Table of Contents
Exam 1
Exam 2
Exam 3
Exam 4
Final Exam
Lecture 17
Lecture 18
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Syllabus
Lecture 19
Lecture 20
Lecture 21
Lecture 22
Lecture 23
Lecture 24
Study guide 3
Formula sheet 3
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User Instructor: Rizal F. Hariadi
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Study guide Exam 3
Calendar Last compiled on March 27, 2024
Envelope-open rhariadi@asu.edu
CHROME www.rizalhariadi.com
Twitter @result_hariadi
iClicker
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Two long parallel wires are placed side-by-side on a horizontal table.
If the wires carry current in opposite directions,
A. One wire is lifted slightly while the other is forced downward
against the table’s surface. Both wires are raised slightly.
B. the wires pull toward each other.
C. the wires push away from each other.
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A. into the page
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A negatively charged particle –Q is moving to the right, directly
above a wire having a current I flowing to the right, as shown in the
figure. In what direction is the magnetic force exerted on the particle
due to the current?
B. out of the page
C. downward
D. upward
E. The magnetic force is zero because the velocity is parallel to
the current.
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A. 1.2 A
B. 2.5 A
C. 4.9 A
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A thin copper rod 1.0 m long has a mass of 0.050 kg and is in a
magnetic field of 0.10 T. What minimum current in the rod is needed
for the magnetic force to balance the weight of the rod?
D. 9.8 A
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A. True
B. False
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According to Faraday’s law, a coil in a strong magnetic field must
have a greater induced emf E in it than a coil in a weak magnetic
field.
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A bar magnet is close to a solenoid, as shown in the figure. As
viewed through the solenoid looking toward the magnet, what is the
direction (clockwise or counterclockwisE. of the current (if any)
induced in the solenoid in each case?
A. The magnet is pushed toward the solenoid.
B. The magnet and solenoid both move to the right at 25 cm/s.
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A. 0 T · m2
B. 3.1⇥10
C. 5.1⇥10
3 T · m2
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A flat circular loop of radius 0.10 m is rotating in a uniform magnetic
field of 0.20 T. Find the magnetic flux through the loop when the
plane of the loop and the magnetic field vector are parallel.
3 T · m2
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A flat circular loop having one turn and a radius of 5.0 cm is
positioned with its plane perpendicular to a uniform 0.60-T magnetic
field. The area of the loop is suddenly reduced to essentially zero in
0.50 ms. What is emf E induced in the loop?
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A. 4 "o
B. 2 "o
C. "o
D. "o /2
E. "o /4
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An AC generator consisting of a coil with N turns rotating at angular
speed ! in an external magnetic field B produces a maximum emf E
"o .If you now decrease the number of turns in the coil to N /2 and at
the same time cause it to rotate twice as fast, what will be the new
maximum emf E if you do not change any of the other quantities?
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A. step-up transformer.
B. step-down transformer.
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If the secondary coil of a transformer contains more loops than the
primary coil, then it is a
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A. True
B. False
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Inductors store energy by accumulating excess charge within their
coils.
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A. 50 W.
B. 100 W.
C. 200 W.
D. none of the given answers.
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The primary of an ideal transformer has 100 turns, and its
secondary has 200 turns. Neglecting frictional losses, if the power
input to the primary is 100 W, we can expect the power output of the
secondary to be
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A. 6.0 V
B. 12 V
C. 0.0 V
D. 4.0 V
E. 8.0 V
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A coil with a self-inductance of 6.0 H has a constant current of 2.0 A
flowing through it for 2.0 s. What is the emf E induced in this coil?
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A. 190 J/cm3
B. 88 J/cm3
C. 240 J/cm3
D. 30, 000 J/cm3
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A large electromagnet has a 22 T magnetic field between its poles.
What is the magnetic energy density in that region of space?
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Magnetism
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strip 1
strip 2
P
S
I1
I2
Q
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On a computer chip, two conducting strips carry charge from P to Q
and from R to S. If the current direction is reversed in both wires, the
net magnetic force of strip 1 on strip 2.
R
A. remains the same.
B. reverses.
C. changes in magnitude but not in direction.
D. changes to some other direction.
E. other
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A. True
B. False
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According to Lenz’s law, the induced current in a circuit always flows
to oppose the external magnetic flux through the circuit.
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A. ultraviolet
B. infrared
C. radio waves
D. sound waves
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Which one of the following is not an electromagnetic wave?
E. gamma rays
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Wave characteristics
A. ultraviolet
B. infrared
C. radio waves
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Which one of the following types of electromagnetic waves travels
through a vacuum the fastest?
