# Thevenin equivalents

Thévenin’s theorem

• The equivalent voltage Vth is the voltage obtained at terminals A–B of the network with terminals A–B open circuited.
• The equivalent resistance Rth is the resistance that the circuit between terminals A and B would have if all ideal voltage sources in the circuit were replaced by a short circuit and all ideal current sources were replaced by an open circuit.

Thevenin’s Theorem is a technique that allows us to convert a circuit (often a complex circuit) into a simple equivalent circuit. The equivalent circuit consists of a constant voltage source and a single series resistor called the Thevenin voltage and Thevenin resistance, respectively.

## What does Thevenin’s equivalent circuit consists?

The Thevenin’s equivalent circuit consists of a series resistance of 6.67 Ω and a voltage source of 13.33 V . The current flowing in the circuit is calculated using the formula below: Thevenin’s theorem can be applied to both AC and DC circuits.

## What are the advantages of using Thevenin theorem?

Thevenin’s theorem can be used as a circuit analysis method and is especially useful if the load is to take a series of different values. It is not as powerful as Mesh or Nodal analysis in larger networks because the use of Mesh or Nodal analysis is usually necessary for any Thevenin exercise, so it might well be used from the start.

## How to use Thevenin theorem on circuit?

• Identify the load resistance value of RL
• Remove the load resistance and calculate the open circuit potential across the two open ends. …
• Again remove the load resistance and replace all active sources with their internal resistance and find Rth – If we find the equivalent resistance then there is no need of …

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## How to solve Thevenin circuits?

Thevenin’s Theorem Solved Example. Find V TH, R TH and the load current I L flowing through and load voltage across the load resistor in the circuit below using Thevenin’s Theorem.. Solution: Step 1: Remove the 5 kΩ from the circuit. Step 2: Measure the open-circuit voltage.This will give you the Thevenin’s voltage (V TH).. Step 3: We calculate Thevenin’s voltage by determining the …

## How do you find Thevenin equivalents?

To calculate the Thevenin equivalent voltage, the load impedance is open-circuited. And find an open-circuit voltage across the load terminals. Thevenin equivalent voltage (Veq) is equal to the open-circuit voltage measured across two terminals of load.

## What is the Thevenin equivalent resistance?

Thevenin’s Theorem. Thevenin theorem is an analytical method used to change a complex circuit into a simple equivalent circuit consisting of a single resistance in series with a source voltage.

## What are Thevenin and Norton equivalents?

hévenin’s and Norton’s equivalent are circuit simplification techniques that focus on terminal behavior. This Theorem says that any circuit with a voltage source and a network of resistors can be transformed into one voltage source and one resistor.

## What is Thevenin’s Theorem formula?

Any combination of batteries and resistances with two terminals can be replaced by a single voltage source e and a single series resistor r. The value of e is the open circuit voltage at the terminals, and the value of r is e divided by the current with the terminals short circuited.

## How do you calculate RTH and VTH?

1:5112:19Thevenin’s circuit, finding Vth and Rth network theory – GATE and IESYouTubeStart of suggested clipEnd of suggested clipYou have the function relating il with the I th and RL + v th. So you don’t have to worry about theMoreYou have the function relating il with the I th and RL + v th. So you don’t have to worry about the changed value of RL. You just have to put the new value and you will get the new value of IL. If.

## What is VTH in Thevenin theorem?

Thévenin’s theorem is a process by which a complex circuit is reduced to an equivalent circuit consisting of a single voltage source (VTH) in series with a single resistance (RTH) and a load resistance (RL).

## Why is Thevenin theorem used?

Thevenin’s Theorem provides an easy method for analyzing power circuits, which typically has a load that changes value during the analysis process. This theorem provides an efficient way to calculate the voltage and current flowing across a load without having to recalculate your entire circuit over again.

