NAME='Robots'/> MY FORWARD WORK: What Is The International System Of Unit.

What Is The International System Of Unit.

Upendra Kumar

What- Is -The- International -System -Of -Unit.
BASE UNIT SYMBOL


In 1960, the general conference on weight and measures recommended that SI (System International d' Units) should replace all metric system now in use. The SI system of the unit for use in all aspects of life, including international trade, manufacturing, security, health, and safety, protection of the environment, and the basic science.






SI system has an edge over other versions of the metric system.

There are seven base units:-


    Physical  Quantity
        SI Units
          Unit Symbol
        Length
  meter
      m
        Mass
  kilogram
    kg
        Time
  second
    s
      Electric current
  ampere
A
      Luminous intensity
Candella
cd
      Thermodynamic
       temperature
kelvin
K
      Amount of substance
mole
mol

Definition

SECOND:-Second is the SI Unit of the Time and its unit symbol s. One second is equal to the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the unperturbed ground-state of the 133 Cs atom.

METER:- Meter is the SI Unit of the length and its unit symbol m. The one-meter equal to the length of the path traveled by light in vacuum during a time interval with a duration of 1/299792 of a second.

KILOGRAM:-The kilogram is the SI unit of the mass and its unit symbol kg. It is fixed numerical value of the plank constant h to be 6.62607015 X 10-34 when expressed in the unit j s, which is equal to kg m2 s−1, where the meter and the second are defined in terms of c and ΔνCs.

AMPERE:- The ampere is the SI unit of the electric current and its unit symbol A. It defined by taking the fixed numerical value of the elementary charge e to be 1.602 176 634 ×10-19. When expressed in unit C, which is equal to As where the second is defined in terms of ΔνCs.

KELVIN:- The kelvin is the SI unit of thermodynamic temperature and its unit symbol K, It is defined by taking the numerical value of Boltzmann constant k to be 1.380 649 ×10-23 when expressed in the unit J K-1 which is equal to kg m2 s-2 K-1, where the kilogram, meter and second are defined in terms of h, c, and ΔνCs.

MOLE:- The mole is the SI unit of amount of substance and its unit symbol mol.One mole contains exactly 6.022 140 76 × 1023elementary entities.

CANDELLA:-Candella is the SI unit of luminous intensity and its symbol cd. It is defined by taking the fixed numerical value of the luminous efficacy of monochromatic radiation of frequency 540 ×1012 Hz, Kcd, to be 683 when expressed in the unit lm W−1, which is equal to cd sr W−1, or cd sr kg−1 m−2 s3, where the kilogram, meter and second are defined in terms of h, c, and ΔνCs


There are supplementary Units. 


Physical  Quantity
SI Units
Unit Symbol
      Plan angle
          radian
      rad
      Solid angle
      steradian
        sr

Derived Units:- Units that are a combination of two or more quantities and which require a compound word to name them are called compound or derived units.
 
                                                         DERIVED UNITS


  Physical quantity
Name of the SI 
  Unit
SI Unit symbol
Force, weight
newton
N=kg m/s2
Work, energy, the quantity of 
       heat
joule
J=Nm
Power
watt
  W=J/s=Nm/s=Kg m2/s2


Pressure, stress
pascal
Pa=N/m2=kg/ms2
Frequency
hertz
Hz=s-1
Potential
volt
V=W/A
Resistance
ohm
𝝮=V/A=WA2
Customary
temperature
Degree celsius

0c







Size of Units: The choice of meter and kilogram as the base units of length and mass yield coherently derived units of more practical value in many cases. The meter, for instance, is a convenient unit for building site plans but it is too large for precision engineering purposes and too small for the large distance between the town and astronomical distance.


1 comment:

vaibhav said...

very interesting article.. really appreciating your work.. thank you..

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