# Electrical Units and Metric Prefixes

Electronics & ElectricalDigital ElectronicsMiscellaneous

A unit of measurement can be defined as a quantity chosen as a standard in terms of which other quantities may be expressed.

Engineering is an applied science dealing with a variety of physical quantities (a physical quantity is one which can be measured) like time, speed, voltage, resistance etc. Hence, for the measurement of these quantities standard units are defined.

There are a number of electrical units defined which are based on the SI system of units.

## Standard Electrical Units of Measurement

Electrical QuantitySymbol for QuantityMeasuring UnitSymbol for Unit
ChargeQ or qCoulombC
VoltageV or vVoltV
EMFE or eVoltV
CurrentI or iAmpereA
ResistanceR or rOhmΩ
InductanceLHenryH
ConductanceGMho or Siemen℧ or Ω-1or S
PowerPWattW
FrequencyfHertzHz
ImpedanceZOhmΩ

## Other Units for Electrical Measurement

Electrical QuantitySymbol for QuantityMeasuring UnitSymbol for Unit
Electrical EnergyW or EWatt – HourWh
Time PeriodTSeconds
Time ConstantτSeconds

## Multiples and their Metric Prefixes

In electrical and electronics engineering, a wide range of values are encountered between maximum and minimum values of a standard electrical unit. Hence, when the quantities being measured are very large or very small, then multiples of the electrical measuring units are used by placing a prefix with the unit.

Metric PrefixSymbolMultiplierPower of Ten
yottaY1,000,000,000,000,000,000,000,0001024
zettaZ1,000,000,000,000,000,000,0001021
exaE1,000,000,000,000,000,0001018
petaP1,000,000,000,000,0001015
teraT1,000,000,000,0001012
gigaG1,000,000,000109
megaM1,000,000106
kilok1000103
hectoh100102
decid1/1010-1
centic1/10010-2
millim1/100010-3
microμ1/1,000,00010-6
nanon1/1,000,000,00010-9
picop1/1,000,000,000,00010-12
femtof1/1,000,000,000,000,00010-15
attoa1/1,000,000,000,000,000,00010-18
zeptoz1/1,000,000,000,000,000,000,00010-21
yoctoy1/1,000,000,000,000,000,000,000,00010-24

Published on 29-May-2021 15:31:26