# Metric Prefixes and SI Units

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Contributors: JordanDee

## SI Units

We've been measuring stuff for millennia, and our units used for those measures have been evolving since then. There are now dozens of units to describe physical quantities. For example, length can be measured by the foot, meter, fathom, chain, parsec, league, and so on. In order to better communicate measurements, we needed a standardized system of units, which every scientist and measurer could use to share their findings. This standardized system has come to be called the \ International System of Units \</epic voice>, abbreviated SI.

### Physical SI Units

QuantitySI UnitUnit Abbreviation
Timeseconds
Lengthmeterm
Massgramg
TemperaturekelvinK
ForcenewtonN

While we can still use units like feet or miles for distance (instead of meters), liters to describe volume (instead of m3), and Fahrenheit or Celsius to describe temperature (instead of °K), the units above are a standardized way for every scientist to share their measurements. Using the units above means everyone is speaking the same language.

### Common Electronics Units

In dealing with electronics, there are a handful of units we'll be encountering more often than others. These include:

QuantitySI UnitUnit Abbreviation
Electric Potential Difference (Voltage)voltsV
Electric CurrentampereA
PowerwattW
Energy/Work/HeatjouleJ
Electric ChargecoulombC
ResistanceohmΩ