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Physics 112
Exam 2
Summer 2016
Name_________________
Physics 112
Summer 2016
Exam 2
Monday, July 11
Directions:
This 60-minute exam consists of twenty multiple-choice questions. This test is worth 20% 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 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 7
Physics 112
Exam 2
Summer 2016


21. Positive charge q is moving with velocity v in the magnetic field B as shown below (with


vectors v and B on the surface of the page). What is the direction of the magnetic force?

v
q
A)
B)
C)
D)
E)


Parallel to v

Parallel to B


Exactly between v and B
Into the page
Out of the page

B
22. A positively charged particle is moving in a magnetic field. What is the angle between the
velocity of the charge and the direction of the magnetic field if the magnetic force on the particle
is zero?
A)
B)
C)
D)
E)
90°
45°
30°
0
Magnetic force cannot be zero if the speed of the particle and the magnetic field are not zero.
23. Alpha particles of charge q  2e and mass m  6.6  10 27 kg are emitted from a radioactive
source at a speed of 1.6 107 m s . What magnetic field strength would be required to bend them
into a circular path of radius r  0.25 m?
A)
B)
C)
D)
E)
5.3 T
4.3 T
3.3T
2.3 T
1.3 T
24. If a bar magnet is divided into two equal pieces,
A) the north and south poles are separated
B) two magnets result
C) the magnetic properties are destroyed
D) an electric field is created
E) none of the above
Page 2 of 7
Physics 112
Exam 2
Summer 2016
25. An airplane with a wing span of 60 m flies horizontally at a location where the downward
component of the Earth's magnetic field is 6.0 × 10-5 T. Find the magnitude of the induced emf
between the tips of the wings when the speed of the plane is 225 m/s.
A)
B)
C)
D)
E)
0.41 V
0.61 V
0.81 V
1.2 V
1.4 V
26. A wire carries a current of 10 A in a direction of 30° with respect to the direction of a 0.30-T
magnetic field. Find the magnitude of the magnetic force on a 0.50-m length of the wire.
A) 0.75 N
B) 1.5 N
C) 3.0 N
D) 6.0 N
E) zero
27. A circular loop of wire of radius 0.50 m is in a uniform magnetic field of 0.30 T. The current
in the loop is 2.0 A. What is the magnetic torque when the plane of the loop is perpendicular to
the magnetic field?
A)
B)
C)
D)
E)
0.73 m∙N
0.52 m∙N
0.47 m∙N
0.41 m∙N
zero
28. What is the strength of a magnetic field 5.0 cm from a long straight wire carrying 4.0 A of
current?
A)
B)
C)
D)
E)
3.8∙10-6 T
4.9∙10-6 T
1.6 ∙10-5 T
4.7∙10-5 T
5.1∙10-5 T
Page 3 of 7
Physics 112
Exam 2
Summer 2016
29. Two long parallel wires carry currents of 5.0 A and 8.0 A in the opposite direction. The
wires are separated by 0.30 m. Find the magnetic force per unit length between the two wires.
A)
B)
C)
D)
E)
2.7∙10-5 N repulsive
7.2∙10-5 N repulsive
2.7∙10-5 N attractive
7.2∙10-5 N attractive
zero
30. A long solenoid has 100 turns/cm and carries a current of 1.00A. A sphere of radius 1.00 cm
is placed inside the solenoid. Find the magnetic flux through 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
31. What is the direction of the induced current in the circular loop due to the increasing current
shown below?
I increasing
A)
B)
C)
D)
E)
Counterclockwise
Clockwise
The direction of the current is periodically changing
Induced current is equal to zero
There is not enough information to answer the quastion
32. An AC generator consists of 100 turns (loops) of wire with total resistance 12 Ω. The area of
each loop is 0.090 m2. The loops rotate in a magnetic field of 0.50 T at a constant frequency of
60 Hz. Find the maximum induced emf.
A)
B)
C)
D)
E)
0.27 kV
0.54 kV
1.7 kV
3.4 kV
5.1 kV
Page 4 of 7
Physics 112
Exam 2
Summer 2016
33. Doubling the number of loops of wire in a coil produces what kind of change on the induced
emf, assuming all other factors remain constant?
A)
B)
C)
D)
E)
The induced emf increases 4 times
The induced emf increases 2 times
The induced emf decreases 2 times
The induced emf decreases 4 times
The induced emf remains the same
34. A simple RL circuit contains a 6.0-Ω resistor and an 18-H inductor. What is this circuit's
time constant?
A)
B)
C)
D)
E)
108 s
3.0 s
0.33 s
0.20 s
0.11 s
35. A 6 V battery is connected to coil 1 of the transformer shown in the figure below. Coil 2 has
twice as many turns as coil 1. What is the voltage drop across coil 2?
A)
B)
C)
D)
E)
12 V
6V
3V
2V
0
1
2
36. The magnetic field inside an air-filled solenoid 36 cm long and 2.0 cm in diameter is 0.80 T.
Approximately how much energy is stored in this field?
A)
B)
C)
D)
E)
5J
11 J
18 J
21 J
29 J
Page 5 of 7
Physics 112
Exam 2
Summer 2016
37. What is the current through a 3.1-mH coil due to a 12-V, 60.0 Hz source?
A)
B)
C)
D)
E)
0.94 A
2.5 A
6.4 A
10 A
15 A
38. 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 in 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 at this instant?
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
39. An electromagnetic wave in vacuum is moving in +y direction. At time t=0 and at position
(x,y,z)=(0,0,0), the electric field is pointing in the +z direction. In what direction is the magnetic
field pointing at that time and position?
A)
B)
C)
D)
E)
+x
–x
+y
–y
+z
40. If the magnetic field in a traveling EM wave has a peak magnitude of 17.5 nT, what is the
peak magnitude of the electric field?
A)
B)
C)
D)
E)
zero
1.75 V/m
3.50 V/m
5.25 V/m
7.00 V/m
Page 6 of 7
Physics 112
Exam 2
Summer 2016
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
21
31
22
32
23
33
24
34
25
35
26
36
27
37
28
38
29
39
30
40
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