Sample Problem
Topic: Thévenin and Norton equivalents
Statement of Problem:
Given the circuit shown in the figure below
Find the Thevenin equivalent w.r.t. terminals a and b.
Solution
In this problem, we have a dependent source. This means we need to solve for the Thevenin equivalent using different methods than when we
did with all independent sources. First, we will determine the V
TH
voltage, which is just the voltage across the 40K
Ω
resistor. This is also V
AB
.
To find the voltage across terminals a and b, we will use the node voltage circuit analysis technique.
We define the terminals as shown.
The node voltage equations are shown below:
°
1
−
4
2000
+
°
1
20000
+
°
1
− °
2
5000
= 0
°
2
− °
1
5000
+
°
2
50000
+
°
2
− °
3
10000
+ 30
°
1
20000
±
= 0
°
3
− °
2
10000
+
°
3
40000
−
30
°
1
20000
±
= 0
Solving this system of equations, we find that
V1 = 24V
V2 = 10V
V3 = 280V = V
TH
Now that we have the “Open circuit” voltage, we use the “short circuit” current method to find the current through the Theven
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 Spring '05
 Unknown
 Electrical Engineering, Thevenin equivalent, Thévenin's theorem

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