Physics 112
Exam 4
Summer 2011
Name_________________
Physics 112
Summer 2011
Exam
Thursday, August 4
Directions:
This 120-minute exam consists of thirty multiple-choice questions. This test is worth
30% of your final grade. (One point is equal to 1% of the final grade.)
The questions on this test are not in order of difficulty.
You must mark all of your answers on both your test and the answer sheet.
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.
Good luck!
Page 1 of 9
Physics 112
Exam 4
Summer 2011
61. 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.
B.
C.
D.
E.
Left
Right
Upward
Downward
Not enough information to answer the question
62. A solid metal sphere of radius 2.0 cm carries a total charge of -0.1 μC. What is the
magnitude of the electric field at a distance from the sphere center of 1.0cm?
A.
B.
C.
D.
E.
0.9 x106 N/C
9.0 x106 N/C
0.3 x106 N/C
3.0 x106 N/C
0
63. A point charge of +Q is placed at the center of a square. When a second point charge
of -Q is placed at one of the square's corners, it is observed that an electrostatic force
of 2.0 N acts on the positive charge at the square's center. Now, identical charges of
-Q are placed at the other three corners of the square. What is the magnitude of the
net electrostatic force acting on the positive charge at the center of the square?
A.
B.
C.
D.
E.
0
2.8 N
4.0 N
8.0 N
16 N
64. Three positive particles of equal charge, 11.0 C, are located at the corners of an
equilateral triangle of side 15.0 cm. Calculate the magnitude and direction of the net
force on each particle.
A.
B.
C.
D.
E.
165 N
84 N
40 N
28 N
0
Page 2 of 9
Physics 112
Exam 4
Summer 2011
65. An electron (charge q = 1.60x10-19 C, and mass m = 9.11x10-31 kg) is accelerated in a
uniform field between two parallel charged plates. Potential difference between the
plates is V = 1000 V. The electron is accelerated from rest near the negative plate.
What is the speed of the electron as it reaches the positive plate?
A.
B.
C.
D.
E.
1.2 x107
1.9 x107
2.5 x107
3.2 x107
4.1 x107
m/s
m/s
m/s
m/s
m/s
66. Two resistors R1 = 5  and R2 = 10  are connected in series and are then connected
to a battery with emf, ε = 12 V. The internal resistance of the battery can be
neglected. Find the electric power delivered by the battery.
A.
B.
C.
D.
E.
1.6 W
3.2 W
6.4 W
9.6 W
12.8 W
67. What is the resistance of an electric light bulb that consumes 100 W when connected
to a 120 V outlet?
A.
B.
C.
D.
E.
1.2 Ω
100 Ω
120 Ω
144 Ω
12 k Ω
68. An electric field of 1.60 kV/m and magnetic field of 0.400 T act on a moving electron
to produce no net force. Calculate the minimum speed of the electron.
A.
B.
C.
D.
E.
2.00*103 m/s
4.00*103 m/s
6.00*103 m/s
8.00*103 m/s
2.00*102 m/s
Page 3 of 9
Physics 112
Exam 4
Summer 2011
69. A straight wire carrying a current is placed in a region containing a magnetic field.
The current flows in the +x direction. There are no magnetic forces acting on the
wire. What is the direction of the magnetic field?
A.
B.
C.
D.
E.
+x or -x direction
+y or -y direction
+z or -z direction
+y or –y or +z or -z direction
Non of the above
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.
B.
C.
D.
E.
0
1.6*10-7 T*m2
4.0*10-8 T*m2
8.0*10-8 T*m2
1.6*10-8 T*m2
71. A coil of 600 turns with area 100 cm2 is pleased in a uniform magnetic field. The
angle between the direction of the field and perpendicular to the loop is 60°. The field
changes at a rate of 0.010 T/s. What is the magnitude of the induced emf in the coil?
A.
B.
C.
D.
E.
0.09V
0.06V
0.03V
0.01V
0
72. An ideal 2.0 H inductor (i.e, one with zero resistance) has a steady current of 0.5 A
passing through it. What is the emf across the terminals of the inductor?
A.
B.
C.
D.
E.
4.0 V
2.0 V
1.0 V
0.5 V
0V
Page 4 of 9
Physics 112
Exam 4
Summer 2011
73. A circular parallel-plate capacitor with plates 4.0 cm in diameter is accumulating
charge at the rate of 3.0 mC/s at some instant of time. What is the magnitude of the
induced magnetic field at the distance 1.0 cm measured radially outward from the
center of the plates?
