Download (p.946) Ch 33 Alternating Current Circuits 33.3

Fig 33-CO, p.1033
Ch 33 Alternating Current Circuits
33.1 AC Sources and Phasors
v = Vmaxsint
 = 2/T = 2f
Vmax
v = Vmaxsint
t
Phasor
CT1: The phasor diagrams below represent three oscillating
voltages having different amplitudes and frequencies at a
certain instant of time t = 0. As t increases, each phasor
rotates counterclockwise and completely determines a
sinusoidal oscillation. At the instant of time shown, the
instantaneous value of v associated with each phasor is given
in ascending order by diagrams
A. a,b,c.
B. a,c,b.
C. b,c,a.
D. b,a,c.
E. c,a,b
F. c,b,a
CT2: Consider the pairs of phasors below, each shown at t =
0. All are characterized by a common frequency of oscillation
. If we add the oscillations, the maximum amplitude is
achieved for pair(s)
A. a.
B. b.
C. c.
D. d.
E. e.
F. c and d.
G. a and c.
H. b and c.
Ch 33 Alternating Current Circuits
33.2 Resistors in an AC Circuit
iR = vR/R = Vmaxsint/R = Imaxsint
Imax = Vmax/R
Ch 33 Alternating Current Circuits
33.2 Resistors in an AC Circuit
Irms = Imax/21/2 Vrms = Vmax/21/2
Pav = Prms = Irms2R = Vrms2/R
Vrms = IrmsR
P33.2 (p.946)
P33.4 (p.946)
Ch 33 Alternating Current Circuits
33.3 Inductors in an AC Circuit
vL = Vmaxsint
Imax = Vmax/L
iL = Imaxsin(t - /2)
lags voltage by /2
P33.11 (p.946)
Imax = Vmax/XL
XL = L
Ch 33 Alternating Current Circuits
33.4 Capacitors in an AC Circuit
vL = Vmaxsint
Imax = CVmax
iC = Imaxsin(t + /2)
leads voltage by /2
P33.15 (p.946)
XC = 1/C
Imax = Vmax/XC
CT3: The light bulb has a resistance R, and the
emf drives the circuit with a frequency .
The light bulb glows most brightly at
A. very low frequencies.
B. very high frequencies.
C. the frequency  = (1/LC)1/2
Fig 33-14, p.1044
Ch 33 Alternating Current Circuits
33.5 RLC Series Circuit
v = Vmaxsint
Imax = Vmax/Z
i = Imaxsin(t - )
I lags voltage by 
Z = (R2 + (XL – XC)2)1/2
 = tan-1[(XL –XC)/R]
i
P33.17 (p.946)
P33.27 (p.947)
Ch 33 Alternating Current Circuits
33.6 Power in an AC Circuit
Pav = Prms = IrmsVrmscos
cos is called the power factor
Check P33.27 (p.947)
i
Ch 33 Alternating Current Circuits
33.7 Resonance in a Series RLC Circuit
Pav = Vrms2R/(R2 + L2(2 - 02)2/2)
0 = (1/LC)1/2
Q = 0/
i
 = R/L
CT4: For the RLC series circuit shown, which of
these statements is/are true:
(i) Potential energy oscillates between C and L.
(ii) The source does no net work: Energy lost
in R is compensated by energy stored in C and L.
(iii) The current through C is 90° out of phase
with the current through L.
(iv) The current through C is 180° out of phase
with the current through L.
(v) All energy is dissipated in R.
A. all of them
B. none of them
C. (v)
D. (ii)
E. (i), (iv), and (v)
F. (i) and (v)
G. none of the above
P33.38 (p.948)
Ch 33 Alternating Current Circuits
33.8 The Transformer and Power Transmission
V2 = N2V1/N1
Ideal Transformer: Ppri = I1V1 = Psec = I2V2
P33.41 (p.948)
V2
i
CT5: When the switch is closed, the potential
difference across R is
A. V(N2 /N1).
B. V(N1/N2).
C. V.
D. zero.
E. insufficient information
CT6: The primary coil of a transformer is
connected to a battery, a resistor, and a switch.
The secondary coil is connected to an ammeter.
When the switch is thrown closed, the ammeter
shows
A. zero current.
B. a nonzero current for a short instant.
C. a steady current.