Download White light is spread out into spectral hues by a grating

Physics 112
Exam 4
Summer 2015
Physics 112
Summer 2015
Exam 4
Thursday, August 6
Directions:
This 120-minute exam consists of thirty two 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 the 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.
When you are finished with the exam, return the bubble sheet, the exam itself, and scratch paper
that you used for the exam.
Good luck!
Page 1 of 11
Physics 112
Exam 4
Summer 2015
61. Two parallel plates, separated by 0.20 m, are connected to a 12-V battery. What is the
potential difference between the following two points inside the capacitor: one point is 0.10 m
from the positive plate, and another point is 0.050 m from the positive plate?
A)
B)
C)
D)
E)
2.4 V
3.0 V
4.8 V
6.0 V
7.2
62. A copper 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)
B)
C)
D)
E)
3.00 V
1.20 V
0.67 V
0.34 V
0.067 V
63. When resistors are connected in series,
A)
B)
C)
D)
E)
The same power is dissipated in each one
The potential difference across each is the same
The current flowing in each is the same
More than one of the given answers are true
None of the given answers are true
64. A battery with emf of 12 V and an internal resistance of 2 Ω is connected to a resistance of
22 Ω. What is the terminal voltage of the battery?
A)
B)
C)
D)
E)
12 V
11 V
10 V
9V
3V
Page 2 of 11
Physics 112
Exam 4
Summer 2015
65. 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)
B)
C)
D)
E)
1.6 N
1.8 N
2.0 N
2.2 N
2.4 N
66. 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
67. A solid metal sphere of radius 4.0 cm carries a total charge of 3.5μC. What is the magnitude
of the electric field at a distance 2.0 cm from the sphere’s center?
A)
B)
C)
D)
E)
3.3 105 N / C
3.3  10 4 N / C
8.7  10 5 N / C
8.7 10 4 N / C
zero
68. What will happen with the capacitance of a parallel plate capacitor if the distance between its
plates is doubled while all other parameters of the capacitor remain the same?
A)
B)
C)
D)
E)
Increases 4 times
Increases 2 times
Decreases 2 times
Decreases 4 times
Remains the same
Page 3 of 11
Physics 112
Exam 4
Summer 2015
69. Two long parallel wires carry currents of 20 A and 5.0 A in opposite directions. The wires
are separated by 0.20 m. What is the magnetic field midway between the two wires?
A)
B)
C)
D)
E)
1.0 × 10-5 T
3.0 × 10-5 T
4.0 × 10-5 T
5.0 × 10-5 T
zero
70. A long, thin wire carries current of 1.00 A. A sphere of the radius 1.00 cm is placed so that
its center is 2.00 cm from the wire. Find the magnetic flux through the surface of the sphere.
A)
B)
C)
D)
E)
1.6*10-6 T*m2
1.6*10-7 T*m2
4.0*10-8 T*m2
8.0*10-8 T*m2
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 positive x-direction to 0.40 T in the
negative x-direction in 2.0 s. If the resistance of the coil is 16 Ω, at what rate is power generated
in the coil?
A)
B)
C)
D)
E)
5.0 W
10 W
15 W
20 W
25 W
72. Electromagnetic waves are
A)
B)
C)
D)
E)
Longitudinal
Transverse
Both longitudinal and transverse
Neither longitudinal or transverse
Electric field oscillations longitudinal, but magnetic are transverse
Page 4 of 11
Physics 112
Exam 4
Summer 2015
73. What is the maximum number of 100-W light bulbs you can connect in parallel in a 120-V
circuit without tripping a 20-A circuit breaker? (This breaker can sustain 20 A.)
A)
B)
C)
D)
E)
11
17
24
27
30
74. 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)
B)
C)
D)
E)
3s
5s
8s
11 s
22 s
75. 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)
B)
C)
D)
E)
4.4 × 10-14 N
1.6 × 10-15 N
1.6 × 10-24 N
2.6 × 10-24 N
zero
76. Two long parallel wires are placed side-by-side on a horizontal table. The wires carry
current in the same direction. What happens with the wires?
A)
B)
C)
D)
E)
One wire is lifted slightly as the other wire is forced against the table's surface
Both wires are lifted slightly
The wires repel each other
The wires attract each other
There is no interaction between wires
Page 5 of 11
Physics 112
Exam 4
Summer 2015
77. An important reason for using a very large diameter objective in an astronomical telescope is
A)
B)
C)
D)
E)
To increase the magnification
To increase the resolution
To form a virtual image
To form a real image
To increase the width of the field of view
78. The work function for a certain sample is 2.1 eV. What is the stopping potential for electrons
ejected from the sample by a 7.0*1014 Hz electromagnetic radiation?
