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Define prefixes. Interconvert the prefixes and their symbols to indicate multiples and sub-multiples for both bases and derived units?

Difficulty: Medium

Prefixes:

          Prefixes are the words or letters added before Si units such as kilo, mega, giga and milli.

         SI units have the advantage that their multiples and sub-multiples can be expressed in terms of prefixes. These prefixes are given in Table.

                                                             Some Prefixes

Prefix

Symbol

Multiplier

exa

E

1018

peta

P

1015

tera

T

1012

giga

G

109

mega

M

106

Kilo

K

103

hecto

h

102

deca

da

101

deci

d

10-1

centi

c

10-2

milli

m

10-3

micro

M

10-6

nano

n

10-9

Pico

P

10-12

femto

f

10-15

atto

a

10-18

Advantages of prefixes:

       The prefixes are useful to express very large or small quantities. For example, divide 20,000 g by 1000 to express it into kilogram, since kilo represents 103 or 1000.

Thus 20,000g = 20,000 ÷ 1,000Kg  = 20kg

or    20,000 g     = 20 x 10g             = 20kg

Note:

Double prefixes are not used. For example, no prefix is used with kilogram since it already contains the prefix kilo.

           Prefixes given in Table are used with both types of base and derived units.

Multiples and sub-multiples of length:

1km

103m

1cm

102m

1mm

10-3m

1µm

10-6m

1nm

10-9m

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