Name: thevenin circuit equivalents
Uploaded: 2024-04-11T12:48:31.000Z
Duration: 1 min 15 s
Channel: JoVE

Thevenin&#39;s theorem states that any linear two-terminal circuit can be replaced by an equivalent circuit with a single voltage source in series with a resistor.
In the absence of load, the voltage across the open terminals will be the Th&#233;venin voltage.
For finding Th&#233;venin resistance, all independent sources are turned off. Then the resistance seen across the terminals is the Th&#233;venin resistance.
If the circuit contains dependent sources, the independent sources are still switched off, but a known test source is applied at the terminals.
From the resulting terminal voltage or current, the Th&#233;venin resistance can be determined.
Finally, the load is connected to the equivalent circuit. The current through the load is calculated using the current divider formula. Using Ohm&#39;s Law, the Th&#233;venin voltage across the load is determined.
A battery can be represented as the Th&#233;venin equivalent circuit. Th&#233;venin voltage is the battery&#39;s open circuit voltage and resistance is its internal resistance.
Knowing the Th&#233;venin parameters, it is easy to calculate the current for various loads without re-examining the entire circuit.

de stelling van thévenin

Thevinin's Theorem

De stelling van Thévenin speelt een cruciale rol bij de analyse van elektrische circuits en biedt een oplossing voor de uitdagingen die variabele belastingen binnen een circuit met zich meebrengen. In praktische toepassingen is het gebruikelijk om circuits tegen te komen waarin bepaalde elementen vast blijven terwijl andere fluctueren, vaak de "belasting" genoemd. Een typisch huishoudelijk stopcontact is een goed voorbeeld van een variabele belasting, omdat het kan worden aangesloten op een verscheidenheid aan apparaten, elk met zijn eigen unieke elektrische kenmerken. Telkens wanneer een nieuw apparaat wordt aangesloten of verwijderd, vereist het hele circuit een nieuwe analyse. De stelling van Thévenin biedt een techniek die het vaste gedeelte van het circuit vervangt door een equivalent circuit, waardoor analyse en ontwerp worden vereenvoudigd. De stelling van Thévenin stelt dat een lineair circuit met twee aansluitingen kan worden weergegeven door een equivalent circuit dat bestaat uit een voltagesbron in serie met een weerstand. Dit equivalente circuit kapselt effectief het gedrag van het originele circuit in vanuit een extern perspectief. Twee kritische parameters definiëren dit Thévenin-equivalentcircuit: de Thévenin-equivalentvoltage (VTh), die overeenkomt met de nullastvoltage op de klemmen, en de Thévenin-equivalente weerstand (RTh), die de ingangs- of equivalente weerstand op de klemmen vertegenwoordigt wanneer alle onafhankelijke bronnen zijn uitgeschakeld. Om het concept verder te illustreren, bekijken we twee circuits die worden weergegeven in Figure 1 en Figure 2. Deze circuits worden als gelijkwaardig beschouwd als ze op hun aansluitingen dezelfde voltage-stroomrelatie delen. Wanneer de aansluitingen open blijven, waardoor er geen stroom vloeit, zal de voltage over de open aansluitingen de Thévenin-voltage zijn. Wanneer alle onafhankelijke bronnen zijn uitgeschakeld. De weerstand die over de terminals wordt waargenomen, is dan de Thévenin-weerstand. <img alt="Figure1" src="/files/ftp_upload/15053/15053_PT_Figure_1.svg" style="text-align: center; height: 128px;"> Figure 1 <img alt="Equation1" src="/files/ftp_upload/15053/15053_PT_Equation_1.svg" style="text-align: center; height: 14px;"> <img alt="Figure2" src="/files/ftp_upload/15053/15053_PT_Figure_2.svg" style="text-align: center; height: 128px;"> Figure 2 <img alt="Equation2" src="/files/ftp_upload/15053/15053_PT_Equation_2.svg" style="text-align: center; height: 14px;"> Om dit idee praktisch toe te passen en het Thévenin-verzet te bepalen, moeten we twee scenario’s overwegen: GEVAL 1: In situaties waarin het netwerk geen afhankelijke bronnen bevat, worden alle onafhankelijke bronnen gedeactiveerd en wordt de ingangsweerstand vastgesteld, wat de weerstand is die wordt waargenomen tussen de aansluitingen a en b. GEVAL 2: Wanneer het netwerk afhankelijke bronnen bevat, ga dan door met het deactiveren van alle onafhankelijke bronnen. U mag afhankelijke bronnen echter niet deactiveren, aangezien deze worden bestuurd door circuitvariabelen. Het is vermeldenswaard dat de waarde van de Thévenin-weerstand (RTh) soms negatief kan zijn, wat betekent dat het circuit stroom levert in plaats van verbruikt. Dit scenario is haalbaar in circuits met afhankelijke bronnen.

