PHYS2002 – Practice Exam 2 (Ch. 22, 24 - 26) Questions
and Answers-Louisiana State University
1. The figure below shows the top view of two circular, conducting loops of wire
lying on a flat surface with concentric centers. The larger diameter loop contains
a switch and a battery. The smaller loop contains no switch or battery. Which of
the following best describes the induced current that flows in the smaller loop,
once the switch in the larger loop is closed?
switch
−
+
A. No current flows in the smaller loop.
B. A current flows cw in the smaller loop forever.
C. A current flows ccw in the smaller loop forever.
D. A current flows cw in the smaller loop only for a short period right after the
switch is closed.
E. A current flows ccw in the smaller loop only for a short period right after the
switch is closed.
2. In the figure below, a conducting rod of length 0.75 m is being pulled to the right
at a constant speed of v = 15 m/s along two frictionless, conducting rails. The rod
and the rails form a complete circuit with a resistor R = 6.0 . A uniform
magnetic field B = 4.5 T exists everywhere directed into the page. What is the
direction of the induced current through the resistor, and what is the power
dissipated in the resistor?
C
A. The current flows from C to D, 8.4 W.
B. The current flows from D to C, 8.4 W.
C. The current flows from C to D, 430 W.
D. The current flows from D to C, 430 W. D
E. The current flows from C to D, 38 W.
3. An 80-turn circular coil of radius 0.05 m and resistance of 30 sits in a region of
space with a uniform magnetic field that passes perpendicularly through its
surface. At what rate must the magnitude of the magnetic field change so that a
current of 4.0 A is produced in the coil?
A. 15,300 T/s
B. 190 T/s
C. 120 T/s
D. 9.5 T/s
E. 1.5 T/s
, 4.
9. The primary side of a step-up transformer has 250 turns and is connected to a
120-V rms AC line. What is the peak voltage produced on the secondary side of
the transformer if the secondary coil has 3000 turns?
A. 10 V
B. 14 V
C. 1018 V
D. 1440 V
E. 2036 V
5. In the figure below unpolarized light is incident on polarizer A and the light then
passes through polarizers B and C before exiting the optical system to the right.
Polarizer A is aligned vertically, polarizer B is aligned at an angle θ with respect
to the vertical axis and polarizer C is aligned horizontally or 90 with respect to
polarizer A. Which value of θ (i.e. the angle of polarizer B) allows the maximum
intensity of light to pass through the optical system?
A. 0o
B. 45o
C. 60o
D. 90o
E. No light is transmitted through the system.
6. Fleet Admiral Pike on the starship USS Excalibur, which has suffered battle
damage due to an encounter with a Romulan warship, is attempting to contact
Captain Kirk on the starship USS Enterprise in order to warn him about the
presence of the Romulan ship. Due to the battle damage Admiral Pike must use
an old style FM radio transmitting at a frequency of 100 MHz in order to contact
Kirk. The USS Excalibur is traveling at 15% of the speed of light and the USS
Enterprise is following behind at 20% of the speed of light. At what frequency
must Lieutenant Uhura tune the FM radio on board the USS Enterprise in order to
receive Pike’s critical communication before the ship is destroyed?
A. 95 MHz
B. 105 MHz
C. 115 MHz
D. 120 MHz
E. 100 MHz
7. A quarter-wave antenna is attached to a radio receiver and tuned so that radio
waves with a wavelength that is four times as long as the antenna are optimally
received by the radio. What would be the minimum length of such an antenna for
the radio to have its best reception at 5 MHz?
A. 9m
B. 13 m
C. 60 m
D. 30 m
E. 15 m
and Answers-Louisiana State University
1. The figure below shows the top view of two circular, conducting loops of wire
lying on a flat surface with concentric centers. The larger diameter loop contains
a switch and a battery. The smaller loop contains no switch or battery. Which of
the following best describes the induced current that flows in the smaller loop,
once the switch in the larger loop is closed?
switch
−
+
A. No current flows in the smaller loop.
B. A current flows cw in the smaller loop forever.
C. A current flows ccw in the smaller loop forever.
D. A current flows cw in the smaller loop only for a short period right after the
switch is closed.
E. A current flows ccw in the smaller loop only for a short period right after the
switch is closed.
2. In the figure below, a conducting rod of length 0.75 m is being pulled to the right
at a constant speed of v = 15 m/s along two frictionless, conducting rails. The rod
and the rails form a complete circuit with a resistor R = 6.0 . A uniform
magnetic field B = 4.5 T exists everywhere directed into the page. What is the
direction of the induced current through the resistor, and what is the power
dissipated in the resistor?
C
A. The current flows from C to D, 8.4 W.
B. The current flows from D to C, 8.4 W.
C. The current flows from C to D, 430 W.
D. The current flows from D to C, 430 W. D
E. The current flows from C to D, 38 W.
3. An 80-turn circular coil of radius 0.05 m and resistance of 30 sits in a region of
space with a uniform magnetic field that passes perpendicularly through its
surface. At what rate must the magnitude of the magnetic field change so that a
current of 4.0 A is produced in the coil?
A. 15,300 T/s
B. 190 T/s
C. 120 T/s
D. 9.5 T/s
E. 1.5 T/s
, 4.
9. The primary side of a step-up transformer has 250 turns and is connected to a
120-V rms AC line. What is the peak voltage produced on the secondary side of
the transformer if the secondary coil has 3000 turns?
A. 10 V
B. 14 V
C. 1018 V
D. 1440 V
E. 2036 V
5. In the figure below unpolarized light is incident on polarizer A and the light then
passes through polarizers B and C before exiting the optical system to the right.
Polarizer A is aligned vertically, polarizer B is aligned at an angle θ with respect
to the vertical axis and polarizer C is aligned horizontally or 90 with respect to
polarizer A. Which value of θ (i.e. the angle of polarizer B) allows the maximum
intensity of light to pass through the optical system?
A. 0o
B. 45o
C. 60o
D. 90o
E. No light is transmitted through the system.
6. Fleet Admiral Pike on the starship USS Excalibur, which has suffered battle
damage due to an encounter with a Romulan warship, is attempting to contact
Captain Kirk on the starship USS Enterprise in order to warn him about the
presence of the Romulan ship. Due to the battle damage Admiral Pike must use
an old style FM radio transmitting at a frequency of 100 MHz in order to contact
Kirk. The USS Excalibur is traveling at 15% of the speed of light and the USS
Enterprise is following behind at 20% of the speed of light. At what frequency
must Lieutenant Uhura tune the FM radio on board the USS Enterprise in order to
receive Pike’s critical communication before the ship is destroyed?
A. 95 MHz
B. 105 MHz
C. 115 MHz
D. 120 MHz
E. 100 MHz
7. A quarter-wave antenna is attached to a radio receiver and tuned so that radio
waves with a wavelength that is four times as long as the antenna are optimally
received by the radio. What would be the minimum length of such an antenna for
the radio to have its best reception at 5 MHz?
A. 9m
B. 13 m
C. 60 m
D. 30 m
E. 15 m
