Electrical Magnitudes, Units and Symbols

Listing the main physical quantities (current, resistance, voltage, frequency ...) involved in electrical phenomena, together with its units, abbreviations, symbols and basic calculations

Quantities, units, abbreviations, symbols and basic calculations

Magnitud Unit Abbreviation Symbol Basic calculation

Electrical Basic Magnitudes

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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

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Electrical resistance Ohm R Omega
Omega
R = V / I
Ohm's law
Conductance Siemens
Mho
G Omega invertida
Omega inverted
G = 1 / R
Impedance Ohm Z Omega
Omega
 
Resistivity Ohm/meter/mm2
( 20º)
Ro
Ro
Ro
Ro
Ro = Ohm /m / mm2

Capacitive Magnitudes

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

Inductive Magnitudes

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

Magnitudes in Alternate Signs

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Frequency Hertz F Hz F = 1 / T
T = period
Frequency = Cycle
Wavelength Meter Landa
Landa
Landa
Landa
Landa = Speed . frequency
Pulsation 1 / seconds Omega minúscula
Minuscule omega
Omega minúscula
Minuscule omega
Omega minúscula= 2 . Pi . Frequency
Period Seconds T T T = 1 / F
Angular speed Radian / Second   rad / s Angular speed = rad / s

Electromagnetic Magnitudes

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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 / Longitud
Magnetomotriz forces Gilbert
Ampere - return
MMF Theta
Theta
MMF = I . Nº of helices
Magnetic flux Weber
Maxwell
Wb
M
Phi
Phi
Wb = V . Second
Magnetic induction Tesla
Gauss
T
G
B B = Magnetic flux / m2

Magnitudes of Electrical Work

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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
Eta
Eta
Eta = P. output / P. cconsumption

Photometric Magnitudes

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

Thermal Magnitudes

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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 = DeltaT / P. dissipated
DeltaT = Increase of time

General Magnitudes in the Physics

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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

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Susceptance Siemens B S  
Admittance Siemens Y S  
Speed Meter / Second V m / s V = m / s
Speed of transmission
of information
Baud bps bps bps = Bits . Second
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