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
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  Omega inverted 
G = 1 / R 
Impedance  Ohm  Z  Omega 

Resistivity  Ohm/meter/mm^{2} ( 20º) 
Ro 
Ro 
= Ohm /m / mm^{2} 
Capacitive Magnitudes 

Capacity  farad  C  F  C = load / voltage 
capacitive reactance  Ohm  Xc  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 

inductance  Henry  L  H Hr 
L = flow / current 
Inductive reactance  Ohm  Xl  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 

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 
Angular speed  Radian / Second  rad / s  Angular speed = rad / s  
Electromagnetic Magnitudes 

Electrical load  Culombio  Q  Q  1Q = 6.23.10^{18} 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 
MMF = I . Nº of helices 
Magnetic flux  Weber Maxwell 
Wb M 
Phi 
Wb = V . Second 
Magnetic induction  Tesla Gauss 
T G 
B  B = Magnetic flux / m^{2} 
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. cconsumption 
Photometric 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 / m^{2} 
Luminance  Candela / m^{2}  Cd / m^{2}  L  L = Cd / m^{2} 
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  ^{R}th  ^{R}th  ^{R}th = T / P. dissipated T = Increase of time 
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  
Admittance  Siemens  Y  S  
Speed  Meter / Second  V  m / s  V = m / s 
Speed of transmission of information 
Baud  bps  bps  bps = Bits . Second 