D. gamma rays
E. They all travel through space at the same speed.
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Wave characteristics
A. 22.6 m
B. 226 m
C. 326 m
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What is the wavelength used by a radio station that broadcasts at a
frequency of 920 kHz?
D. 175 m
E. 276 m
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One light year
A. 1.58 ⇥ 1014 m.
B. 9.46 ⇥ 1015 m.
C. 3.94 ⇥ 1014 m.
D. 2.59 ⇥ 1013 m.
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How far does light travel in a year (a light year)?
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Wave number
A. 1 ⇥ 108 m.
B. 1 ⇥ 108 /m.
C. 1 ⇥ 107 m.
D. 1 ⇥ 107 /m.
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What is the angular wave number k for f = 5 ⇥ 1014 Hz?
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EM Waves
A. 3.07 cm
B. 2.07 cm
C. 1.07 cm
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The frequency of a microwave signal is 9.76 GHz. What is its
wavelength?
D. 5.07 cm
E. 4.07 cm
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EM waves
A. xy-plane.
B. +z-direction.
C.
z-direction.
D.
x-direction.
E.
y-direction.
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If the electric field of an electromagnetic wave is in the +y -direction
and the magnetic field of the wave is in the +x-direction, the wave is
traveling in the
F. None of the above.
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Energy density
A. entirely in the electric field.
B. entirely in the magnetic field.
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The energy density of an electromagnetic wave in free space is
C. 1/4 in the electric field and 3/4 in the magnetic field.
D. 1/4 in the magnetic field and 3/4 in the electric field.
E. equally divided between the magnetic and the electric fields.
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Radiation Pressure: Solar sails
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Suppose a spacecraft with a mass of 2.50 ⇥ 104 kg has a solar sail
made of perfectly reflective aluminized Kapton film with an area of
2.59 ⇥ 106 m2 (about 1 square milE.. If the spacecraft is launched
into earth orbit and then deploys its sail at right angles to the
sunlight, what is the acceleration due to sunlight? (At the earth’s
distance from the sun, the pressure exerted by sunlight on an
absorbing surface is 4.70 ⇥ 10 6 Pa.)
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Radiation Pressure: Solar sails
I For a perfect reflector
I The force and pressure are given by
=
~pi
~p
=
~pf
~pi = 2~pi
F
=
P
=
F
=
ma
F
A
PA
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We will use the factor of 2 on next page
~pf
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Radiation pressure: solar sails
from previous page
=
PA
=
24.3 N
=
z}|{
2
⇥4.70 ⇥ 10
(
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F
a
=
F
m
a
=
9.72 ⇥ 10
=
6
Pa) ⇥ 2.59 ⇥ 106 m2
24.3 N
2.50 ⇥ 104 kg
4
m/s2
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Radiation pressure
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The intensity of solar radiation near the earth is 1.4 kW/m2 . What
magnitude force does this radiation exert when it strikes at right
angles to a 5.0-m2 perfectly reflecting solar panel of an artificial
satellite orbiting the earth?
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Radiation pressure
A. 7.83 ⇥ 10
5 N
C. 2.61 ⇥ 10
5 N
B. 1.63 ⇥ 10
D. 5.65 ⇥ 10
E. 0.204 ⇥ 10
5 N/m2
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If the average intensity of the sunlight in Tempe, Arizona, is
1060 W/m2 , what is the average magnitude of the force this light
exerts on a 16-m2 surface of black asphalt that totally absorbs the
light?
5 N
5 N
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Polarization
A. I
B. I /2
p
C. I / 2
D. I /16
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If unpolarized light of intensity I passes through an ideal polarizer,
what is the intensity of the emerging light?
E. 0
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Polarization
A. the beam’s direction of travel.
B. the direction of the electric field’s vibration.
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For a beam of light, the direction of polarization is defined as
C. the direction of the magnetic field’s vibration.
D. the direction that is perpendicular to both the electric and
magnetic field vectors.
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Polarization
A. 52
B. 72
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Unpolarized light is incident upon two ideal polarizing filters that do
not have their transmission axes aligned. If 19% of the light passes
through this combination, what is the angle between the
transmission axes of the two filters?