A)
B)
C)
D)
E)
0.2 V
0.4 V
0.6 V
0.8 V
1.0 V
79. Which has more energy, a photon of:
A)
B)
C)
D)
E)
Red light
Yellow light
Green light
Blue light
All have the same energy
80. An electron is accelerated through a potential difference of 150 V. What is its wavelength?
A)
B)
C)
D)
E)
0.1 nm
1 nm
1 mm
1 cm
10 cm
Page 6 of 11
Physics 112
Exam 4
Summer 2015
81. 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)
B)
C)
D)
E)
51.4°
45.0°
36.7°
12.6°
10.1°
82. Convex spherical mirrors produce images which are
A)
B)
C)
D)
E)
Always real and smaller than the actual object
Always virtual and smaller than the actual object
Always real and larger than the actual object
Always virtual and larger than the actual object
Could be real or virtual and larger or smaller than the actual object, depending on the
placement of the object
83. The separation between adjacent maxima in a double-slit interference pattern using
monochromatic light is
A)
B)
C)
D)
E)
Greatest for red light
Greatest for green light
Greatest for blue light
The same for all colors of light
It is smallest for green light
84. White light is spread out into spectrum by a grating. If the grating has 2000 lines per
centimeter, at what angle will red light (640 nm) appear in the first order bright fringe?
A)
B)
C)
D)
E)
3.57°
7.35°
11.2°
13.4°
15.2°
Page 7 of 11
Physics 112
Exam 4
Summer 2015
85. A radioactive sample has a half-life of 10 min. What fraction of the sample is left after 40
min?
A)
B)
C)
D)
E)
1/2
1/4
1/8
1/16
1/32
86. In the fission reaction 235U + 1n → 141Ba + 92Kr + neutrons, the number of neutrons
produced is
A)
B)
C)
D)
E)
zero
1
2
3
4
87. What is the Q value for the following reaction?
7Li
1p
4He +
4He
+
=
(7.016005) (1.007825)
(4.002603) (4.002603)
A)
B)
C)
D)
E)
13.57 MeV
15.37 MeV
17.35 MeV
18.53 MeV
19.24 MeV
88. What is the wavelength of 7.0-TeV protons?
A)
B)
C)
D)
E)
550 nm
750 nm
5.4x10-15 m
3.2x10-18 m
1.8x10-19 m
Page 8 of 11
Physics 112
Exam 4
Summer 2015
89. An electron moves in a straight line with a constant speed v=1.10x106 m/s which has been
measured to a precision of 0.10%. What is the maximum precision with which its position could
be simultaneously measured?
A)
B)
C)
D)
E)
10 nm
110 nm
210 nm
320 nm
540 nm
90. What is the energy difference between the first excited state and the ground state of an
electron in the “box” of size L=1nm?
A)
B)
C)
D)
E)
1.9 eV
1.1 eV
0.6 eV
0.3 eV
0.2 eV
91. A neutral atom has an electron configuration of 1s22s22p63s1. What is its atomic number?
A)
B)
C)
D)
E)
4
8
11
20
22
92. More massive nuclei require extra neutrons in order to be stable. Why?
A)
B)
C)
D)
E)
To overcome the Coulomb repulsion of the protons
To overcome the Coulomb attraction of the protons
To overcome gravitational attraction of the protons
More light nuclei require extra neutrons in order to be stable
There is no interaction between protons
Page 9 of 11
Physics 112
Exam 4
Summer 2015
Record Sheet
61
71
81
91
B) 3.0 V
B) 10 W
A) 51.4°
C) 1.1 eV
62
72
82
92
E) 0.067 V
B) Transverse
B) Always virtual and A) To overcome the
smaller than the
Coulomb repulsion of
actual object
the protons
63
73
83
C) The current
flowing in each is the
same
C) 24
A) Greatest for red
light
64
74
84
B) 11 V
D) 11 s
B) 7.35°
65
75
85
A) 1.6 N
E) zero
D) 1/16
66
76
86
C) Upward
D) The wires attract
each other
D) 3
67
77
87
E) zero
B) To increase the
resolution
C) 17.35 MeV
68
78
88
C) Decreases 2 times
D) 0.8 V
E) 1.8x10-19 m
69
79
89
D) 5.0 × 10-5 T
D) Blue light
B) 110 nm
70
80
90
E) zero
A) 0.1 nm
B) 1.1 eV
Page 10 of 11
Physics 112
Exam 4
Summer 2015
Record Sheet
61
71
81
91
62
72
82
92
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 11 of 11