Electronic Engineers Notebook

Constants and Conversions


Constants

Conductor Constants

Semiconductor Constants

Heat Transfer

Conversions Imperial

Conversions Scientific


Constants

e = 2.71828 18284 59045 23536
p = 3.14159 26535 89793 23846
Velocity of light in vacuum (c) = 2.997925e8 m/s
Boltzmann's constant (k) = 1.38e-23 J/K
Charge of an electron = -1.602e-19 Coulombs
Rest mass of an electron = 9.109e-31 kg
Mass of hydrogen atom = 1.67339e-24 g
Constant of gravitation = 6.673e-8 /cm 3 gm -1 s -2
Earth gravity (G) = 9.806194 m/s 2 at sea level, latitude 45 o
Equatorial radius of the earth = 6378.388km = 3963.34 miles
Polar radius of the earth = 6356.912km = 3949.99 miles
Mean density of the earth = 5.522g/cm 3
Planck constant (h) = 6.6261Js
Velocity of sound = 331.36m/s in dry air at 0 o C (1450ms in water)
Density of water = 1 g/ml at 3.98 o C
Density of dry air = 1.2929g/l at 0 o C, 760mm

Conductor constants

Aluminium

Resistivity (300K) 2.733e-8 ohm.m
Density 2.7Mg/m 3
Melting point 660 o C

Copper

Resistivity (300K) 1.725e-8 ohm.m
Density 8.93Mg/m 3
Melting point 1083 o C

Gold (Au)

Resistivity (300K) 2.271e-8 ohm.m
Density 19.28Mg/m 3
Melting point 1064 o C

Silver (Ag)

Resistivity (300K) 1.629e-8 ohm.m
Density 10.5Mg/m 3
Melting point 962 o C

Semiconductor Constants

 

Germanium

Silicon

Atoms/m 3

4.4e28

5.0e28

Gap energy eV

0.75

1.15

The dependence of semiconductor failure rate on temperature is given by the Arrhenius equation:

E A is the gap energy in eV, k Boltzman's constant

Heat transfer

Aluminium

Thermal conductivity 210 W/(K m)
Specific heat capacity 910 J/(Kg K)
Density 2.7 kg/dm 3
Linear expansion coefficient 2.39e-5 /K

Copper

Thermal conductivity 380 W/(K m)
Specific heat capacity 386 J/(Kg K)
Density 8.96 kg/dm 3
Linear expansion coefficient 1.69e-5 /K

Steel

Thermal conductivity 50 W/(K m)
Specific heat capacity 460 J/(Kg K)
Density 7.8 kg/dm 3
Linear expansion coefficient 1.2e-5 /K

Air

Thermal conductivity 0.0271 W/(K m) @ 40 C
Specific heat capacity 1010 J/(Kg K)
Density 1.128 kg/dm 3 @ 40 C

FR-4 epoxy glass

Thermal conductivity 0.16 W/(K m)
Glass transition temperature 125 degC
Linear expansion coefficient 1.3e-5 to 1.8e-5 /K

Polymide glass

Thermal conductivity 0.35 W/(K m)
Glass transition temperature 250 degC
Linear expansion coefficient 1.2e-5 to 1.6e-5 /K

Copper clad Invar

Thermal conductivity 160 W/(K m) horizontally, 15 to 20W/(K m) vertically
Linear expansion coefficient 5e-6 to 7e-6 /K

Poly aramid fiber

Thermal conductivity 0.15 W/(K m)
Glass transition temperature 250 degC
Linear expansion coefficient 3e-6 to 8e-6 /K

Alumina/ceramic

Thermal conductivity 20 to 45 W/(K m)
Linear expansion coefficient 5e-6 to 7e-6 /K

Conversions Imperial

1 Angstrom = 1e-10m
1 Micron = 1e-6m
1 inch = 1000 'thou'
1 inch = 25.4mm
American Wire Gauge (AWG) = -10 - 20log(diameter_inches)
1 nautical mile = 1852m
1 acre = 0.4047 hectare
1 hectare = 10,000m 2
1 gallon (UK) = 1.201 gallons (US) = 4.546 litres
1 quart (UK) = 1.1365 litres
1 pint = 0.5683 litres
1 fluid ounce = 28.4131 mililitres
1m 3 = 1,000 litres
1 ounce = 28.35g
1 pound = 453.6g
1 stone (UK) = 6.35kg
1 ton (long) = 2240lb = 1016kg
1 ton (short) = 2000lb = 907.2kg
1 tonne (metric) = 1000kg
1 hundredweight = 50.8023kg

Conversions Scientific

1 atmosphere = 1.01325 bars = 33.9 ft of H 2 0 = 76cm of Hg = 101.325 kilonewtons/m 2 (kPa) = 14.696 pounds/inch 2
1 knot = 0.5144m/s = 1.151 miles/hour (US)
1 ergs/s = 1e-7W
1 horsepower (electric) = 746W
1 horsepower (UK) = 745.7W
Celsius to Kelvin K = C + 273.15
Celsius to Fahrenheit F = 32 + 9 C/5
British Thermal Unit = 1055.9J
1 erg = 1e-7J
1 electron Volt = 1.6e-19J


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Last updated July 16, 2000

© 2000 Michael Wells