A.
B.
C.
D.
E.
2.0 T
0.5 T
2.0  10 8 T
1.5  10 8 T
0.5  10 8 T
74. The image formed by a convex mirror of a real object is always
A.
B.
C.
D.
E.
Real, erect, and smaller then the object
Real, inverted, and the same size as the object
Real, erect, and the same size as the object
Virtual, inverted, and larger then the object
Virtual, erect and smaller then the object
75. A glass converging lens has one flat side and another with a radius of 20 cm. What is
the focal length of the lens? ( The index of refraction of the glass in the lens is 1.50)
A.
B.
C.
D.
E.
10cm
20 cm
40 cm
60 cm
80 cm
76. Monochromatic light falls on two very narrow slits 0.048 mm apart. Successive
fringes on a screen 5.00 m away are 6.5 cm apart near the center of the pattern. What
is the wavelength of the light?
A.
B.
C.
D.
E.
620 nm
580 nm
540 nm
500 nm
460 nm
Page 5 of 9
Physics 112
Exam 4
Summer 2011
77. In order to obtain a good single slit diffraction pattern, the slit width could be:
A. /100
B. /10
C. 
D. 10
E.100
78. White light, with uniform intensity across the visible range of 400 to 700 nm, is
perpendicularly incident on a water film, of index of refraction n=1.33 and thickness
t=320nm, that is suspended in air. At what wavelength is the light reflected by the
film brightest to an observer?
A.
B.
C.
D.
E.
245nm
450nm
482nm
512nm
567nm
79. A magnifying glass with a focal length of 8.5 cm is used to read print placed at a
distance 7.5 cm. Calculate the angular magnification.
A.
B.
C.
D.
E.
2.3x
3.3x
4.3x
5.3x
6.3x
80. A near-sighted person has a far point of 20 cm. What lens (in diopters) will allow this
person to see distant objects clearly? Assume that the lens is 2.0 cm from the eye
(typical for eyeglasses)
A) + 5.6 D
B) - 5.6 D
C) + 0.056 D
D) - 0.056 D
E) -5.0 D
Page 6 of 9
Physics 112
Exam 4
Summer 2011
81. When light of wavelength 350 nm is incident on a metal surface, the stopping
potential of the photoelectrons is 0.500 V. What is the threshold frequency?
A) 3.47 × 1014 Hz
B) 3.74 × 1014 Hz
C) 4.73 × 1014 Hz
D) 7.36 × 1014 Hz
E) 9.21 × 1014 Hz
82. 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
83. In making a transition from state n = 1 to state n = 2, the hydrogen atom must
A) absorb a photon of energy 10.2 eV.
B) emit a photon of energy 10.2 eV.
C) absorb a photon of energy 13.6 eV.
D) emit a photon of energy 13.6 eV.
E) absorb a photon of energy 27.2 eV.
84. An electron has a wavelength of 0.123 nm. What is its energy in eV? (This energy is
not in the relativistic region.)
A) 20 eV
B) 60 eV
C) 80 eV
D) 100 eV
E) 120 eV
85. The probability of finding an electron in a hydrogen atom is directly proportional to
its
A) energy
B) momentum
C) angular momentum
D) wave function
E) square of the wave function
Page 7 of 9
Physics 112
Exam 4
Summer 2011
86. A neutral atom has an electron configuration of 1s22s22p6. If a neutral atom holds
one additional electron, what is the ground state configuration?
A) 1s22s22p63s1
B) 1s22s22p7
C) 1s22s32p6
D) 1s32s22p6
E) none of the given answers
87. The binding energy per nucleon
A) increases steadily as we go to heavier elements.
B) decreases steadily as we go to heavier elements.
C) is approximately constant throughout the periodic table, except for very light nuclei.
D) has a maximum near iron in the periodic table.
E) is a periodic function
88. 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) could be less or grater
89. If the half-life of a material is 45 years, how much will be left after 100 years?
A) more than 1/2
B) less than 1/2 but more then 1/3
C) less than 1/3 but more than 1/4
D) less than 1/4
E) zero
90. What is the Q-value of the following reaction?
14N +
4He =
1p
17O
+
(14.003074)
(4.002603) (1.007825)
(16.999131)
A) 1.191 MeV
B) -1.191 MeV
C) 1.279 × 10-3 MeV
D) -1.279 × 10-3 MeV
E) zero
Page 8 of 9
Physics 112
Exam 4
Summer 2011
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
87
68
78
88
69
79
89
70
80
90
Page 9 of 9