De stelling van Thévenin

Thevenin&#39;s theorem states that any linear two-terminal circuit can be replaced by an equivalent circuit with a single voltage source in series with a ...

Education

JoVE Core

Electrical Engineering

Elektrotechniek

Unit 1

DC Circuit Analysis

DC-kringanalyse

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

thevenin circuit equivalents

Thevenin circuit equivalents simplify linear two-terminal circuits by replacing the fixed part of a network with one equivalent source and one resistor. This method is useful when a circuit has a fixed section and a load that can change. A household electrical outlet is a familiar example, because different appliances can be plugged in or removed. Each change in load can require a new circuit analysis, so an equivalent circuit makes the work easier.

Thevenin's theorem states that a linear two-terminal circuit can be represented by a voltage source in series with a resistor. From the outside, this equivalent circuit has the same behavior as the original network. Two circuits are considered equivalent when they have the same voltage-current relationship at their terminals. The Thevenin equivalent voltage, VTh, is the open-circuit voltage at the terminals, and the Thevenin equivalent resistance, RTh, is the input resistance seen at the terminals when the independent sources are turned off.

To find the Thevenin resistance, the method depends on the kind of sources in the network. If the circuit has no dependent sources, all independent sources are deactivated and the resistance between terminals a and b is found. If the network includes dependent sources, the independent sources are still turned off, but the dependent sources stay active because they are controlled by circuit variables. In some cases, RTh can be negative. That means the circuit is supplying power instead of consuming it, which can happen in circuits with dependent sources.

Thevenin Circuit Equivalents

nodal analysis

Using Node Voltages in Circuit Analysis

Nodal analysis uses node voltages to simplify circuit analysis. In this method, the voltage at each node becomes the main variable. Once those voltages are known, they can be used to find other values, such as the current through specific circuit parts. The process begins by choosing a reference node, also called a datum node. This node is selected for convenience and assigned a voltage of zero. The other nodes, called non-reference nodes, are then measured relative to that point. In the...

nodal analysis with voltage sources

Supernode Equations in Nodal Analysis

Nodal analysis uses node voltages and Kirchhoff’s laws to solve circuits with voltage sources. It is a systematic method for breaking a complex circuit into smaller parts that are easier to analyze. In this example, the circuit includes four resistors and two voltage sources. One voltage source is connected between a non-reference node and the reference node. In that case, the non-reference node voltage can be written directly as the source voltage. This removes one unknown and makes the...

mesh analysis

Mesh Currents for Circuit Analysis

Mesh currents give students a simpler way to analyze planar circuits. In mesh analysis, the unknowns are currents, not voltages. The method uses Kirchhoff's voltage law, or KVL, to build the equations needed to solve the circuit. A mesh is a closed loop in a circuit that does not contain any smaller loops inside it. Each independent mesh is assigned a mesh current, and this current is usually drawn in the clockwise direction. These mesh currents are used as the main circuit variables during...

