Dr. Bullock
FORM -A
Physical Principles II –Exam 3
NAME:
Each question is worth 5 points distribute each point on one line of the scantron.
Question 1-5
In a pure resistive circuit, the phase angle between current and voltage is
A. 0
B. π/2 radians
C. -π/2 radians
D. π radians
E. 3π/4 radians
Question 6-10
An electric circuit consists of a resistor connected across the terminals of an ac generator.
How does the power dissipated in the resistor change as the frequency in the generator
decreases?
A. It decreases
B. It increases
C. It does not change
D. It increases or decreases depending on the sign of the phase angle
E. Need more information
Question 11-15
If you triple the rms voltage in an ac circuit, what happens to the maximum voltage?
A. It increases by a factor of 3
B. It decreases by a factor of 3
C. It decreases by a factor of 3
D. It increases by a factor of 3
E. It increases by a factor of 9
Question 16-20
An LC circuit consists of a 1-µF capacitor and a 4mH inductor. Its oscillation frequency
is approximately:
A. 0.025 Hz
B. 25 Hz
C. 60 Hz
D. 2500 Hz
E. 15, 800 Hz
Dr. Bullock
FORM -A
Physical Principles II –Exam 3
Question 21-25
The above figure shows a simple ac circuit consisting of an inductor connected across the
terminals of an ac generator. If the frequency of the ac generator is decreased by a factor
of four, what will happen to the inductive reactance on the inductor?
A. It decreases by a factor of eight
B. It decreases by a factor of four
C. It increases by a factor of two
D. It increases by a factor of four
E. It increases by a factor of eight
Question 26-30
What is the phase angle between the voltages of the inductor and capacitor in a RLC
series circuit?
A. zero
B. 45°
C. 90°
D. 180°
E. 270°
Question 31-35
Resonance in a series RLC circuit occurs when
A. XL is greater than XC
B. XC is greater than XL
C. (XL - XC) is equal to R2
D. (XL - XC)2 is equal to R2
E. XC equals XL
Dr. Bullock
FORM -A
Physical Principles II –Exam 3
Question 36-40
A series RLC circuit has a 100-Ω resistor, 2.00-mH inductor and a 4.00-μF capacitor
connected across a 120-V rms ac source at (1000/π) Hz. What is the power dissipated by
the circuit?
A. 184 W
B. 18.6 W
C. 58.4 W
D. 91.8 W
E. 180 W
Question 41-45
Consider: radio waves (r), visible light (v), infrared light (i), x-rays (x), and ultraviolet
light (u). In order of increasing frequency, they are:
A. r, v, i, x, u
B. r, i, v, u, x
C. i, r, v, u, x
D. i, v, r, u, x
E. r, i, v, x, u
Question 46-50
Which of the following is NOT true for electromagnetic waves?
A. they consist of changing electric and magnetic fields
B. they travel at different speeds in vacuum, depending on their frequency
C. they transport energy
D. they transport momentum
E. they can be reflected
Question 51-55
In an electromagnetic wave the E and B fields are oriented such that
A. they are parallel to one another and perpendicular to the direction of wave
propagation
B. they are parallel to one another and parallel to the direction of wave
propagation
C. they are perpendicular to one another and perpendicular to the direction of
wave propagation
D. they are perpendicular to one another and parallel to the direction of wave
propagation
E. None of the above answers is correct
Dr. Bullock
FORM -A
Physical Principles II –Exam 3
Question 56-60
For an xyz coordinate system shown in Figure 25-2, if the E-vector is in the +z direction,
and the B-vector is in the +x direction, what is the direction of propagation of the
electromagnetic waves?
A. +y
B. -y
C. +x
D. -x
E. +z
Question 61-65
Which one of the following is not an electromagnetic wave?
A. UV
B. infrared
C. radio waves
D. sound waves
E. gamma rays
Question 66-70
A Doppler weather radar operates at a frequency of 3.40 GHz. The wave from this radar
system reflects from an approaching weather system moving with a speed of 39.0 m/s.
What is the difference in frequency between the outgoing and returning waves?
A. 442 Hz
B. 351 Hz
C. 419 Hz
D. 322 Hz
E. 670 Hz
Dr. Bullock
FORM -A
Physical Principles II –Exam 3
Question 71-75
The magnetic field component of the electromagnetic wave is 15.0 μT. What is the
magnetic energy density of the wave?
A. 2.26 × 10-4 J/m3
B. 8.95 × 10-5 J/m2
C. 1.79 × 10-4 J/m3
D. 4.47 × 10-4 J/m2
E. 9.72 × 10-5 J/m3
Dr. Bullock
FORM -A
SHOW ALL YOUR WORK!
Physical Principles II –Exam 3
NAME
(10 POINTS)
The above figure shows the phasor diagram for an RLC circuit in which the impedance is
337 . (a) What is the resistance, R, in this circuit? (b) Is this circuit driven at a
frequency that is greater than, less than, or equal to the resonance frequency of the
circuit? Explain.
Dr. Bullock
FORM -A
SHOW ALL YOUR WORK!
Physical Principles II –Exam 3
NAME
(10 POINTS)
A beam of vertically polarized light encounters two polarizing filters, as shown in the
above figure. (a) Rank the three cases, A, B, and C, in order of increasing transmitted
intensity. Indicate ties where appropriate. (b) Calculate the transmitted intensity for each
of the cases in the figure, assuming that the incident intensity is 37.0 W/m2. Verify that
your numerical results agree with the rankings in part (a).Continue your work on the next
page if necessary.
Dr. Bullock
FORM -A
Physical Principles II –Exam 3
Physical Principles II –Exam 3
Dr. Bullock
FORM -A
Walker, Physics, 3rd Edition
Chapter 24
Numbered Equations
V  Vmax sin t
24-1
I rms  ( I 2 )av 
1
2
Imax
24–3
RMS Value of a Quantity with Sinusoidal Time Dependence
( x 2 ) av 
x max 2
1
2
x rms 
1
2
x max
24–4
Vrms 
1
2
Vmax
24–5
Irms  CVrms
24–7
I rms 
Vrms
XC
24–8
Capacitive Reactance, X C
XC 
1
24–9
C
SI unit: ohm, 
Vmax  Vmax, R 2  Vmax,C 2
24–10
Impedance in an RC Circuit
2
Z R X
2
C
 1 
 R 

