Theory - Constants

Theory

Introduction to Electromagnetics

Maxwell's Equations

Near-Field and Far-Field

Transmission Line

Models

Scale modelling

References

Symbols and units

Constants

Mutual Impedance Between Wire Elements

Appendix B - Constants

Table 8 Constants of Free Space

*Constant*	*Symbol*	*Value*
Velocity of light	c	» 3^.10⁸ [m/s]
Permittivity	e ₀	» [F/m]
Permeability	m ₀	[H/m]
Intrinsic impedance	h ₀	» 120p or 377 [W ]

Table 9 Physical Constants

*Constant*	*Symbol*	*Value*
Rest mass of electron	m_e	9.107^.10^-31 [kg]
Charge of electron	-e	-1.602^.10^-19 [C]
Charge-to-mass ratio of electron	-e/m_e	-1.759^.10¹¹ [C/kg]
Radius of electron	R_e	2.81^.10^-15 [m]
Rest mass of proton	m_p	1.673^.10^-27 [kg]

Table 10 Relative Permittivities (average low-frequency values at room temperature)

*Material*	*Value*	*Material*	*Value*
Air	1.0	Plexiglas	3.4
Bakelite	5.0	Polyethylene	2.3
Glass	4-10	Polystyrene	2.6
Mica	6.0	Porcelain	5.7
Oil	2.3	Rubber	2.3-4.0
Paper	2-4	Soil	3-4
Paraffin wax	2.2	Teflon	2.1

Table 11 Relative Permeability's (average low-frequency values at room temperature)

*Material*	*Value*	*Material*	*Value*
*Ferromagnetic:*		*Diamagnetic:*
Nickel	250	Bismuth	0.99983
Cobalt	600	Gold	0.99996
Iron	4000	Silver	0.99998
Mumetal	100000	Copper	0.99999
*Paramagnetic:*
Aluminum	1.000021
Magnesium	1.000012
Palladium	1.00082
Titanium	1.00018

Table 12 Conductivities (average low-frequency values at room temperature)

*Material*	*Value* [S/m]	*Material*	*Value* [S/m]
Silver	6.17^.10⁷	Distilled water	2^.10^-4
Copper	5.80^.10⁷	Dry soil	10^-5
Gold	4.10^.10⁷	Transformer oil	10^-11
Aluminum	3.54^.10⁷	Glass	10^-12
Brass	1.57^.10⁷	Porcelain	2^.10^-13
Bronze	10⁷	Rubber	10^-15
Iron	10⁷	Fused quartz	10^-17

Table 13 Ground Conductivity and Dielectric Constants

*Surface Type*	*Dielectric Constant*	*Conductivity* [*S/m*]	*Comment*
Salt water	81	5.0	Excellent Ground
Fresh water	80	0.001
Pastoral, low hills, rich soil type	20	0.03	Very good
Flat country, marchy, densely wooded	13	0.007
Pastoral, medium hills, few trees	13	0.006
Pastoral, heavy clay soil	13	0.005	Average
Rocky soil, steep hills, mountainous	12	0.002	Poor
Sandy, dry, flat	10	0.002
Cities	5	0.001	Very poor
Cities, high buildings, industrial areas	3	0.001

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EMC of Telecommunication Lines
A Master Thesis from the Fieldbusters © 1997
Joachim Johansson and Urban Lundgren