Physics with Trig II

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Physics with Trig II
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Where weve been

• Mechanics
• Solids Fluids
• Thermal Physics
• Sound
• The Electric Field
• Electric Potential Capacitance
• Current Resistance
• Direct Current Circuits
• Magnetism
• Induced Voltage

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Where were going

• Ch 21 Alternating Current Circuits and em Waves
• Resistors, capacitors, and inductors in ac
  circuit
• The RLC circuit
• Resonance in ac circuit
• The Transformer

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(21.1) Resistors in an AC Circuit
For PURE resistance, current in phase with
voltage
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(21.1) Resistors in an AC Circuit, contd
Define RMS root, mean, square Peak Vmax or
Imax Average what is average of a sine wave?
See notation Table 21.1, page 655
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(21.1) Resistors in an AC Circuit, contd
Ohms Law from DC circuits
Problem 21-2
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(21.2) Capacitors in ac Circuit
Notice DC
What happens when the switch closes? I leads V
by 90 o in purely capacitive circuit.
Capacitive Reactance
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(21.3) Inductors in ac Circuits
Notice DC
What happens when the switch closes? V leads I
by 90 o in purely inductive circuit.
Inductive Reactance
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(21.3) Capacitors in ac Circuits, contd
E
L
I
I
C
E
ELI the ICE man
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(21.4) The RLC Circuit
? V max across R, C, and L do not occur at the
same time. Z ? Impedance total opposition to
current flow

• Demo of RLC circuit phase shift

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(21.4) The RLC Circuit, contd
Problem 21-20
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(21.5) Power in ac Circuit
No power loss (energy used) in pure inductance or
pure capacitance. Only R uses power.
More
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(21.5) Power in ac Circuit, contd
More
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(21.5) Power in ac Circuit, contd
Power used only by Resistance
More
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(21.5) Power in ac Circuit, contd
But, Always
Problem 21-29
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(21.6) Resonance
When XL XC Applications Tuning a radio
reciever Metal detector Traffic-Light Sensor
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(21.7) Transformer
Also, approximately
Automobile high-voltage ignition coil
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(21.10) em Waves Produced by Antenna

• em wave is a transverse wave
• em consists of E B Page 669

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(21.12) Spectrum of em Waves
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The End