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Physics 112
Exam 4
Summer 2006
Physics 112
Summer 2006
Exam 4
Thursday, August 3
Directions:
This exam consists of twenty six multiple-choice questions.
The questions on this test are not in order of difficulty.
You must mark all of your answers on both your test and answer sheet.
In marking the multiple choice bubble sheet use a number 2 pencil. Do not use ink. If you did
not bring a pencil, ask for one. Fill in the appropriate circles completely. If you need to change
any entry, you must completely erase your previous entry.
Carefully read each question and its five possible answers. Select one and only one answer for
each question. Choose the answer that is closest to the correct one.
You have a sheet in the back of the test that you may use for any extra rough work.
When you are finished with the exam, place all exam materials, including the bubble sheet, the
exam itself, and scratch paper that you used for the exam, in your folder and return the folder.
Good luck!
Page 1 of 9
Physics 112
Exam 4
Summer 2006
61. Three identical charges of 3.0 μC are placed at the vertices of an equilateral triangle which
measures 30 cm on a side. What is the magnitude of the electrostatic force which acts on any
one of the charges?
A) 1.6 N
B) 1.8 N
C) 2.0 N
D) 2.2 N
E) 2.4 N
62. A downward force is exerted on a negative charge. What is the direction of the electric field
at the point where the charge is located?
A) Left
B) Right
C) Upward
D) Downward
E) Not enough information to answer the question
63. The length of a wire is doubled and the radius is doubled. By what factor does the resistance
change?
A) four times as large
B) twice as large
C) half as large
D) quarter as large
E) the same
64. A heavy bus bar is 20 cm long and of rectangular cross-section, 1.0 cm × 2.0 cm. What is the
voltage drop along its length when it carries 4000 A?
(The resistivity of copper is 1.68 × 10-8 Ω∙m.)
A) 3.00 V
B) 1.20 V
C) 0.67 V
D) 0.34 V
E) 0.067 V
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Physics 112
Exam 4
Summer 2006
65. When resistors are connected in series,
A) the same power is dissipated in each one
B) the potential difference across each is the same
C) the current flowing in each is the same
D) More than one of the given answers is true
E) Non of the given answers is true
66. A battery with emf of 12 V and internal resistance 2 Ω is connected to the resistance of 22 Ω.
What is the terminal voltage of the battery?
A) 12 V
B) 11 V
C) 10 V
D) 9 V
E) 3 V
67. A 2.0-μF capacitor is charged to 12 V and then discharged through a 4.0 × 106 Ω resistor.
How long will it take for the voltage across the capacitor to drop to 3.0 V?
A) 3 s
B) 5 s
C) 8 s
D) 11 s
E) 22 s
68. An electron moves with a speed of 5.0×104m/s parallel to a uniform magnetic field of 0.20T.
What is the magnitude of the magnetic force on the electron?
A) 4.4 × 10-14 N
B) 1.6 × 10-15 N
C) 1.6 × 10-24 N
D) 2.6 × 10-24 N
E) zero
69. Two long parallel wires are placed side-by-side on a horizontal table. If the wires carry
current in the same direction,
A) one wire is lifted slightly as the other wire is forced against the table's surface.
B) both wires are lifted slightly.
C) the wires repel each other.
D) the wires attract each other.
E) there is no interaction between weirs
Page 3 of 9
Physics 112
Exam 4
Summer 2006
70. A long solenoid has 100 turns/cm and carries current 1.00A. A sphere of the radius 1.00 cm
is placed inside the solenoid. Find the magnetic flux through the sphere.
A) 1.6*10-6 T*m2
B) 1.6*10-7 T*m2
C) 4.0*10-8 T*m2
D) 8.0*10-8 T*m2
E) zero
71. A coil of 160 turns and area 0.20 m2 is placed with its axis parallel to a magnetic field of
0.40 T. The magnetic field changes from 0.40 T in the x-direction to 0.40 T in the negative xdirection in 2.0 s. If the resistance of the coil is 16 Ω, at what rate is power generated in the coil?
