. stands for It based upon seven fundamental, two supplementary and a large no. of derived units
SI Base Quantities and Units:-
Length :- metre m The metre is the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second. (1983)
Mass:- kilogram kg The kilogram is equal to the mass of the international prototype of the kilogram (a platinum-iridium alloy cylinder) kept at international Bureau of Weights and Measures, at Sevres, near Paris, France. (1889).
Time:- second s The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom.
(1967).
Electric Current:- ampere A The ampere is that constant current which, if maintained in current two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2×10–7 newton per metre of length. (1948)
Temperature:- kelvin K The kelvin, is the fraction 1/273.16 of the thermodynamic dynamic temperature of the triple point of water. (1967) Temperature
Amount of Substance:- mol The mole is the amount of substance of a system, which contains substance as many elementary entities as there are atoms in 0.012 kilogram of carbon - 12. (1971)
Luminous Intensity:- candela cd The candela is the luminous intensity, in a given intensity direction, of a source that emits monochromatic radiation of frequency 540 Tera hertz and that has a radiant intensity in that direction of 1/683 watt per steradian. (1979)
Supplementary Units:
(a) Plane angle dθ is defined as the ratio of length of arc ds to
the radius r .
(b) Solid angle dΩ is defined as the ratio of the intercepted area
dA of the spherical surface, described about the apex O as the
centre, to the square of its radius r, as shown in fig. (b)
The unit for plane angle is radian with the symbol rad and the unit for the solid angle is steradian with the symbol sr. Both these are dimensionless quantities.
SI Base Quantities and Units:-
Length :- metre m The metre is the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second. (1983)
Mass:- kilogram kg The kilogram is equal to the mass of the international prototype of the kilogram (a platinum-iridium alloy cylinder) kept at international Bureau of Weights and Measures, at Sevres, near Paris, France. (1889).
Time:- second s The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom.
(1967).
Electric Current:- ampere A The ampere is that constant current which, if maintained in current two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2×10–7 newton per metre of length. (1948)
Temperature:- kelvin K The kelvin, is the fraction 1/273.16 of the thermodynamic dynamic temperature of the triple point of water. (1967) Temperature
Amount of Substance:- mol The mole is the amount of substance of a system, which contains substance as many elementary entities as there are atoms in 0.012 kilogram of carbon - 12. (1971)
Luminous Intensity:- candela cd The candela is the luminous intensity, in a given intensity direction, of a source that emits monochromatic radiation of frequency 540 Tera hertz and that has a radiant intensity in that direction of 1/683 watt per steradian. (1979)
Supplementary Units:
(a) Plane angle dθ is defined as the ratio of length of arc ds to
the radius r .
(b) Solid angle dΩ is defined as the ratio of the intercepted area
dA of the spherical surface, described about the apex O as the
centre, to the square of its radius r, as shown in fig. (b)
The unit for plane angle is radian with the symbol rad and the unit for the solid angle is steradian with the symbol sr. Both these are dimensionless quantities.
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