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Physics 208N004 Lecture #26
– 23 March 2011
Chapter 31: 310 Electromagnetic waves
,
32: 4 Refraction
Complete Chapter 30 and Review
Inductor
Inductive Reactance
Capacitor
Therefore, the current
through an inductor lags
the voltage by 90°.
Therefore, in a capacitor,
the current leads the
voltage by 90°.
Capacitive Reactance
Resistor
V
o
=
I
o
[1/(
C
)
Voltage and current
are in phase
Analyzing the
LRC
series AC circuit is complicated, as the
voltages are not in phase – this means we cannot simply add
them. Furthermore, the reactances depend on the frequency.
308
LRC
Series AC Circuit
We calculate the voltage (and current) using what are called
phasors – these are vectors representing the individual voltages.
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Here, at
t
= 0, the current
and voltage are both at a
maximum. As time goes
on, the phasors will
rotate counterclockwise.
308
LRC
Series AC Circuit
Some time
t
later, the
phasors have rotated.
The voltages across each
device are given by the
x
‐
component of each, and the
current by its
x
‐
component.
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 Spring '09
 GEORGE
 Magnetic Field, electromagnetic waves, series AC circuit, lrc series ac

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