Download Chapter 22: Alternating Current

Chapter 22 Lecture
Chapter 22:
Alternating
Current
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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 alternatingcurrent 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 22.1 in your text.
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Resistance and Reactance – Figure 22.6
• For a circuit such as
the 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 – Figures 22.9
and 22.10
• Refer to the worked examples in Conceptual Analysis 22.2 and also
in Example 22.3.
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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, we can follow the logic from
circuit to phasor diagrams here, too.
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R-L-C Circuits – Figure 22.14
• Refer to Example 22.4 and Conceptual Analysis
22.3.
• You will want to take advantage of 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 does DC current. It was the crucial
difference that made long-distance wiring
possible.
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Power in AC Circuits – Figures 22.16 and
22.17
• Follow from phasor diagram to Conceptual
Analysis 22.4 to Examples 22.5 and 22.6.
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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 – Figures 22.19 and 22.20
• A generic diagram
illustrating waveforms
in resonance.
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• Refers to Conceptual
Analysis 22.5 and
Example 22.7.