Chapter 26 Reading Quiz AC Circuits - Home - Physics & …physics.gsu.edu/dhamala/Phys1112/Slides/Chapter26.pdf · · 2010-03-18• Capacitor circuits Chapter 26 AC Circuits

• AC sources

• Resistor circuits and AC power

• The transmission and use of electricity

• Capacitor circuits

Chapter 26

AC Circuits

Topics:

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley.

• Capacitor circuits

• Inductors and inductor circuits

• Oscillation circuits

Sample question:Transmission lines carry alternating current at voltages as high as 500,000 V. Why are such high voltages used? And why can birds

perch safely on such high-voltage wires?

Transmission lines carry alternating current at voltages as high as 500,000 V. Why are such high voltages used? And why can birds

voltage wires?

Slide 26-1

Reading Quiz

1. What is the name of the device that is used to change the voltage of AC electricity?

A. Reactor

B. Circuit breaker

C. Inductor

D. Transformer


What is the name of the device that is used to change the

Slide 26-2

1. What is the name of the device that is used to change the

voltage of AC electricity?

D. Transformer

Answer


What is the name of the device that is used to change the

Slide 26-3

Reading Quiz

2. What quantity with units of ohms, besides resistance, is

introduced in this chapter?

A. Inductance

B. Reactance

C. GFI

D. Transformance


What quantity with units of ohms, besides resistance, is

Slide 26-4

2. What quantity with units of ohms, besides resistance, is introduced in this chapter?

B. Reactance

Answer


What quantity with units of ohms, besides resistance, is

Slide 26-5

An AC Voltage Source


The circuit symbol for an AC voltage source

Slide 26-6

Resistor Circuits

Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Slide 26-7

Resistor Voltages and Currents


vR = VR co

iR =vR

R=

VR cos 2

R

Lowercase symbols represent

instantaneous values of current or

voltage. They change sinusoidally with

time.

Resistor Voltages and Currents

Uppercase symbols represent

peak values of current or

voltage. They are fixed

quantities.

os 2π f t

2π f t= IR cos 2π f t

Slide 26-8

AC Power in Resistors


PR =1

2IR

2R

Average power loss in a

resistor with peak current IR

2

Slide 26-9

If we define

Root-Mean-Square Current and Voltage

Irms =IR

2and

then we can write

PR =IR

2

R = (


PR =2

R = (

and

PR = I rms( )2

R =Vrm(

R

The expressions for AC power are identical to those used for DC

currents if rms currents and voltages are used.

Square Current and Voltage

Vrms =VR

2

Irms( )2

RIrms( ) R

ms )2

R= IrmsVrms

The expressions for AC power are identical to those used for DC

currents if rms currents and voltages are used.

Slide 26-10

Transformers


Transformer voltages for primary and

secondary coils with

V2 =N2

N1

V1 or

Transformer voltages for primary and

secondary coils with N1 and N2 turns

(V2 )rms =N2

N1

(V1)rms

Slide 26-11

Checking Understanding

Suppose that an ideal transformer has 10 turns in its primary coil

and 20 turns in its secondary coil. The current through the primary coil is shown in the graph on the upper left. Which of the other graphs best represents the current through the secondary coil?


Suppose that an ideal transformer has 10 turns in its primary coil

and 20 turns in its secondary coil. The current through the primary coil is shown in the graph on the upper left. Which of the other graphs best represents the current through the secondary coil?

Slide 26-12

Answer

Suppose that an ideal transformer has 10 turns in its primary coil and 20 turns in its secondary coil. The current through the primary coil is shown in the graph on the upper left. Which of the other graphs best represents the current through the secondary coil?


Suppose that an ideal transformer has 10 turns in its primary coil and 20 turns in its secondary coil. The current through the primary coil is shown in the graph on the upper left. Which of the other graphs best represents the current through the secondary coil?

Slide 26-13

Transmission of Electrical Power


Transmission of Electrical Power

Slide 26-14

Two-Phase Power

to Your Home


Wiring Inside the Home


Physiological Effects and Electrical Safety


Physiological Effects and Electrical Safety

Slide 26-17

Electrical Dangers


Capacitor Circuits


vC = VC cos 2π f t

Slide 26-19

Voltage, Charge, and

Current for a Capacitor in

an AC Circuit

IC = (2π f C)VC =VC

XCXC

XC =1

2π f C

where


Capacitive Reactance

X =1


XC =1

2π f C

Slide 26-21

Inductance and Inductors

vL = L∆iL

∆t

1 henry = 1

Units of inductance:


The circuit symbol for an inductor

1 henry = 1

1 H = 1 V ⋅ s/A = 1 Ω ⋅ s

Slide 26-22

Inductor Circuits


Inductor Currents and Voltages


Inductor Currents and Voltages

Slide 26-24

Inductive Reactance


VL = (2π f L)IL

IL =VL

2π f L=

VL

XL

or

2π f L XL

XL = 2π f L

where

Slide 26-25

LC Circuits


Energy of an LC Circuit and a Block on a Spring


Circuit and a Block on a Spring

f =1

2π

k

m

Block on spring:

f =1

2π

1

LC

LC circuit:

Slide 26-27

The RLC Circuit


The Driven RLC Circuit

f0 =1

2π

1

LC

Imax =

Ε0

R


The Driven RLC Circuit for Different Values of

I =Ε0

R2

+ XL − XC( )2

=

R


Circuit for Different Values of R

Ε0

R2

+ 2π f L − 1 / 2π f C( )2

Slide 26-30

Documents

Chapter 26 Reading Quiz AC Circuits - Home - Physics & …physics.gsu.edu/dhamala/Phys1112/Slides/Chapter26.pdf · · 2010-03-18• Capacitor circuits Chapter 26 AC Circuits