System of units

The International System of Units (abbreviated as SI, from the French Système international (d'unités)) is the modern form of the metric system, and is the most widely used system of measurement. It comprises a coherent system of units of measurement built on seven base units and a set of twenty prefixes to the unit names and unit symbols that may be used when specifying multiples and fractions of the units. The system also specifies lowercase names for 22 derived units.

The system was published in 1960 as a result of an initiative that began in 1948. It is based on the metre–kilogram–second system of units (MKS) rather than any variant of the centimetre–gram–second system of units (CGS). SI is intended to be an evolving system, so prefixes and units are created and unit definitions are modified through international agreement as the technology of measurement progresses and the precision of measurements improves. The 24th and 25th General Conferences on Weights and Measures (CGPM) in 2011 and 2014, for example, discussed a proposal to change the definition of the kilogram, linking it to an invariant of nature rather than to the mass of a material artefact, thereby ensuring long-term stability.[1]

The motivation for the development of the SI was the diversity of units that had sprung up within the CGS systems and the lack of coordination between the various disciplines that used them. The CGPM, which was established by the Metre Convention of 1875, brought together many international organisations to not only agree on the definitions and standards of the new system but also agree on the rules for writing and presenting measurements in a standardised manner around the world.

The International System of Units has been adopted by all developed countries except the United States.[citation needed]

1. System Of Units Represented By : Shreeshay Desai Omprakash Chauhan Adnan Mulani Nashra Patel Muchhala Polytechnic

2. International System of Units (SI ) The International System of Units (abbreviated  SI  from  systeme internationale  , the French version of the name) is a scientific method of expressing the magnitudes or quantities of important natural phenomena. There are seven base units in the system, from which other units are derived. This system was formerly called the meter-kilogram-second (MKS) system. Intoduction

3. The first is the number which indicates the magnitude of quantity and second indicates the standered . e.g : 3 magnitude metre Name of the unit (standard) i.e. how many times of standard unit.

4. Fundamental unit Derived unit The units of fundamental quantities are called fundamental units. It does not depend on any other unit. e.g . : length – m, mass – kg. The units used to measure derived quantities are called derived units. It depends on fundamental units for their measurement. e.g . : speed – m/s, density – kg/m³ Units Unit : The standard used for measurement of a physical quantity is called unit of that quantity. e.g. : 3 meter is the length of table. Here metre is the unit used for the measuremnt of the length.

5. Fundamental Quantities and F undamental Units Fundamental Quantities : The physical quantities which do not depend on any other physical quantities for their measurement are called fundamental quantities. Fundamental Units : The units used to measure fundamental quantities are called fundamental units.

6. Derived Quantities and Derived Units Derived Quantities : Physical quantities which depend on one or more fundamental quantities for their measurement are called derived quantities. Derived Units : The units used to measure derived quantities are called derived units.

7. System of unit : A syatem of unit, is a class of units consisting components from a fundamental set of units. C.G.S System : I n this system, the units of length, mass and time are C entimetre , G ram and S econd respectively. M.K.S. System : In this system, the units of length, mass and time are M etre , K ilogram and S econd respectively. F.P.S. System : In this system, the units of length, mass and time are F oot, P ound and S econd respectively. S.I. System : S.I. is the abbreviation of the French name System Internationale (International system of units.) C.G.S. System M.K.S. System F.P.S. System S.I. System System of unit

8. Error, Types of Errors. Error : An error is a fault, which may occur even in the most careful observation ( i ) Instrumental error (ii) Personal error (iii) Error because of external causes (iv) Error Because of defect in the system Systematic error Types of Error ( i ) Instrumental error (ii) Systematic error (iii) Random error

9. Instrumental error : The error because of wrong adjustment or defective setting of the instrument is called as instrumental error. Personal error : this error is due to carelessness or fault of an observer while taking readings. Error because of external causes : this error arise due to changes in environmental conditions. Error due to defect in the system : This error is because of defective experimental setup. Commonly Or Mostly Used Error Method

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