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Constants and Standards

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DIELECTRIC CONSTANTS OF MATERIALS

The dielectric constants of most materials vary for different ternperatures and frequencies. Likewise, small differences in the composition of materials will cause differences in the dielectric constants. A list of materials and the approximate range (where available) of their dielectric constants are given in Table 2-1. The values shown are accurate enough for most applications. The dielectric constants of sorne materials (such as quarfz, Styrofoam, and Teflon) do not change appreciably with frequency.

Table 2-1 Dielectric constants of Matrials

 

Material Dielectric
Constants
(Approx.)
 Material Dielectri
Constantc
(Approx.)
 
Air
Amber
Asbestos Fiber
Bakelite (asbestos base)
Bakelite (mica filled)
Barium Titanote
Beeswax
Cambric (varnished)
Carbon Tetrachloride
Colluloid
Collulose Acetate
Durite
Ebonite
Epoxy Resin
Ethyl Alcohol (obsolute)
Fiber
Formica
Glass (electrical)
Glass (photogrophic)
Glass (Pyrex)
Glass (window)
Gutta Percha
Isolantite
Lucite
Mico (olectrical)
Mica (cloor Indio)
Mica (filled phenolic)
Micaglass (titanium dioxide)
Micarta
Mycolex
Neoprene
1.0
2.6-2.7
3.1-4.8
5.0-22
4,5-4.8
100-1250
2.4-2.8
4.0
2.17
4.0
2.9-4.5
4.7-5.1
2.7
3.4-3.7
6.5-25
.0
3.6-6.0
3.8-14.5
7.5
4,6-5.0
7.6
2.4-2.6
6.1
2.5
4.0-9.0
7.5
4.2-5.2
9.0-9.3
3.2-5.5
7.3-9.3
4.0-6.7
  Nylon
Poper (dry)
Paper (paraffin coated)
Paraffin (solid)
Plexiglas
Polycorbonate
Polyethylene
Polyimide
Polystyrene
Porcelain (dry process)
Porcelain (wet process)
Quartz
Quartz (fused)
Rubber (hard)
Ruby Mica
Selenium (amorphous)
Shellac (natural)
Silicone (glass) (molding)
Silicone (glass) (laminate)
Slate
Soil (dry)
Steatite (ceramic)
Steatite (low loss)
Styrofoam
TefIon
Titanium Dioxide
Vaseline
Vinylite
Water (distilled)
Waxes, Mineral
Wood (dry)
3.4-22.4
1.5-3.0
2.5-4.0
2.0-3.0
2.6-3.5
2.9-3.2
2.5
3.4-3.5
2.4-3.0
5.0-6.5
5.8-6.5
5.0
3.78
2.0-4.0
5.4
6.0
2.9-3.9
3.2-4.7
3.7-4.3
7.0
2.4-2.9
5.2-6.3
4.4
1.03
2.1
l00
2.16
2.7-7.5
34-78
2.2-2.3
1.4-2.9

METRIC SYSTEM

The international system of units developed by the General Conference on Weights and Measures (abbreviated CGPM), commonly called the metric system, is the basis for a worldwide

Table 2-2. SI Base and Supplementary Units
Quantity Unit Symbol
length
mass
time
electric current
thermodynamic temperature
amount of substance
luminous intensity
plane angle
solid angle
meter
kilograrn
second
ampere
kelvin *
mole
candela
radiant
steradiont
m
kg
s
A
K
mol
cd
rad
sr
* The degree Celsius is also used for expressing temperature. Supplementory units.

Table 2-3. SI Derived Units With Special Names
QuantityUnitSymboll Formula
frequency (of a periodic phenomenon)
force
pressure, stress
energy, work, quantity of heat
power, radiant flux
quantity of electricity electric charge
electric potential, potential difference, electromotive force
capacitance
electric resistance
concluctance
magnetic flux
magnetic flux density
incluctance
luminous flux
illuminance
activity (of radionuclides)
obsorbed close
hertz
newton
pascal
joule
watt
coulomb
volt
farad
ohm
siemens
weber
tesla
henry
lumen
lux
becquerel
gray
Hz
N
Pa
J
W
C
V
F
W
S
Wb
T
H
Im
Ix
Bq
Gy
I/s
kg'm/s2
N/m2
N*m
J/s
A*s
W/A
C/V
V/A
AN
V*s
Wb/m2
Wb/A
cd*sr
Im/m2
I/s
J/kg

standardization of units. This International System of Units (abbreviated SI) is divided into three classes-base units, supplementary units; and derived units.

