Find Rth in Thevenen Equivalent Circuit: R1,R2,R3,R4,R5,R6,Vth

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Homework Help Overview

The discussion revolves around finding the Thevenin equivalent circuit parameters, specifically the Thevenin resistance (Rth) and Thevenin voltage (Vth), using a circuit with multiple resistors and voltage sources. The original poster presents a circuit with given values for resistors and voltage sources and seeks confirmation on their approach to calculating Rth.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to analyze the circuit configuration and expresses uncertainty about their interpretation of the arrangement of resistors. They question whether their understanding of R4 being in series with a combination of other resistors is correct.
  • Some participants confirm the calculation of Rth but raise questions about the value of Vth, leading to further exploration of the circuit's behavior under different configurations.
  • One participant discusses replacing the current source with a voltage source and examines the implications for the circuit's loops and current flow, questioning their own calculations along the way.

Discussion Status

The discussion is active, with participants providing feedback on calculations and interpretations. While there is no explicit consensus on the value of Vth, some participants have confirmed the approach to calculating Rth. The conversation reflects a collaborative effort to clarify the circuit analysis without reaching a definitive conclusion.

Contextual Notes

Participants are working under the constraints of homework rules, which may limit the amount of direct assistance they can provide. There is an emphasis on understanding the circuit's behavior rather than simply obtaining answers.

kliker
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[PLAIN]http://img695.imageshack.us/img695/2420/physicsm.jpg

i need to find thevenen equivalent circuit using R5 as load

Ε1=20V, Ε2=10V, R1=6Ω, R2=12Ω, R3= 25Ω, R4=20Ω,
R5=10Ω, R6=5Ω, Ι=0,2Α.

Vth = -5V


but how much is Rth?

i can see that R4 is in series with (R2+R1)||R3 and R6

is this correct?

so the circuit will be

[PLAIN]http://img37.imageshack.us/img37/9126/62188572.jpg

please tell me if I am correct or not i need to know for the exams :(
 
Last edited by a moderator:
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Your calculation for Rth is correct, but I got a different value for Vth.
 
vela said:
Your calculation for Rth is correct, but I got a different value for Vth.

i replaced the current source with a voltage source

we have no current on the second loop

so the voltage source has 5V

hence-E2 + 5V = -5V will be the Vth

am i doing anything wrong?

oh but we have current going through the voltage source

so i have to find the current in the first loop

E1 - E3 - I*(R1+R2+R3) = 0

I = 15/43 = 0.348837209 A

so Vth = -5 + (0.348837209*R3) = -5 + 8.72093023 = 3.72093023 V

is this correct?

so in the shape the + will be on top and - on bottom
 
Last edited:
Yes, that matches what I calculated.
 
thanks a lot for your help :))
 

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