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

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