Units and Symbols

The seven base units and the two supplementary units with their symbols are given in Table 2-2. Derived units are formed by combining base units, supplementary units and other derived units. Certain derived units have special names and symbols. These units, their symbols and formulas, are given in Table 2-3. Other common derived units,- and their symbols, are given in Table 2-4.

Table 2-4. Common SI Derived Units
QuantityUnit Symbol
acceleration
angular acceleration
angular velocity
area
concentration (of amount of substance)
current density
density, mass
electric charge density
electric field strength
electric flux density
energy density
entropy
heat capacity
heat flux density irradiance
luminance
magnetic field strength
molar energy
molar entropy
molar heat capacity
moment of force
permeability
permittivity
radiance
radiant intensity
specific heat capacity
specific energy
special entropy
specific volume
surface tension
thermal conductivity
velocity
viscosity, dynamic
viscosity, kinernatic
volume
wovenumber
meter per second squored
radian per second squared
radion per second
square meter
mole per cubic meter
ampere per square meter
kilogram per cubic meter
coulomb per cubic meter
volt per meter
coulomb per square meter
joule per cubic meter
joule per kelvin
joule per kelvin
watt per square meter
candela per square meter
ampere per meter
joule per mole
joule per mole kelvin
joule per mole kelvin
newton meter
henry per meter
farad per meter
watt per square meter steradian
watt per steradion
joule per kilogram kelvin
joule per kilogrom
joule per kilogram kelvin
cubic meter per kilogrom
newton per meter
watt per meter kelvin
meter per second
poscal second
square meter per second
cubic meter
l per meter
m/s2
rad/s2
rad/s
m2
mol/m3
A/m2
kg/m3
C/m3
V/m
C/m2
J/m3
J/K
J/K
W/M2
cd/m2
A/m
J/mol
J/(mol*K)
J/(mol*K)
N-m
H/m
F/m
W/(m2 -sr)
W/sr
J/(kg*K)
J/kg
J/(kg*K)
M3/kg
N/m
W/(m*K)
m/s
Pa*s
m2/s
m 3
I/m

Some units, not part of SI are so widely used they are impractical to abandon. These units Listed in Table 2-5) are acceptable for continued uses.

Table 2-5 Units in Use With SI
Quantity Unit Symbol Value
Time




Plane angle


volume
Mass
Area (land)
minute
hour
day
week, month,
year
degree
minute
second
liter
metric ton
hectare
min
h
d


°
'
"
L*
t
ha
1 min = 60 s
1 h = 60 min = 3600 s
1 d = 24h = 86,400 s


l = (p/I 80) rad
1' = (1/60)° = (p 10800) rad
1" = (1/60)' = (p/648 000) rad
1 L = 11 dml = 10-3 M3
1 t = 103 kg
1 ha = 104 M2
*The international symbol for liter is the lowercase 'l', which can be confused with the number "1." Therefore the symbol "L' or spelling out the term liter is advisable.

Prefixes

The sixteen prefixes in Table 2-6 are used to form multiples and submultiples of the SI units. The use of more than one prefix is to be avoided (e.g. pico instead of micromicro and giga instead of kilomega). The preferred pronunciation of the terms is also included in the table. The accent is on the first syllable of each prefix.

Table 2-6. Metric Prefixes
Muftiplication Factor Prefix Abbreviation Pronunciation
1018
1015
1012
109
106
103
102
10
10-1
10-2
10-1
10-6
10-9
10-12
10-15
10-16
exa
peta
tera
giga
mega
kilo
hecto
deka
deci
centi
milli
micro
nano
pico
fernto
atto
E
P
T
G
M
k
h*
da*
d*
C*
m
µ
n
p
f
a
ex'a (a as in a bout)
as in petal
as in terrace
jig'a (a as in a bout)
as in mega phone
as in kilowatt
heck' toe
deck'a (a as in a bout)
as in decimal
as in sentiment
as in military
as in microphone
nan'oh (an as in ant)
peek'oh
fern'toe (fem as in feminine)
as in anatomy
.The use 0f hecto, deka, deci, and centi should be avoided for SI unit multiples except for area and volume, and the nontechnical use of centimeter for body and clothing measurements.

Updated February 1999