. 1
R Rn
Capacitance: .....
1
L Ln
Equivalent resistance parallel connected resistance
R R2
R1 R2
Mutual capacity (C)
• coaxial cable =
r 103
(nF/km)
18 ln
• parallel core =
r 103
(nF/km)
36 ln
• shielded twisted pair
CB =
r 103
(nF/km)
36 ln
Da Outer diameter over insulation
Ds diameter over shield
d diameter conductor
a distance mid mid both
conductors
= dielectric constant
Da
d
Da
d
2a
d
(Da2 a2)
(Da2 a2)
Di
d
2a
d
Di
d
(Da2 a2)
(Da2 a2)
2a
d
1
10
FORMULAS ELECTROTECHNIC AND ELECTRONIC
.. Cn
Inductance:
1
=
1
+
1
+
1
+ .. resistance
m mm2
mm2
m
Copper 58,00 0,01724
Aluminium 33,00 0,0303
Silver 62,00 0,0161
Iron 7,70 0,1299
Constantan 2,00 0,50
Serial connection
Resistance: .... Rn
Capacitance:
1
=
1
+
1
+
1
+ . Ln
Parallel connection
Resistance: .. +
1
C Cn
Inductance: .1144
Cross-section for single wire round
q D2
or D2
0,7854
4
Cross-section for bunched wire
q d2
n d2
0,7854 n
4
Diameter for
single wires cross-section
D =
q or
1,2732
Diameter for bunched wires
D 1,34 d
q cross-section (mm2
)
D conductor diameter (mm)
d single wire diameter (mm)
n number wires
Conductor Resistance
R oder l
q q
R Schleife oder p
q q
R Electrical direct-current resistant (Ohm)
R Schleife Resistance complete circuit
q cross-section (mm2
or mm)
(Kappa) Conductivity
(Rho) Speci resistance )
I Conductor length (m)
Ohm‘s Law
The current intensity (I) proportional voltage (U) and inversely
proportional resistance (R)
I R
R l
I current intensity (Amps A)
R electrical resistance )
U electrical voltage (V)
Conductance
G 1
R M
S (Siemens) reziprocal value resistance
is used conductance
1 Siemens 1/Ohm
G electrical conductance
Capacitance
• Single core against earth
CB =
r 103
(nF/km pF/m)
18 ln
• Unshielded symmetrical twisted pair
CB =
r 103
(nF/km pF/m)
36 ln
• Coaxial pair
CB =
r 103
(nF/km pF/m)
18 ln
• Shielded symmetrical twistet pair
CB =
r 103
(nF/km pF/m)
36 ln
Di outer diameter over single core (mm)
Da outer diameter multicores (mm)
d conductor diamete (mm)
a distance between two conductors mid mid both conductors
Inductance parallel cores
at low frequencies
L 0,4 (In
Da
+ 0,25) mH/km
r
at high frequencies
L 0,4 (In
Da
+ mH/km
r
,QGXFWDQFHRIFRD[LDOFDEOH
at high frequencies
L 0,2 (In
Da
+ mH/km
r
Da distance between two conductors mid mid both conductors
r radius conductor
r dielectric constant
Impedance (Z)
for coaxial cable =
60
In
D
( d
D diameter over insulation
d conductor diameter
for communication cable
at low frequencies =
R
( tan 45°
C
at high frequencies =
L
( )
C
R Resistance /km)
L Inductance (mH/km)
C Capacitance (nF/km)
= f
Wave length =
v
f
= wave length
V propagation velocity
(velocity light: 300 000 km/s)
f frequency
units attenuation Neper (N), decibel (dB) and Bel (B)
1 8,686 dB
1 0,1151 Bel
1 Bel 1,1513 Np
Materials Conductivity Spec.