mesh analysis with current sources

Current Sources in Mesh Circuit Analysis

Current sources make mesh circuit analysis easier because they can reduce the number of equations needed. This applies to both independent and dependent current sources. The method depends on where the current source is placed in the circuit. When a current source appears in only one mesh, the setup is simple. Assign mesh currents as usual, but leave out the mesh that contains the current source from the equation process. Then apply Kirchhoff's voltage law, or KVL, to the remaining mesh to get...

source transformation

Circuit Source Equivalents

Circuit source equivalents make it easier to simplify electrical circuits in circuit analysis. A source transformation replaces a voltage source in series with a resistor by a current source in parallel with a resistor, or it replaces a current source in parallel with a resistor by a voltage source in series with a resistor. The key idea is that the equivalent resistance at the circuit terminals stays the same when the original sources are turned off. When making the change, the current source...

linear circuits

Circuit Linearity and Resistor Behavior

Circuit linearity describes how a circuit responds when its input changes. A linear circuit has an output that is directly proportional to its input. This behavior follows two rules: homogeneity and additivity. Homogeneity means that if the input, or excitation, is multiplied by a constant factor, the response is multiplied by the same factor. For example, if the current is increased by a constant k, the voltage also increases by k times. Additivity means that the response to a sum of inputs...

superposition theorem

Analyzing Circuits with Superposition

Superposition is a circuit analysis method for linear circuits with more than one independent source. It lets you find the voltage across or current through an element by adding the separate effects of each source acting alone. To use superposition, keep one independent source active and turn off the others. A voltage source is replaced by a short circuit, and a current source is replaced by an open circuit. Then calculate the output from the single active source. Repeat the process for each...

thevinin's theorem

Thevenin circuit equivalents simplify linear two-terminal circuits by replacing the fixed part of a network with one equivalent source and one resistor. This method is useful when a circuit has a fixed section and a load that can change. A household electrical outlet is a familiar example, because different appliances can be plugged in or removed. Each change in load can require a new circuit analysis, so an equivalent circuit makes the work easier. Thevenin's theorem states that a linear...

norton's theorem

Norton Equivalent Circuit in DC Analysis

Norton equivalent circuit in DC analysis shows how a linear two-terminal circuit can be replaced by a simpler network. The replacement uses a current source, called I_N, in parallel with a resistor, called R_N. I_N is the short-circuit current through the terminals, and R_N is the input or equivalent resistance seen at the terminals when the independent sources are turned off. To find Norton's resistance, all independent sources in the circuit are set to zero. The resistance measured at the...

maximum power transfer

Load Matching in Thevenin Circuits

Load matching in Thevenin circuits helps a source deliver the most power to a connected load. This matters in engineering fields such as telecommunications, where power delivery must be optimized. Even then, internal losses can be significant and may equal or exceed the power sent to the load. The Thevenin equivalent circuit is a useful way to study this situation. It replaces the full linear circuit with a simpler source and resistance while keeping the load in place. In this setup, the load...

design example: strain gauge bridge or wheatstone bridge

design-example-strain-gauge-bridge-or-wheatstone-bridge

Wheatstone Bridge Output for Strain Gauge Design

A strain gauge and Wheatstone bridge work together to turn mechanical strain into an electrical signal. In engineering, this setup is often used to measure force or pressure. Each part of the bridge has a resistance that changes slightly when strain is applied. The main goal is to turn a very small voltage output into a larger, easier-to-read signal. A voltmeter can then measure that output more clearly. To do this, an engineer designs the strain gauge circuit and figures out how much...

key terms and concepts

Learn how Thevenin’s theorem replaces a linear two-terminal circuit with a voltage source and resistor, and how to find VTh and RTh in circuit analysis.

Thevenin Circuit Equivalents | JoVE K12

JoVE Core Electrical Engineering offers easy-to-understand animated videos that cover fundamental concepts of electric circuits along with circuit analysis techniques. It incorporates first-order and second-order circuits using operational amplifiers and circuit transformation concepts. The inclusion of practical design examples and real-world applications through scientist-in-action videos adds significant educational value, making complex concepts accessible.

electrical engineering

Thevenin Circuit Equivalents

Description

Transcript

Tags