Thevenin Equivalent of AC RLC Circuit w/ Dependent Voltage

Click For Summary
SUMMARY

The discussion focuses on finding the Thevenin equivalent voltage (Vth) and impedance (Zth) of an AC RLC circuit with dependent voltage sources at a frequency of 2 kHz. The user initially attempted nodal analysis, concluding that Vth is 0V due to the absence of independent sources. The recommended method involves adding a 2 kHz current source at the load terminals and applying nodal analysis to solve for the voltage across the terminals, which is then divided by the current source to determine Zth. This approach successfully yielded the desired results.

PREREQUISITES
  • Understanding of Thevenin's theorem in AC circuits
  • Familiarity with nodal analysis techniques
  • Knowledge of complex impedance calculations for inductors and capacitors
  • Proficiency in AC circuit analysis at 2 kHz frequency
NEXT STEPS
  • Learn about Thevenin's theorem applications in AC circuits
  • Study complex impedance calculations for RLC circuits
  • Explore advanced nodal analysis techniques for circuits with dependent sources
  • Investigate the use of phasors in AC circuit analysis
USEFUL FOR

Electrical engineering students, circuit designers, and anyone involved in AC circuit analysis and Thevenin equivalent calculations.

YellowBelliedMarmot
Messages
10
Reaction score
1

Homework Statement


Diagram.png

Find Vth and Zth.
frequency = 2kHz

Homework Equations


w = 2 * (pi) * f
ZL = j w L
ZC = -j / (w * C)
V = I*Z
ZR = R

The Attempt at a Solution


At first I tried using nodal analysis which I receive the value V = 0 v. I believe this is because this circuit only has dependent voltage sources. Therefore, the Vth is just 0 v.

10mH ---> j125.7
1uF ---> -j79.6
100 ohms ---> 100
w = 2*(pi)*2000 = 12566.37

Essentially, I am stuck. I have some theories as to what I can do though. I remember from DC circuit analysis that we can either add a 1v or a 1A (the number is arbitrary) source between terminals a and b, but I'm not sure what to do beyond that. Could I add a 1A (i.e. 1*cos(wt)) between the terminals, and then do nodal analysis? Then after that, would I take that voltage and divide it by the 1A (1cos(wt)) AC source to get the Zth? And as I mentioned above, wouldn't the thevenin equivalent of this circuit not even have a Vth since there's no independent sources?
 
Physics news on Phys.org
A zero value for the Thevenin voltage is reasonable; zero is a perfectly good real number.

For the impedance, your suggested approach has merit: add a generic 2 kHz current source ##I## at the load terminals. Use nodal analysis again leaving that current source as a variable and solve for ##v_{ab}##. Note that the desired impedance is ##v_{ab} / I##.
 
  • Like
Likes   Reactions: YellowBelliedMarmot
gneill said:
A zero value for the Thevenin voltage is reasonable; zero is a perfectly good real number.

For the impedance, your suggested approach has merit: add a generic 2 kHz current source ##I## at the load terminals. Use nodal analysis again leaving that current source as a variable and solve for ##v_{ab}##. Note that the desired impedance is ##v_{ab} / I##.
I tried it out and it worked! Thanks for your help! All this circuit stuff is starting to really make sense now!
 

Similar threads

  • · Replies 10 ·
Replies
10
Views
4K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 9 ·
Replies
9
Views
6K
  • · Replies 42 ·
2
Replies
42
Views
6K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 17 ·
Replies
17
Views
3K