# Thevenin's Theorem: AC Circuits with Different Frequencies

• Vishera
In summary, the conversation discusses how to calculate the Thevenin equivalent at different frequencies using superposition. The example in the textbook is unrelated and there is confusion about whether to change the frequency of one voltage source or keep them separate. The importance of using the correct units for frequency is also mentioned.
Vishera
My textbook has this excerpt:

I am not sure why it refers to Example 10.6 as that is unrelated. I don't understand to be honest. How can you calculate the Thevenin equivalent at different frequencies? Let us say that you have two voltage source: v1(t)=10cos(5t) and v2(t)=10cos(2t). So how do you calculate the Thevenin equivalent at the first frequency of 5 Hz? Do you change v2's frequency to 5 Hz?

I think they mean when you use superposition, you use the voltage source you're intersted in and short the other one.

You will then have two different circuits, each with it's own voltage source and frequency.

Then when you go to find your open circuit voltage...you will end up with two different open circuit voltages with two different frequencies from two different sources. You cannot add different frequencies together.

One open circuit voltage will contain (5t) and the other open circuit voltage wil contain (2t).
You would never interchange these like you suggested and also the 5 in 5t is not hertz...it's 5 radians per second...

Just my first guess...or 2nd or third...

Last edited:
1 person

## What is Thevenin's Theorem and what does it apply to?

Thevenin's Theorem is a technique used in electrical engineering to simplify complex AC circuits with different frequencies. It can be applied to linear circuits that contain independent and dependent sources, resistors, capacitors, and inductors.

## How does Thevenin's Theorem work?

Thevenin's Theorem states that any linear circuit can be simplified to an equivalent circuit with a single voltage source and a single series resistor. The equivalent voltage source is called the Thevenin voltage and the equivalent resistance is called the Thevenin resistance.

## What is the importance of Thevenin's Theorem?

Thevenin's Theorem is important because it allows engineers to analyze and design complex AC circuits with different frequencies using simple circuit analysis techniques. It also helps in identifying the most critical components in a circuit and predicting its behavior under different conditions.

## Can Thevenin's Theorem be applied to non-linear circuits?

No, Thevenin's Theorem can only be applied to linear circuits. Non-linear circuits contain components whose behavior is not proportional to the applied voltage or current, making it impossible to simplify them using this theorem.

## What are some limitations of Thevenin's Theorem?

Thevenin's Theorem assumes that the circuit is in steady state and that there are no reactive elements present. It also cannot be used to analyze circuits with mutual inductance or when the load is not connected at the output terminals.

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