electrical engineering knowledgebase

Some useful articles for the electrical industry.

SI units In Europe and the UK, the units for measuring different properties are known as SI units. SI stands for Système Internationale.

All units are derived from seven base units. 

Time Seconds
Electrical current Ampere A
Length Metre m
Mass Kilogram kg
Temperature Kelvin K
Luminous intensity Candela cd
Amount of substance Mole mol

SI-derived units Derived quantity Name Symbol
Frequency Hertz Hz
Force Newton N
Energy, work, quantity of heat
Joule J Electric charge,
quantity of electricity Coulomb C
Power Watt W
Potential difference,electromotive force Volt V or U
electrical symbols IEEE
Capacitance Farad F
Electrical resistance Ohm Ω
Magnetic flux Weber Wb
Magnetic flux density Tesla T
Inductance Henry H
Luminous flux Lumen cd
Area Square metre m2
Volume Cubic metre m3
Velocity, speed Metre per second m/s
Mass density Kilogram per cubic metre kg/m3
Luminance Candela per square metre cd/m2
SI unit prefixes Name Multiplier Prefix
Power of 10 Tera 1000 000 000 000 T 1×1012
Giga 1000 000 000 G 1×109
Mega 1000 000 M 1×106
Kilo 1000 k 1×103 Unit 1
Milli 0.001 m 1×10−3
Micro 0.000 001 m 1×10−6
Nano 0.000 000 001 n 1×10−9
Pico 0.000 000 000 001 ρ 1×10−12
Examples mA Milliamp = one thousandth of an ampere
km Kilometre = one thousand metres
μv Microvolt = one millionth of a volt
GW Gigawatt = one thousand million watts kW Kilowatt = one thousand watts  


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