## What is Norton’s equivalent circuit?

The Norton equivalent circuit is used to represent any network of linear sources and impedances at a given frequency. Norton’s theorem and its dual, Thévenin’s theorem, are widely used for circuit analysis simplification and to study circuit’s initial-condition and steady-state response.

## What is Norton’s theorem formula?

Any collection of batteries and resistances with two terminals is electrically equivalent to an ideal current source i in parallel with a single resistor r. The value of r is the same as that in the Thevenin equivalent and the current i can be found by dividing the open circuit voltage by r.

## How do you find Thevenin and Norton equivalent circuits?

Thevenin and Norton’s resistances are equal. Thevenin voltage is equal to Norton’s current times Norton resistance. Norton current is equal to Thevenin voltage divided by Thevenin resistance.

## How is Thevenin resistance measured?

Find the Thevenin resistance by removing all power sources in the original circuit (voltage sources shorted and current sources open) and calculating total resistance between the open connection points. Draw the Thevenin equivalent circuit, with the Thevenin voltage source in series with the Thevenin resistance.

## What is VTH and RTH?

The Thevenin voltage VTH is defined as the open-circuit voltage between nodes a and b. RTH is the total resistance appearing between a and b when all sources are deactivated.

## How do you solve for Thevenin resistance?

0:009:22Thevenin’s Theorem – Circuit Analysis – YouTubeYouTubeStart of suggested clipEnd of suggested clipIn this video we’re going to talk about how to use thevenin’s theorem to calculate the current thatMoreIn this video we’re going to talk about how to use thevenin’s theorem to calculate the current that is flowing through the load resistor rl. So what we need to do is we need to determine the thevenin

## How do you find equivalent resistance?

(d) Using Ohm’s law (V2=I2R2), the power dissipated by the resistor can also be found using P2=I22R2=V22R2. To find the equivalent resistance of the circuit, notice that the parallel connection of R2 and R3 is in series with R1, so the equivalent resistance is Req=R1+(1R2+1R3)−1=1.00Ω+(16.00Ω+113.00Ω)−1=5.10Ω.

## How to find thevenin equivalent?

Finding Thevenin Equivalents in Practice 1 Find V th by measuring the open circuit voltage with a multimeter. 2 Find R th by connecting a current meter to the two terminals and dividing V th by the measured current (called a short-circuit current). Note that this isn’t the safest method and should never be used in practice! A safer and more proper method for finding R th is outlined in Lab 3. That is, find a load resistance that produces a noticeable drop in the load voltage. Then find R th by applying the voltage divider formula.

## Why is finding the Thevenin equivalent more difficult?

In theory, finding the Thevenin equivalent is more difficult because we can’t rely on lab equipment to do the work for us. On paper, the Thevenin equivalent resistance (R th) is easier to find. 1. If there is a load, remove it – Remember that Thevenin’s theorem applies to two terminal circuits.

## What is Thevenin’s theorem?

Thevenin’s theorem states that a two terminal circuit containing voltage sources, current sources, and resistors can be modeled as a voltage source in series with a resistor. The benefit of using a Thevenin equivalent is that it makes analyzing how a circuit interacts with other circuits a much simpler process.

## Is Thevenin’s equivalent fun?

See, Thevenin’s Equivalent is a lot of fun! Get good at this and you have mastered quite a few important engineering concepts! Thanks to Ryan Eatinger (reatinge@ksu.edu) for contribution of this lesson.

## How to find the Thevenin equivalent voltage?

4. To find the Thevenin equivalent voltage, we put the voltage source back in and find the voltage across the still open spot where we had the resistor. We were able to simplify the circuit by finding the equivalent parallel resistance of the 200 and 300 ohm resistors, and then we noticed that the voltage across those resistors is actually the Thevenin Voltage. With some simple Ohm’s Law, we calculate it out to 5.45V. ( 1)

## What does Thevenin do?

What Thevenin’s does is identify the load that you care about, and simplify or reduce everything else. Multiple sources and resistors will be converted into a single voltage source and series resistor. If you need to iterate or vary your load, this makes it much easier to do the calculations.

