<<

Electrical Units

Ratio of SI unit Magnitude of Quantity Symbol Equation SI unit symbol CGS unit SI to cgs unit Z Current , i I=/; I = E/Z; I = Q/t A 10-1 Quantity Q, q Q = it; Q = CE C 10-1 E, e E = IR; E = W/Q V 108 Resistance R, r R=E/I; R = ␳l /A 109 Resistivity ␳␳= RA / I Ohm- Ω•m Abohm-cm 1011 Conductance G, g G =␥ A / l G = A/␳l S 10-9 Conductivity ␥␥ = 1/␳; ␥ = I/ RA Siemens/meter S/m Abmho/cm 10-11 C C = Q/E F Abfarad* 10-9 /meter F/m Stat farad*/cm 8.85 X 10-12

Relative permittivity ⑀r ⑀r = ⑀ր⑀␱ Numerical Numerical I Self- L L = - N(d␾րdt) H 109 1/2 9 Mutual inductance M M = K(L1L2) Henry H Abhenry 10 J J = eit J 107 kwh kwh = kw/3600; 3.6 MJ Kilowatthour kWh 36 X 1012 Active W W = J/t; W = EI cos ⍜ W Abwatt 107 Reactive power jQ Q = sin ⍜ Var var Abvar 107 Apparent power VA VA = El Volt-ampere VA Power factor pf pf = W/VA; pf = W/(W + jQ) 1 ␲ Ω 9 Reactance, inductive XL XL = 2 fL Ohm Abohm 10 ␲ Ω 9 Reactance, capacitive XC XC = 1/(2 fC) Ohm Abohm 10 Ω 9 Impedance Z Z = E/I Z = R + j(XL - XC) Ohm Abohm 10 Conductance G G = R/Z2 Siemens S Abmho 10-9 B B = X/Z2 Siemens S Abmho 10-9 Y Y =I/E; Y = G + jB Siemens S Abmho 10-9 Frequency f f = 1/T Hz Cps Hz 1 Period T T = 1/f s Second 1 T L/R; RC Second s Second 1 Angular velocity ωω= 2πf /second /s Radians/second 1

*1 Abfarad (EMU Units) = 9 X 10-20 stat farads (ESU units).

Reproduced with Permission from McGraw-Hill, Marks’ Standard Handbook for Mechanical Engineers, 8th ed. Authors: Baumeister, et al. Copyright 1987

Z-264 One Drive | Stamford, CT 06907 | 1-888-TC-OMEGA (1-888-826-6342) | [email protected] www.omega.com

UNITED KINGDOM www. omega.co.uk Manchester, England 0800-488-488

UNITED STATES FRANCE www.omega.com www.omega.fr 1-800-TC-OMEGA Guyancourt, France Stamford, CT. 088-466-342

CANADA CZECH REPUBLIC www.omega.ca www.omegaeng.cz Laval(Quebec) Karviná, Czech Republic 1-800-TC-OMEGA 596-311-899

GERMANY BENELUX www.omega. www.omega.nl Deckenpfronn, Germany Amstelveen, NL 0800-8266342 0800-099-33-44

More than 100,000 Products Available!

Temperature Data Acquisition Calibrators, Connectors, General Test and Auto-Dialers and Alarm Monitoring Systems, Instruments, Glass Bulb Thermometers, Handheld Instruments Communication Products and Converters, Data for Temperature Measurement, Ice Point References, Acquisition and Analysis Software, Data Loggers Indicating Labels, Crayons, Cements and Lacquers, Infrared Plug-in Cards, Signal Conditioners, USB, RS232, RS485 Temperature Measurement Instruments, Recorders Relative and Port Data Acquisition Systems, Wireless Humidity Measurement Instruments, RTD Probes, Elements Transmitters and Receivers and Assemblies, Temperature & Process Meters, Timers and Counters, Temperature and Process Controllers and Power Pressure, Strain and Force Switching Devices, Elements, Probes and Displacement Transducers, Dynamic Measurement Assemblies,Thermocouples Thermowells and Head and Well Force Sensors, Instrumentation for Pressure and Strain Assemblies, Transmitters, Wire , Load Cells, Pressure Gauges, Pressure Flow and Level Reference Section, Pressure Switches, Pressure Transducers, Air Velocity Indicators, Doppler Flowmeters, Level Proximity Transducers, Regulators, Measurement, Magnetic Flowmeters, Mass Flowmeters, Strain Gages, Torque Transducers, Valves Pitot Tubes, Pumps, Rotameters, Turbine and Paddle Wheel Flowmeters, Ultrasonic Flowmeters, Valves, Variable Area Heaters Flowmeters, Vortex Shedding Flowmeters Band Heaters, Cartridge Heaters, Circulation Heaters, Comfort Heaters, Controllers, Meters and Switching pH and Conductivity Devices, Flexible Heaters, General Test and Measurement Conductivity Instrumentation, Dissolved Oxygen Instruments, Heater Hook-up Wire, Heating Cable Instrumentation, Environmental Instrumentation, pH Systems, Immersion Heaters, Process Air and Duct, Electrodes and Instruments, Water and Soil Analysis Heaters, Radiant Heaters, Strip Heaters, Tubular Heaters Instrumentation