System of Units:
» MKS system: In this system, unit of length is meter, mass is in kilogram & unit of time is second.
» CGS system: in this system, length is measured in centimeter, mass in gram & time in second.
» FPS system: In this system, length is measured in foot, mass in pound & time in second.
SI units:
International system of units ("SI", from the French "le Système International d' Unités") as defined by the international standards organization is used.
All SI units that are expressed as combinations of the base units. The SI base units are shown as follows:
Table of Fundamental Units
Supplementary Units
Quantities
|
Unit
|
Symbol
|
Plane Angle
|
Radian
|
rad
|
Solid Angle
|
Steradian
|
sr
|
Definitions of SI Base Units:
Meter (m): The meter (abbreviation ‘m’) is the SI unit of displacement or length. One meter is the distance traveled by a ray electromagnetic energy through a vacuum in 1/299,792,458 second. The meter was originally defined as one ten-millionth ($10^{-7}$) of the distance.
Kilogram (kg): The kilogram (abbreviation ‘kg’) is the SI unit of mass. It is defined as the mass of a particular international prototype made of Platinum-iridium and kept at the international Bureau of weights & measures. It was originally defined as the mass of one liter ($10^{-3}$ cubic meter) of pure water.
Second (S): The second (abbreviation ‘sec’ or ‘s’) is the SI unit of time. One second is the time that elapses during $9.912631770 * 10^9$ cycles of the radiation produced by the transition between two levels of Cesium 133 atoms.
It is also the time required for an EM field to propagate 299.792,458 meters through a vacuum.
Kelvin (K): The kelvin (abbreviation K) is the SI unit of temperature. One Kelvin is $1/273.16\;\;(3.6609 * 10^{-3})$ of the thermodynamic temperature of the triple point of pure water ($H_2O$).
Ampere (A): The ampere (abbreviation, A) is the SI unit of electric current. One ampere is the current that would produce a force of $0.0000002 \;\; (2 * 10^{-7})$ newton between two straight, parallel, perfectly conducting wires having infinite length. Whose diameter is zero, separated by one meter in a vacuum. One ampere represents $6.24 * 10^{18}$ unit electric charge carriers, such as electrons, passing a specified fixed point in one second.
Candela (cd): The candela (abbreviation, cd) is the SI unit of luminous intensity. It is the electromagnetic (EM) radiation, in a specified direction. That has an intensity of $1/683 \;\; (1.46 * 10^{-3})$ watt/steradian at a frequency of 540 terahertz ($5.40 * 10^{14}$ hertz).
Mole (mol): The mole (abbreviation, mol) is the SI unit of material quantity. One mole is the number of atoms in 0.012 kilogram of the most common isotope of elemental carbon ($C-12$). This is approximately $6.022169 * 10^{23}$ , and is also called the Avogadro constant.
Advantage of SI – Units:
- It is a rational system of units.
- It is a coherent system of units.
- It is a decimal system.
- It is highly useful in practical and theoretical work.
The smaller and larger values of Physical Quantities are expressed in power of 10.
SI Prefix
|
|||||
Name
|
Symbol
|
Factor
|
Name
|
Symbol
|
Factor
|
Deca
|
da
|
$10^1$
|
Deci
|
d
|
$10^{-1}$
|
Hecto
|
h
|
$10^2$
|
Centi
|
c
|
$10^{-2}$
|
Kilo
|
k
|
$10^3$
|
milli
|
m
|
$10^{-3}$
|
Mega
|
M
|
$10^6$
|
micro
|
$\mu$
|
$10^{-6}$
|
Giga
|
G
|
$10^9$
|
nano
|
n
|
$10^{-9}$
|
Tera
|
T
|
$10^{12}$
|
pico
|
p
|
$10^{-12}$
|
Peta
|
P
|
$10^{15}$
|
femto
|
f
|
$10^{-15}$
|
Exa
|
E
|
$10^{18}$
|
atto
|
a
|
$10^{-18}$
|
Zetta
|
Z
|
$10^{21}$
|
zepto
|
z
|
$10^{-21}$
|
Yotta
|
Y
|
$10^{24}$
|
yocto
|
y
|
$10^{-24}$
|
This is a recent upgrade about the Standard Units. Click here.
Return to Main Menu