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Electrical Magnitudes, Units and Symbols

The physical magnitude is all that property that can be measured and its result expressed by a number that indicates its quantity based on one unit. These quantities can be multiples or submultiples of the unit and their values are represented in the International System with abbreviation and symbols.

On this page we show the fundamental physical quantities related to electrical science and engineering and the like, along with their units, abbreviation, symbols and basic calculations.

Quantities, units, abbreviations, symbols and basic calculations

Magnitud Unit Abbreviation Symbol Basic calculation

Electrical Basic Magnitudes

Electric current Amp I A I = V / R
V - voltage
R - resistance
Voltage Volt V
U
V V = R . I
R - resistance
I - electric current

Resistive Magnitudes

Electrical resistance Ohm R
Omega
R = V / I
Ohm's law
Conductance Siemens
Mho
G
Inverted Omega
G = 1 / R
Impedance Ohm Z
Omega

Resistivity Ohm / meter / mm2
( 20º)

Ro

Ro
= Ohm / m / mm2

Capacitive Magnitudes

capacitive reactance Ohm Xc
Omega
Xc = 1 / pulsation . capacity
Coefficient lost capacitor In decimal No. d d d = Xc / Rp
Rp = resistance losses
Capacitor quality factor In decimal No. Q Q Q = 1 / d
Dielectric Constant Farad / meter     F / m

Inductive Magnitudes

inductance Henry L H
Hr
L = flow / current
Inductive reactance Ohm Xl
Omega
XL = Pulsation / L
Coefficient lost coils
inductors
In decimal No. d d d = R / XL
Quality factor of the coils
inductors
In decimal No. Q Q Q = XL / R
Permeability Henry / meter     H / m

Electrical Signal magnitudes

Frequency Hertz F Hz F = 1 / T
T = period
Frequency = Cycle
Wavelength Meter
Landa

Landa
= Speed . frequency
Pulsation 1 / seconds
Minuscule omega

Minuscule omega
= 2 . Pi . Frequency
Period Seconds T T T = 1 / F

Electromagnetic Magnitudes

Electrical load Culombio Q Q 1Q = 6.23.1018 electrons
Intensity of electrical field Voltage / length E E E = Voltage / length
Intensity of magnetic field Gauss
Ampere / meter
H H H = MMF / length
Magnetomotriz forces Gilbert
Ampere - return
MMF
Theta
MMF = I . No of turns
Magnetic flux Weber
Maxwell
Wb
M

Phi
Wb = V . Second
Magnetic induction Tesla
Gauss
T
G
B B = Magnetic flux / m2

Magnitudes of Electrical Work

Electrical power Watt P W P = V . I
Current density Ampere / mm2 J J J = I / mm2
Electrical work Watt / second
( Joule )
W Ws W = Power . Time
Electrical performance Decimal Nº
% Percentage

Eta

Eta
= P. output / P. consumption

Ilumination magnitudes

Luminous flow Lumen Lm
Phi

Luminous Intensity Candela cd cd
Luminous efficacy Lumen / Watt cd
Eta
cd = Lm / Watt
Lighting Lux Lx E Lx = Lm / m2
Luminance Candela / m2 Cd / m2 L L = Cd / m2

Thermal Magnitudes

Temperature Degrees Celsius
Degrees Fahrenheit
Degrees Kelvin
T ºC
ºF
ºK

Heat quantity Joule
Kilocalorie
J
Kcal
Q 1 Kcal = 1000 cal = 4180 J
Calorific capacity Joule / K
Kilocalorie / K
J / K
Kcal / K
K
Thermal resistance K / W Rth Rth Rth = T / P. dissipated
T = Increase of temperature

General Magnitudes in the Physics

Time Second t s
Length Meter L m
Force Newton F N
Mass Gram m g
Energy Joule E J
Pressure Pascal P Pa
Sonority and logarithmic scales of power Bel - Decibel dB dB db = Bel / 10

Other Magnitudes

Susceptance Siemens B S