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LECTURE 24
Pick up • lecture notes
Pick up • lecture notes
Average and root-mean-square
T
av tdtIT
I0
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av tdtIT
I0
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2
2/1
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2 )(1
avrms
T
rms
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tdtIT
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avrms
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rms
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Exercise 1: The average of the voltage signal shown is(a) Vo(b) 0(c) Vo/2
The rms of the voltage signal shown isa.) Vo b.) 0 c.) Vo/2 d.)
Exercise 1: The average of the voltage signal shown is(a) Vo(b) 0(c) Vo/2
The rms of the voltage signal shown isa.) Vo b.) 0 c.) Vo/2 d.) 2/0V
Exercise 2: The voltage signal is rectified” by eliminating negative voltages. The rms for the rectified signal is (a) 0(b) Vo(c) Vo/2(d)
The average for the rectified signal is a) 0 b.) Vo c.) Vo/2 d.)
Exercise 2: The voltage signal is rectified” by eliminating negative voltages. The rms for the rectified signal is (a) 0(b) Vo(c) Vo/2(d)
The average for the rectified signal is a) 0 b.) Vo c.) Vo/2 d.)
20V
Rectified
20V
Resistor in AC circuit
RtItE )()( RtItE )()(
Kirchhoff’s law
RtItE
tEtE
)()sin(
)sin()(
0
0
)sin()( 0 tR
EtI
Current in phase with voltageCurrent in phase with voltage
Concept Test: As the frequency of the generator is increased, the average power dissipated in the resistor A) increases. B) does not change. C) may increase or decrease depending on the magnitude of the original frequency.
Concept Test: As the frequency of the generator is increased, the average power dissipated in the resistor A) increases. B) does not change. C) may increase or decrease depending on the magnitude of the original frequency.
Inductor in AC circuit
)sin()cos()(
)()()(
)cos()(
00
0
tL
Et
L
EtI
dt
tdILtVtE
tEtE
L
)2/cos()( 0 tItI
Voltage leads the current by 90 degreesVoltage leads the current by 90 degrees
LX L XL: inductivereactance
Effectiveresistance
Concept Test: As the frequency of the generator is doubled, the maximum current through the inductor
A) increases by a factor of 2. B) does not change. C) decreases by a factor of 2. D) increases by a factor of 4. E) decreases by a factor of 4.
Concept Test: As the frequency of the generator is doubled, the maximum current through the inductor
A) increases by a factor of 2. B) does not change. C) decreases by a factor of 2. D) increases by a factor of 4. E) decreases by a factor of 4.
Capacitor in ac circuits
)sin()(
)(
)()()(
)cos()( 0
tCdt
tdQtI
C
tQtVtE
tEtE
C
)2/cos()/(1
)( 0
tC
EtI )2/cos(
)/(1)( 0
t
C
EtI
CXC
1 Capacitative reactance
Voltage lags the current by 90 degreesVoltage lags the current by 90 degrees
Concept Test: The loudspeaker shown belowreceives from the amplifier both high and lowfrequency signals. Which speaker emits the high frequency signals:
A) speaker 1B) speaker 2C) both speakersD) need more information.
Concept Test: The loudspeaker shown belowreceives from the amplifier both high and lowfrequency signals. Which speaker emits the high frequency signals:
A) speaker 1B) speaker 2C) both speakersD) need more information.
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