Transcript PHY2054-PPT22

Chapter 22
Alternating Current
PowerPoint Lectures for
College Physics, Eighth Edition
Hugh D. Young and Robert M. Geller
Lectures by James L. Pazun
Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley
Goals for Chapter 22
• To study phasors and alternating current.
• To explore and calculate resistance and reactance.
• To diagram and solve examples of the series R-L-C
circuit.
• To calculate and graph power in alternating –
current circuits.
• To study series and parallel resonance.
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Alternating current - Figure 22.1
• A coil of wire rotating
with constant angular
velocity in a magnetic
field develops a
sinusoidal oscillating
current.
• The potential will vary
from a maximum V at a
frequency ω (or, by a
factor of 2π, as f in Hz).
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What are phasors? – Figure 22.2
• Phasors are graphic
representations of location.
In two dimensions, you can
locate a unique point with
a radius vector of length L
and its angle with respect
to zero.
•This figure refers to
conceptual analysis 22.1.
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Root-Mean-Square averages – Figure 22.4
• Refer to example 22.4 in
your text.
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Resistance and Reactance – Figure 22.6
• For a circuit
such as one
shown at the
right, there is a
resistor and one
can calculate the
potential and
current. BUT in
an AC circuit,
these are
functions of
time.
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An Inductor in a circuit – Figure 22.7
Refer to Example 22.2 in your text. The circuit leads to the
RMS graph which leads to the phasor diagram.
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A capacitor in an AC circuit – Figure 22.8
• Even though we don’t
think of capacitors as
transparent to current, we
can have one plate charge
then immediately have the
opposing plate charge.
We think of AC as going
past or through a
capacitor.
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Capacitors and AC circuits II – Figures 22.9,10
• Refer to the worked examples in Conceptual Analysis 22.2
and also in Example 22.3.
For use with
the conceptual
analysis.
For use with the
worked example
on page 743.
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The series R-L-C circuit – Figure 22.12
• Consumer
electronics
would be a
good place
to find such
a circuit.
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Current and voltage may be found – Figure 22.13
As in Figure 22.8, here too we can follow the logic from circuit to
phasor diagrams.
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R-L-C Circuits – Figure 22.14
• Refer to worked Example 22.4 and Conceptual Analysis
22.3.
• You will want to take advantage of the Problem Solving
Strategy 22.1
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Power in Alternating Current Circuits – Figure 22.15
• AC current behaves differently with respect to power than DC
current. It was the crucial difference that made long-distance
wiring possible.
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Power in AC Circuits II – Figures 22.16,17
• Follow from phasor diagram to Conceptual Analysis 22.4 to
worked Examples 22.5 and 22.6.
“Generic” diagram
Specific to the Conceptual
Analysis
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Series Resonance – Figure 22.18
• Since the AC
flow is
expressed in
terms of
frequency, it
follows that just
like in music,
these
frequencies can
resonate.
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Series resonance II – Figures 22.19, 20
A “generic” diagram
illustrating waveforms in
resonance.
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• Refer to Conceptual
Analysis 22.5 and worked
Example 22.7.
Parallel resonance – Figure 22.21
Refer to worked Example
21.8 in your text.
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