C. 60
D. 79
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Polarization
A. I0
I0
B. p
2
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Three polarizing filters are stacked with the polarizing axes of the
second and third filters oriented at 45 and 90 , respectively,
relative to the polarizing axis of the first filter. Unpolarized light of
intensity I0 is incident on the first filter. The intensity of light
emerging from the third filter is
C. I20
D. I40
E. I80
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Polarization
A. 0.780 I0
B. 0.180 I0
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Light of intensity I0 and polarized horizontally passes through three
polarizes. The first and third polarizing axes are horizontal, but the
second one is oriented 20.0 to the horizontal. In terms of I0 , what
is the intensity of the light that passes through the set of polarizers?
C. 0.442 I0
D. 0.883 I0
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AC Generator
A. 4"o
B. 2"o
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An ac generator consisting of a coil with N turns rotating at angular
speed ! in an external magnetic field B produces a maximum emf
"o .If you now decrease the number of turns in the coil to N /2 and at
the same time cause it to rotate twice as fast, what will be the new
maximum emf if you do not change any of the other quantities?
C. "o
D. "o /2
E. "o /4
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Transformers
A transformer is a device that normally
A. operates on either DC or AC.
B. operates on DC.
C. operates on AC
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Mutual inductance
A. There will be no induced current in coil B.
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Coil A is close to, but not touching, coil B. If a steady
counterclockwise 100-A current flows in coil A, what can you say
about the induced current in coil B?
B. The current in coil B will be equal to 100 A clockwise.
C. The current in coil B will be equal to 100 A counterclockwise.
D. The current in coil B will be counterclockwise and less than 100
A, but not zero.
E. The current in coil B will be clockwise and less than 100 A, but
not zero.
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Self inductance
A. 4L
B. 2L
C. L
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An ideal solenoid has a self-inductance L. If you now double its
radius and length but do not change the number of coils, what will
its self-inductance be?
D. L/2
E. L/4
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Energy in Inductors
A. True
B. False
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Inductors cannot store energy because they cannot store charge.
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Energy in Inductors
An inductor stores energy in its magnetic field.
A. True
B. False
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AC Generator
A. 7.1 Hz
B. 7.5 Hz
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You are designing an AC generator with a maximum emf of 8.0 V. If
the generator coil has 200 turns, each with a cross-sectional area of
0.030 m2 , what should be the frequency of the generator in a
magnetic field of 0.030 T?
C. 8.0 Hz
D. 44 Hz
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Transformers
A. 100 V
B. 30 V
C. 70 V
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The primary coil of an ideal transformer has 100 turns, and its
secondary coil has 400 turns. If the AC voltage applied to the
primary coil is 120 V, what voltage is present in its secondary coil?
D. 480 V
E. 400 V
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Table of Contents
Exam 1
Exam 2
Exam 3
Exam 4
Final Exam
Lecture 17
Lecture 18
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Syllabus
Lecture 19
Lecture 20
Lecture 21
Lecture 22
Lecture 23
Lecture 24
Study guide 3
Formula sheet 3
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User Instructor: Rizal F. Hariadi
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Formula sheet Exam 3
Calendar Last compiled on March 27, 2024
Envelope-open rhariadi@asu.edu
CHROME www.rizalhariadi.com
Twitter @result_hariadi
Equation sheet
Bloop
µ I
2⇡r
µ I
2R
=
=
EM wave :
Bsolenoid
=
µ nI
Magnetic flux :
B
=
BA cos
Ohm’s law:
"
=
IR
Faraday’s law:
"
=
N
=
B
t
µ
N
I
`
Current direction follows Lenz’s law
Mutual inductance:
"1
M
Self inductance:
"
=
M
i2
t
N2 B2
N1 B1
=
=
i1
i2
i
= L
t
L
=
Energy:
U
=
Transformer:
"1
"2
=
self
i
E
=
=
k
=
E
=
Emax sin(kx !t)
✓ ◆
2⇡
Emax sin
x
2⇡
!
c
=
uE
=
Radiation pressure (absorber):
P
=
Radiation pressure (reflector):
P
=
c
=
3 ⇥ 108 m/s
"
=
µ
=
=
cB
Energy density:
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Bwire
Magnetic fields:
✓
◆
=
1 B2
2µ
2⇡
T
2⇡
T
t
f
1
" E2
2
I
c
uB
2I
c
8.85 ⇥ 10
4⇡ ⇥ 10
12
7
C2 /N · m2
T · m/A
1 2
LI
2
N1
N2
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Right hand rules
E
I
B
B
I Magnetic field of a
current loop at its
center
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I
Directi
on of
propag
ation
I Magnetic field of a long
straight current carrying wire
B
Direction of
propagation
ẑ
x̂
ω
E
ŷ
ω
B
I
I
B
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