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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