## How to find R Th?

Find R Th by shorting all voltage sources and by open circuiting all the current sources and then see what the resistance looks like from the point of view of the nodes where the load resistor was located.

## Is Thevenin’s equivalent circuit easy to create?

And that’s it! Thevenin’s Equivalent Circuits are very easy to create and the process is simple, you just need to remember the steps. Next, we’ll learn about Norton’s Theorem, which is related but slightly different.

## How to calculate Thevenin’s equivalent circuit?

Steps to calculate Thevenin’s equivalent circuit. 1 Remove the load resistance. 2 After short circuiting all the voltage sources and open circuiting all current sources, find the equivalent resistance (R th) of the circuit, seeing from the load end. 3 Now, find V th by usual circuit analysis. 4 Draw Thevenin’s equivalent circuit with V th, R th and load. From this circuit we can calculate I L for different values of load resistance.

## Why is Thevenin’s theorem important?

Thevenin’s theorem is very important in circuit analysis, power system analysis, short circuit calculations and is a key tool for circuit design. Thevenin’s circuit is a simplified form of a large circuit containing multiple power sources and resistances.

## What is the difference between a V TH and a R TH?

Simply, Thevenin’s theorem states that any linear network with several power sources, resistances and a variable load can be represented in a much simpler circuit containing a single voltage source (V TH ) (known as Thevenin’s equivalent voltage) in series with a resistance (R TH) (known as Thevenin’s equivalent resistance) and the variable load, where V TH is the open-circuit voltage at the terminals of the load and R TH is the equivalent resistance measured across the terminals while independent sources are turned off. See the below figure for better understanding.

## Does Thevenin have an open circuit?

While calculating the thevenin’s equivalent resistance, all voltage sources must be turned off, meaning it acts like a short circuit and all current sources act like an open circuit, as shown in the figure below:

## What is the voltage of the Thevenin?

8 kΩ is parallel to the 4 kΩ, so the same voltage will appear across the 8 kΩ resistors too. Therefore, 12 V will appear across the AB terminals. Therefore, the Thevenin’s voltage, V TH = 12 V.

## How to calculate Thevenin voltage?

This will give you the Thevenin’s voltage (V TH ). Step 3: We calculate Thevenin’s voltage by determining the current that flows through 12 kΩ and 4 kΩ resistors.

## What is Thevenin’s theorem?

Thevenin’s theorem states that it is possible to simplify any linear circuit, irrespective of how complex it is, to an equivalent circuit with a single voltage source and a series resistance.

## Which theorem is used to calculate current and voltage?

Thevenin’s Theorem. Most commonly, we use Ohm’s law, Kirchoff’s law to solve complex electrical circuits, but we must also be aware that there are many circuit analysis theorems from which we can calculate the current and voltage at any given point in a circuit. Among the various circuit theorems, Thevenin’s theorem is most commonly used.

## Is Thevenin’s theorem applicable to nonlinear circuits?

No, Thevenin’s Theorem is not applicable to non-linear circuits.

## Is Thevenin equivalent the same as real system?

The power dissipation of the Thevenin equivalent is not identical to the power dissipation of the real system.

## Who discovered the second equivalency?

In one of those coincidences that seem to be common in science and technology, in 1926, both Hans Ferdinand Mayer and Edward Lawry Norton, each independently discovered a second equivalency, in which any circuit with a Thévenin equivalent can also be described by a single current source in parallel with a single resistor. For some reason, this equivalent is universally known as a Norton equivalent circuit. Herr Mayer seems to have been entirely forgotten, which is sad since he has a very interesting life story outside of engineering.

## Which theorem states that a circuit has a single voltage source and a single series resistor?

FIGURE 1. The Thévenin equivalency theorem says that we can define a circuit with a single voltage source V T and a single series resistor R T (at right) that has identical behavior as far as the load is concerned, for any combination of sources and resistances such as the example circuit on the left.