A) 5.0 W
B) 10 W
C) 15 W
D) 20 W
E) 25 W
72. Electromagnetic waves are
A) longitudinal
B) transverse
C) both longitudinal and transverse
D) neither longitudinal or transverse
E) electric field oscillations longitudinal, but magnetic are transverse
73. Light enters a substance from air at 30.0° to the normal. It continues through the substance at
23.0° to the normal. What would be the critical angle for this substance?
A) 51.4°
B) 45.0°
C) 36.7°
D) 12.6°
E) 10.1°
Page 4 of 9
Physics 112
Exam 4
Summer 2006
74. A person's face is 30 cm in front of a concave shaving mirror. If the image is an erect image
1.5 times as large as the object, what is the mirror's focal length?
A) 20 cm
B) 50 cm
C) 70 cm
D) 80 cm
E) 90 cm
75. The separation between adjacent maxima in a double-slit interference pattern using
monochromatic light is
A) greatest for red light.
B) greatest for green light.
C) greatest for blue light.
D) the same for all colors of light.
E) it is smallest for green light
76. White light is spread out into spectral hues by a grating. If the grating has 2000 lines per
centimeter, at what angle will red light (640 nm) appear in the first order?
A) 3.57°
B) 7.35°
C) 11.2°
D) 13.4°
E) 15.2°
77. An important reason for using a very large diameter objective in an astronomical telescope is
A) to increase the magnification.
B) to increase the resolution.
C) to form a virtual image, which is easier to look at.
D) to increase the width of the field of view.
E) to increase the depth of the field of view.
78. When light of wavelength 350 nm is incident on a metal surface, the stopping potential of the
photoelectrons is 0.500 eV. What is the work function of the metal?
A) 0.500 eV
B) 1.24 eV
C) 2.48 eV
D) 3.04 eV
E) 3.54 eV
Page 5 of 9
Physics 112
Exam 4
Summer 2006
79. An electron is accelerated through a potential difference of 150 V. What is its wavelength?
A) 0.1 nm
B) 1 nm
C) 1 mm
D) 1 cm
E) 10 cm
80. What is the energy difference between the second excited state and first excited state of an
electron in the “box” of size L=1nm?
A) 1.9 eV
B) 1.1 eV
C) 0.6 eV
D) 0.3 eV
E) 0.2 eV
81. A neutral atom has an electron configuration of 1s22s22p63s23p2. What is its atomic
number?
A) 5
B) 11
C) 14
D) 20
E) 22
82. Compared to the masses of its separate protons and neutrons, the total mass of a stable
nucleus is always
A) less
B) the same
C) greater
D) zero
E) it depends from the atomic number
83. A radioactive sample has a half-life of 10 min. What fraction of the sample is left after 40
min?
A) 1/2
B) 1/4
C) 1/8
D) 1/16
E) 1/32
Page 6 of 9
Physics 112
Exam 4
Summer 2006
84. In the fission reaction 235U + 1n → 141Ba + 92Kr + neutrons, the number of neutrons
produced is
A) zero.
B) 1
C) 2
D) 3
E) 4
85. What is the Q value for the following reaction?
7Li
1p
4He +
4He
+
=
(7.016005) (1.007825)
(4.002603) (4.002603)
A) 13.57 MeV
B) 15.37 MeV
C) 17.35 MeV
D) 18.53 MeV
E) 19.24 MeV
86. What is the wavelength of 7.0-TeV protons?
A) 550 nm
B) 750 nm
C) 5.4x10-15 m
D) 3.2x10-18 m
E) 1.8x10-19 m
Page 7 of 9
Physics 112
Exam 4
Summer 2006
Scratch Paper (intentionally left blank).
Page 8 of 9
Physics 112
Exam 4
Summer 2006
Record Sheet
You may fill in this sheet with your choices, detach it and take it with you after the exam for comparison with the
posted answers
61
71
81
62
72
82
63
73
83
64
74
84
65
75
85
66
76
86
67
77
68
78
69
79
70
80
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