What Is The Difference Between Derived And Subsidiary Units?

Those units which are derived from the basic units of SI system are known as Derived units. For example: – the units of area are m2, which are derived from the basic units of length i.e. m.

It is most often we find the basic SI units not of convenient size for the measurement being done. For example: – m will be quite a bigger unit for expressing the length of a paper but too small for the distance between two cities. For this reason only, we use Subsidiary units confined to +ive and –ive powers of 10 times the basic SI unit.

The following table contains the Subsidiary units being used.

Prefix Symbol of Prefix Scientific Notation
atto a 10-18
femto f 10-15
pico p 10-12
nano n 10-9
micro µ 10-6
milli m 10-3
centi c 10-2
deci d 10-1
deca da 101
Hector h 102
kilo k 103
mega M 106
giga G 109
tera T 1012
peta P 1015
exa E 1018

The following table contains some commonly used Derived Units: -

Symbol Meaning SI Unit
A Area m2
V Volume m3
Ρ Density kg m-3
v Velocity m s-1
a Acceleration m s-2
F Force newton(N)= kg m s-2
p Pressure pascal(Pa)= N m-2
E Energy J=Nm kg m2 s-2
k Force constant N m-1
S Electric conductivity Ω-1 m-1
q Electric charge C(coulomb)
µ Dipole moment C m
Γ Frequency s-1 (Hz)
V Potential difference V(volt)
w Power W(watt)
C Capacitance f(farad)

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