Thevenin Equivalent Circuit: using open/short circuit method

In summary, the conversation discusses the process of finding the Thevenin voltage and short-circuit current for a circuit with a known Thevenin voltage and an unknown resistor. The user uses node voltage to find the Thevenin voltage and attempts to use source transformation to find the short-circuit current, but later realizes it can be found using KCL at the terminal node.
  • #1
november1992
120
0

Homework Statement


http://i.imgur.com/fSRqw.png


Homework Equations


[itex]V_{th}[/itex] = [itex]V_{oc}[/itex]


The Attempt at a Solution



I got the thevenin voltage by using node voltage

[itex]\frac{V2-40}{5}[/itex] - [itex]\frac{80+2V2}{5}[/itex] -8 + V2 = 0

([itex]\frac{1}{5}[/itex] + [itex]\frac{2}{5}[/itex] + 1)V2 = 32

[itex]\frac{8}{5}[/itex]V2 = 32
V2 = 20V = Vth

but I don't know how to setup the equation to find the short-circuit current. Since there's a short circuit, I believe that means no current goes through the 1 ohm resistor. I tried using a source transformation, but I got 28A as the current. Since Rth is 0.625, then the current has to be 32A.

http://i.imgur.com/6Twjp.png
 
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  • #2
With the short in place you know what the potential at terminal a is and therefore the potential across the resistor, thus handing you ix. Do KCL for the terminal 'a' node.
 
  • #3
I wrote the current of the 1 ohm resistor in terms of v and r, I just forgot that it was in parallel with node 2.
 

FAQ: Thevenin Equivalent Circuit: using open/short circuit method

What is Thevenin's Theorem and why is it important?

Thevenin's Theorem is a technique used in electrical circuit analysis to simplify complex circuits into a single equivalent circuit. It states that any linear electrical network can be replaced by an equivalent circuit consisting of a voltage source in series with a resistor. This is important because it allows for easier analysis and understanding of complex circuits.

What is the process for finding the Thevenin equivalent circuit using the open circuit method?

The process involves removing the load resistor from the original circuit and calculating the open circuit voltage between the two terminals. Then, the equivalent resistance is found by shorting all voltage sources and calculating the total resistance between the two terminals. The Thevenin equivalent circuit is then constructed using the open circuit voltage and the equivalent resistance.

How does the Thevenin equivalent circuit help in circuit analysis?

Thevenin's Theorem simplifies complex circuits into a single equivalent circuit, making it easier to analyze and understand the behavior of the circuit. It also allows for quick and accurate calculations of voltage, current, and power in the circuit.

Can the Thevenin equivalent circuit be used for non-linear circuits?

No, Thevenin's Theorem is only applicable to linear circuits. Non-linear circuits do not obey Ohm's Law, which is a fundamental assumption in the application of Thevenin's Theorem.

Are there any limitations to using the Thevenin equivalent circuit?

Yes, Thevenin's Theorem is only applicable to linear circuits and cannot be used for circuits with non-linear elements such as diodes or transistors. It also assumes that the circuit is in a steady-state condition and does not take into account transient behavior.

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