 C 
2
2
24–11
Physical Principles II –Exam 3
Dr. Bullock
FORM -A
SI unit: ohm, 
I max R R

I max Z Z
24–12
Pav  I rmsVrms cos 
24–13
cos  
Inductive Reactance, X L
X L  L
24–14
SI unit: ohm, 
Impedance in an RL Circuit
Z  R2  X L 2  R2  (L) 2
24–15
SI unit: ohm, 
Impedance of an RLC Circuit
1 

Z  R 2  ( X L  X C ) 2  R 2   L 

C 

2
24–16
SI unit: ohm, 
tan  
I max ( X L  XC ) X L  XC

I max R
R
24–17
Natural Frequency of an LC Circuit
0 
1
 2f
LC
SI unit: s 1
24–18
Physical Principles II –Exam 3
Dr. Bullock
FORM -A
Walker, Physics, 3rd Edition
Chapter 25
Numbered Equations
Speed of Light in a Vacuum
c  300
.  108 m s
c
25–1
1
25–2
 0 0
 u
f '  f 1  
c

25–3
c f
25–4
u  uE  u B  12  0 E 2 
u  12  0 E 2 
1
E rms 
E max
Brms 
Bmax
B2   0 E 2 
2 0
2
uav  12  0 Erms

1
B2
2 0
1
2 0
25–5
1
0
B2
2
2
Brms
  0 Erms

25–6
1
0
2
Brms
25–7
2
25–8
2
E  cB
I  uc  12 c 0 E 2 
25–9
1
c 2
cB2  c 0 E 2 
B
2 0
0
25–10
Dr. Bullock
FORM -A
p
U
c
pressure av 
Physical Principles II –Exam 3
25–11
I av
c
25–12
Law of Malus
I  I 0 cos2 
25–13
Transmitted Intensity for an Unpolarized Beam
I  21 I 0
25–14