Prefixes
You have learned something of the units we use to measure voltage (V), current
(I), resistance (ohms ),
frequency (Hz) and power (W). However, sometimes we have either a lot or
a little of these and we find that working with either very large or small
numbers difficult.
This is the same as you have with money, a new car may cost you £10,000
but you do not refer to its price in pennies (which would be 1,000,000 pence)
because it is harder to work with.
Similarly, you refer to refer to the price of very cheap things in pennies
- you don't ask in a sweet shop for a 1/100 of a £1 chew !
We use this same trick in electronics but is a slightly different way.
If we have 1000 of something we use the letter k (note 'small' k) for kilo
to indicate thousands.
If we have 1,000,000 of something we use the letter M for Mega to indicate
millions.
If we only have 1/1000 of something we use the letter m (note 'small' m)
for milli to indicate one thousandth
We call these letters 'prefixes'. There is a graphic below to help you remember
the relative sizes of these prefixes. |