Circuit Analysis Techniques
Equivalent Resistance, Voltage & Current Dividers
EGR 220, Chapter 2
February 4, 2016
•  Review
o Bring questions to office hours
•  Equivalent resistance, Req
o Series and parallel resistors
•  Current divider and voltage divider
•  Mesh and nodal analysis
o Building on KVL and KCL
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Voltage Divider Rule
Voltage Divider: Series R
•  Resistors and elements in Series…
•  Current or voltage is the same for R1 & R2?
•  Current or voltage is partitioned across the
elements?
•  Find v1, v2 in terms of vsrc → derive the
expression
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Voltage Divider: Series R
V-­‐‑Divider Discussion
•  Solve for v1 and v2
o Which resistor will have
the larger V drop?
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Current Divider Rule
Current Divider: Parallel R
•  Resistors, elements and branches in Parallel…
•  Current Divider:
o  I is partitioned, flowing through these resistors
o  What is the relationship of V for each element?
•  Find i1, i2 in terms of isrc
•  Derive the expression…
i
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R1
R2
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Current Divider: Parallel R
I-­‐‑Divider Discussion
•  Solve for i1 and i2
o Which R will carry the larger current?
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Ammeter – Introduced Error
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Ammeter – Introduced Error
•  Find the current i in circuit (a).
•  An ammeter with an internal resistance of 1Ω is
inserted in the network to measure i' as shown
circuit (b). What is i’?
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Voltmeter – Introduced Error
Voltmeter – Introduced Error
•  Obtain the voltage Vo in
circuit (a).
•  Determine the voltage V’o
measured when a voltmeter
with 6-kΩ internal resistance
is connected as in figure (b)
o  Calculate the percent error as
Vo −V 'o
×100%
Vo
•  Find the percent error if the
internal resistance were
36kΩ.
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Fundamental Analysis Tools for the Semester
•  Basic analysis laws
o Ohm’s law
o KVL: Kirchhoff’s voltage law
o KCL: Kirchhoff’s current law
•  Analysis tools using the basic laws
o Equivalent resistance
o Current divider
o Voltage divider
o Mesh analysis
o Nodal analysis
o Equivalent Circuits
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