S.I. Units of Physical Quantity

Unit-The chosen standard used for measuring a physical quantity is called unit.
Unit should be:

Well defined
Easy to reproduce
Easy to compare
Internationally accepted
Independent of changes in physical conditions

Units are of two types:

Fundamental Unit :
- Are expressed in terms of standard units.
- There are seven (7) basic physical quantities.
- Examples- mass, length, time, electric current, temperature, luminous intensity and amount of substance.
- All other quantities are expressed in terms of these quantities.
Derived Unit :
- When a physical quantity expresses itself in terms of two or more fundamental physical quantities.
- It is derived by multiplying or dividing one basic physical quantity with another basic physical quantity.
- Examples- density, volume, force, power, velocity, acceleration etc.

System of Units –Units depends on choice .each choice of units leads to a new system of units. The internationally accepted systems are
i) CGS System ii) MKS System iii) FPS System iv) SI Units.
In SI Units(International System of Units)- There are seven fundamental units and 2 supplementary units.All the units which are defined/ expressed in terms of fundamental units are called derived units.such as force work etc.
Here list of most often used physical quantities their unit and symbols.

Quantity	SI	Symbol
Length	Meter	M
Mass	Kilogram	Kg
Time	Second	S
Work and Energy	Joule	J
Electric Current	Ampere	A
Temperature	Kelvin	K
Intensity of flame	Candela	Cd
Angle	Radian	Rad
Solid angle	Steredian	Sr
Force	Newton	N
Area	Square meter	M2
Volume	Cubic meter	M3
Speed	Meter per second	Ms-1
Angle Velocity	Radian per second	Rad s-1
Frequency	Hertz	Hz
Moment of inertia	Kilogram square meter	Kgm2
Momentum	Kilogram meter per second	Kg ms-1
Impulse	Newton second	Ns
Angular Momentum	Kilogram square meter per second	Kgm2s-1
Pressure	Pascal	Pa
Power	Watt	W
Surface tension	Newton per meter	Nm-1
Viscosity	Newton second per square m.	N.s.M-2
Thermal Conductivity	Watt per meter per degree celcius	Wm-1c-1
Specific Heat capacity	Joule per kilogram per Kelvin	Jkg-1K-1
Electric charge	Coulomb	C
Potential Difference	Volt	V
Electric Resistance	Ohm	O
Electrical Capacity	Farad	F
Magnetic Induction	Henry	H
Magnetic Flux	Weber	Wb
Or photometric power	Lumen	Lm
Intensity of illumination	Lux	Lx
Wave length	Angstrom	A0
Astronomical distance	Light year	ly