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Fig.1.6.Exemplarylinearandnonlinearcircuitpassiveelements;staticcharacteristics
Electricalresistivity
p
(rho)iscalledaspecificelectricalresistancethatquan-
titieshowstronglyagivenmaterialopposestheflowofelectriccurrent(material
resistivity).Alowresistivityindicatesamaterialthatreadilyallowsthemovement
ofelectriccharge.Themetalsespeciallyplatinum,gold,copper(commonlyused
asconductors)haveverylowresistivity.Theresistanceofapieceofmetalcon-
ductorisdepictedas:
R
±
p
s
l
ą
p
±
Rs
l
f
|
L
Ω|
m
m
2
1
|
J
ąΩ|
[
m]
(1.6)
where:
l
-lengthofconductor,
s-surfaceofconductorcrosssection.
Electricalconductivity
K
(kappa)(specificconductance)isthereciprocalof
electricresistivity:
K
±
p
1
f
|
L
Ω|
1
m
1
|
J
Generally,inpractice,conductanceGisdefinedas:
(1.7)
G
±
R
1
f
|
L
Ω
1
1
|
J
ąΩ
[
-
1
](siemens)
(1.8)
Theresistanceofmetalconductorsdependsontemperatureasfollows:
where:
R
±
R
20[1
+
Bt
(
-
20C)]
O
(1.9)
R
20-resistanceintemperature20°C,
B
-temperaturecoefficientofresistance[°C-1],
t
-ambienttemperature.
Itmeansthevalueofresistanceisgrowinginlinearwayandtheconductance
isdecreasingiftemperatureisincreasing.
Ionicconductivityisbasedonthechargetransferbyanactiveions.Thisis
typicalforelectrolytesorgases.
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