DC CIRCUIT ANALYSIS
Basic DC Theory
Clear the fraction so that we have a common denominator:
4VN
3
(60
VN)
6
(20
VN)
4VN
180
3VN
120
6VN
13VN
300
VN
23.077
Third, find all voltage drops and currents.
V1
VA
VN
60
23.077
36.923 Volts
V2
VN
23.077 Volts
V3
VB
VN
20
23.077
3.077 Volts
The negative value for V3 shows that the current flow through R3 is opposite that which was
assumed and that the polarity across R3 is reversed.
I1
V1
R1
36.923 V
8W
4.65 amps
I2
V3
R3
3.077 V
4W
0.769 amps
I3
V2
R2
23.077 V
6W
3.846 amps
The negative value for I3 shows that the current flow through R3 is opposite that which was
assumed.
Series-Parallel Circuit Analysis
When solving for voltage, current, and resistance in a series-parallel circuit, follow the rules
which apply to the series part of the circuit, and follow the rules which apply to the parallel part
of the circuit. Solving these circuits can be simplified by reducing the circuit to a single
equivalent resistance circuit, and redrawing the circuit in simplified form. The circuit is then
called an equivalent circuit (Figure 46).
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