## Overview As originally stated in terms of direct-current resistive circuits only, Thévenin’s theorem states that “For any linear electrical network containing only voltage sources, current sources and resistances can be replaced at terminals A–B by an equivalent combination of a voltage source Vth in a series connection with a resistance Rth.”

## Calculating the Thévenin equivalent The equivalent circuit is a voltage source with voltage VTh in series with a resistance RTh.
The Thévenin-equivalent voltage VTh is the open-circuit voltage at the output terminals of the original circuit. When calculating a Thévenin-equivalent voltage, the voltage divider principle is often useful, by declaring one terminal to be Vou…

## Conversion to a Norton equivalent A Norton equivalent circuit is related to the Thévenin equivalent by

## Practical limitations

• Many circuits are only linear over a certain range of values, thus the Thévenin equivalent is valid only within this linear range.
• The Thévenin equivalent has an equivalent I–V characteristic only from the point of view of the load.
The power dissipation of the Thévenin equivalent is not necessarily identical to the power dissipation of the real system. However, the power dissipated by an external resistor bet…

• Many circuits are only linear over a certain range of values, thus the Thévenin equivalent is valid only within this linear range.
• The Thévenin equivalent has an equivalent I–V characteristic only from the point of view of the load.
• The power dissipation of the Thévenin equivalent is not necessarily identical to the power dissipation of the real system. However, the power dissipated by an external resistor between the two output terminals is the same regardless of how the inter…

## A proof of the theorem

The proof involves two steps. The first step is to use superposition theorem to construct a solution. Then, uniqueness theorem is employed to show that the obtained solution is unique. It is noted that the second step is usually implied in literature.
By using superposition of specific configurations, it can be shown that for any linear “black box” circuit which contains voltage sources and resistors, its voltage is a linear function of the corres…

## In three-phase circuits

In 1933, A. T. Starr published a generalization of Thévenin’s theorem in an article of the magazine Institute of Electrical Engineers Journal, titled A New Theorem for Active Networks, which states that any three-terminal active linear network can be substituted by three voltage sources with corresponding impedances, connected in wye or in delta.

• Millman’s theorem
• Source transformation
• Superposition theorem
• Norton’s theorem
• Maximum power transfer theorem

• Wenner, Frank (1926). “A principle governing the distribution of current in systems of linear conductors”. Proceedings of the Physical Society. Washington, D.C.: Bureau of Standards. 39 (1): 124–144. Bibcode:1926PPS….39..124W. doi:10.1088/0959-5309/39/1/311. hdl:2027/mdp.39015086551663. Scientific Paper S531.
• First-Order Filters: Shortcut via Thévenin Equivalent Source — showing on p. 4 complex circuit’s Thévenin’s theorem simplication to first-or…

## Finding Thevenin Equivalents in Practice

• By using the Thevenin equivalent model, the problem was solved without the need to perform a full circuit analysis each time the load changed. However, you must learn how to acquire Thevenin equivalents before you can take advantage of them. In practice, finding the Thevenin equivalent of a circuit is simple. 1. Find Vthby measuring the open circuit voltage with a multimeter. 2. Find Rt…

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## Thevenin Equivalent Resistance

• In theory, finding the Thevenin equivalent is more difficult because we can’t rely on lab equipment to do the work for us. On paper, the Thevenin equivalent resistance (Rth) is easier to find. 1. If there is a load, remove it – Remember that Thevenin’s theorem applies to two terminal circuits. This implies that the circuit is unloaded (see Figure 4). After all, Vthis equal to the open circuit v…

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## Thevenin Equivalent Voltage

• Any of the circuit analysis techniques learned so far can be used to find the Thevenin equivalent voltage (Vth). Voltage dividers, branch currents, node voltage, superposition, and source transformations (the last two will be covered soon) are all legitimate methods for finding Vth. Of the two Thevenin equivalent values, Vthtends to be the harder o…