Notes on Units

Point of Interest  :I am providing you all  short concise notes on Units. Hope this helps. After Reading this  please attempt the Mcq's honestly.

Units : The chosen standard  used for measuring a physical quantity.

Units should be:
. well defined.
.easy to reproduce.
.easy to compare.
.internationally accepted.
.independent of changes in physical conditions.


Major Units classifications:
1) SI units
2) Mks units
3)Cgs units
4)Fps Units

Most important of all is SI units

There are 7 fundamental units given here:
1. length -----metre------m
2.mass--------kilogram---kg
3.time---------seconds-----sec
4.electric current ------ampere---A
5.Temperature----------kelvin----K
6.Luminous Intensity---Candela ---Cd
7. Amount of Substance----mole -----mol

Apart from this two supplementary units are:
radian --- for plane angle
steradian ----for solid angle.


Important units in Cgs system:
1. force -----dyne----1newton =10^5 dyne.
2. work ------erg------1 joule = 10^7 erg

Other Important Concepts:
Light year :amount of distance light travels in one year = 9.46 *10^15 mts
Tropical year : it is the year in which total solar eclipse occurs.
Leap year : February has 29 days .