Equivalent Voltage for Thevenin Equivalent Circuit

In summary: This is the Thevenin voltage and it will be the same no matter what load is connected.In summary, Thevenin's theorem states that the equivalent voltage for the Thevenin equivalent circuit is the open-circuit voltage, which is the potential at the output terminals when the output current is zero. This may seem counterintuitive, but electric potential can exist without current flowing. The Thevenin voltage is determined by considering the potential that the source and network "presents" to the point where a load is connected, and it will be the same regardless of the load connected.
  • #1
Kurushimi
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Homework Statement


This isn't for a class I'm actually taking. Just self study.

I'm reading a book on electronics. When I got to the part about Thevenin's theorem I got a little confused. Specifically, I'm confused about the equivalent voltage for the Thevenin equivalent circuit. It said the equivalent voltage would be the open-circuit voltage, which the book defines as "potential at the output terminals when the output current is zero".

The reason this confuses me is that when I think of the equation V = IR, when you have a 0 current you should have 0 voltage. The book showed an example for calculating the equivalent voltage but they didn't explain how they arrived at their equation, so I figure it's something basic that I'm missing.

The Attempt at a Solution


I went to wikipedia's page on Thevenin's theorem used the concept of a voltage divider to show an example of how to calculate the equivalent voltage. Doing this also yields the equation my book got for its example of calculating equivalent voltage. However, my understanding of a voltage divider relies on the existence of a current through the circuit. Even the proof given the wikipedia page linked uses the assumption of current. So I don't see how it makes sense to apply this concept when calculating equivalent voltage with the assumption that there is no current. How does this make sense?
 
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  • #2
Electric potential can exist without current flowing. Take for example an isolated 10V battery (no connections). There's still a potential difference of 10V between its terminals even with a load connected. This will be true even if the battery is not ideal and has an internal resistance (no current means no drop across the internal resistance).

The idea with the Thevenin voltage for a given source and network is that you first remove any load and consider the potential that the source and network "presents" to the point where a load was (or will be) connected.
 

What is the concept of Equivalent Voltage in Thevenin Equivalent Circuit?

The concept of Equivalent Voltage in Thevenin Equivalent Circuit is a simplified representation of a complex circuit that can be used to analyze its behavior. It is a single voltage source that can replace the original circuit without changing the overall behavior of the circuit.

How is the Equivalent Voltage calculated in a Thevenin Equivalent Circuit?

The Equivalent Voltage in a Thevenin Equivalent Circuit is calculated by open-circuiting the load terminals and measuring the voltage across them. This voltage is the same as the Equivalent Voltage, and it can be found by using Ohm's Law and Kirchhoff's Voltage Law.

What is the significance of Equivalent Voltage in a Thevenin Equivalent Circuit?

The Equivalent Voltage in a Thevenin Equivalent Circuit is significant because it simplifies the analysis of a complex circuit. It allows us to use a single voltage source and a single resistor to represent the behavior of the original circuit, making it easier to calculate currents and voltages.

Can the Equivalent Voltage change in a Thevenin Equivalent Circuit?

Yes, the Equivalent Voltage in a Thevenin Equivalent Circuit can change depending on the load connected to the circuit. As the load resistance changes, the voltage across the load changes, and so does the Equivalent Voltage. However, the Thevenin Equivalent Circuit remains the same.

How is the Thevenin Equivalent Circuit used in practical applications?

The Thevenin Equivalent Circuit is used in practical applications to simplify the analysis of complex circuits. It is also used in the design of electronic circuits, as it allows for easier calculations of currents and voltages. Additionally, it is used in troubleshooting and testing circuits to determine their behavior and performance.

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