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Kirchhoff’sfirstlaw-calledcurrentlaw-concernsthenodes(Fig.1.8b),
whatmeans:
I
-
(
I
1
+
I
2
+
I
3
)0
±
ą
nodeC
I
1
+
I
2
+
I
3
-±
I
0
ą
nodeD
(1.11)
n
Generally,thesumofcurrentsinanodeisequaltozero
3
Σ
I
k
±
0
k
±
1
Kirchhoff’ssecondlaw-calledthevoltagelaw-isregardedtotheloops
(Fig.1.8b):
∆
U
1
-∆
U
2
±
0
ą
loopI
∆
U
2
-∆
U
3
±
0
ą
loopII
n
Generally,thevoltagesuminaloopisequaltozero
3
Σ
U
k
±
0
k
±
1
(1.12)
TheΔU
kmeansthevoltagedropcrosskresistor.Thetotalvoltagedropssum
intotheloopisalwaysequaltothevalueofexternalvoltageconnectedtothis
loop.Intheseriesconnectionacurrentvalueisthesameforeachelement.Forthis
reasonthetotalvoltagevalueisasumofthevoltagedrops.
Takingitintoconsiderationandbasingonlinearsuperpositionispossibleto
obtaintherepresentativeequivalent(replacement)Rvalueofconnectedresistors:
Serialconnection:
IR
1
+
IR
2
+
IR
3
+
IR
k
±
IR
BecauseaccordingtoOhm’slawis
∆
U
I
k
±
R
k
R
±Σ
k
n
±
1
R
k
Parallelconnection:
I
1
+
I
2
+
I
3
+
I
k
±
I
∆
U
1
±∆
U
2
±∆
U
3
±∆
U
k
±
U
∆
R
U
1
1
+
∆
R
U
2
2
+
∆
R
U
3
3
+
∆
R
U
k
k
±
U
R
R
1
±Σ
k
n
±
1
R
1
k
Morecomplicatedarethestaranddeltaconnections(Fig.1.9).
(1.13)
(1.14)
17
