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Tufts University
School of Engineering
Department of Electrical and Computer Engineering
ES3  Introduction to Electrical Circuits
Fall 2007
Lab Section: Tuesday 2:30 – 4:30
(I did a make up lab on Friday, October 26 instead of my normal Tuesday section)
Experiment 3
Thevenin Equivalent Circuits and Maximum Power Transfer
Name:
xxxxx
xxxx@ tufts.edu
Submitted to:
xxx
Experiment Performed:
xxx
Experiment Due:
11xxxx
Worked with:
xxxxxx
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View Full Document Purpose
The purpose of this lab was to determine the Thevenin equivalent of various
electrical components.
In addition, the Maximum Power Transfer theorem was used.
By
using these two concepts along with various lab devices and a bread board, the goal was
to become more familiar with many very common uses and applications of electrical
engineering.
Introduction
The main component of this lab that was used to connect the circuits was a device
called a breadboard.
It is used to quickly test various circuits because it contains all of
the wiring internally, and the element can be simply placed in the holes that correspond to
the desired circuit.
The design of the breadboard allows for this simplicity.
In the front,
there are tie points that are mainly used for distributing power supply voltages throughout
the entire board.
The rest of the board can be used to connect circuit elements in various
ways.
Circuit elements that are all connected in one row are in series. When the left lead
of each element is connected to one column and the right lead of each to another column,
the elements are said to be in parallel.
The breadboard was the base from which the rest
of the lab was built.
Using this tool, Thevenin equivalent circuits (TEC) of various electrical elements
were studied.
A Thevenin equivalent consists of an independent voltage source in series
with a resistance.
This circuit is open at the end meaning that no current runs through it.
Because of this, the Thevenin voltage will be equal to the open circuit voltage.
In order
to find the Thevenin resistance, the open circuit can be shorted, allowing a current to run
through it.
Using Ohm’s Law, the resistance is then calculated by dividing the Thevenin
voltage by the current through the short circuit.
In a similar circuit where a resistor is
placed across the open terminals of the equivalent circuit, it is still possible to solve for
the Thevenin resistance.
In order to do this, the voltage across the additional resistor
needs to be measured.
Then, using Kirchhoff’s voltage law, the voltage across the
Thevenin resistor can be found.
Dividing this by the current (found using Ohm’s Law)
will yield the Thevenin resistance.
The next important part of the lab was the use of the Maximum Power Transfer
theorem.
This theorem states that the load resistance (resistance placed across the open
terminals in the Thevenin equivalent) that absorbs the maximum power from a two
terminal circuit is equal to the Thevenin resistance.
Thus, various derivations and
equations yield a final equation expressing the maximum absorbed power in the load
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This note was uploaded on 03/31/2008 for the course ENGINEERIN ES3 taught by Professor Zatet during the Fall '07 term at Tufts.
 Fall '07
 Zatet
 Electrical Engineering

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