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Physics 112
Exam 2
Spring 2006
Name_________________
Physics 112
Spring 2006
Exam 2
Wednesday, Mar 8
Directions:
This 50-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 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.
Be sure to write you name on every sheet.
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 8
Physics 112
Exam 2
Spring 2006
21. 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

22. A current-charring circular coil with a magnetic moment  is in uniform magnetic

field B . The maximum magnitude of the torque on the coil in the magnetic field


occurs when the angle between  and B is
A.
B.
C.
D.
E.
0
45°
90°
135°
180°
23. Two long thin straight parallel wires are 4.0 cm apart. The two wires each carry the
same current 10 A in the same direction. Find the (net) magnetic field at a point
midway between the two wires.
A. 2 104 T
B. 4  10 4 T
C. 8  10 4 T
D. 0.2 T
E. 0
24. 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
Page 2 of 8
Physics 112
Exam 2
Spring 2006
25. A 1.00 A current in an ideal solenoid of length 0.500 m produces a magnetic field of
magnitude 2.00 mT at the center of the solenoid. What is the number of turns in the
solenoid?
A.
B.
C.
D.
E.
400
800
1600
2400
3200
26. 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
27. 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
28. A generator rotates at 85 Hz in a magnetic field of 0.03 T. It has 1000 turns and
produces an rms voltage of 150 V. What is the area of each turn of the coil?
A.
B.
C.
D.
E.
2.6  10 2 m 2
1.3 10 2 m 2
0.7  10 2 m 2
5.0  10 3 m 2
2  10 3 m 2
Page 3 of 8
Physics 112
Exam 2
Spring 2006
29. A uniform magnetic field B = 0.5 T is perpendicular to the area bounded by the U
shaped conductor and a movable metal rod of length l = 0.1 m. The rod is moving
along the conductor at a speed v = 3m/s. What is the magnitude of the induced emf?
A.
B.
C.
D.
E.
0.05V
0.15V
0.3V
1.5V
0
30. Two tightly wound solenoid shave the same length and circular cross-sectional area.
They use wires made from the same material, but solenoid 1 uses wire that is half as
thick as solenoid 2. What is the ratio of their inductances?
A.
B.
C.
D.
E.
16
8
4
2
1
31. 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
32. The magnetic field inside an air-field solenoid 25 cm long and 2.0 cm in diameter is
0.80 T. Approximately how much energy is stored in the field?
A.
B.
C.
D.
E.
5J
10 J
15 J
20 J
25 J
Page 4 of 8
Physics 112
Exam 2
Spring 2006
33. A circular parallel-plate capacitor with plates 4.0cm 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
34. 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 pointing the magnetic field at that time and position?
A.
B.
C.
D.
E.
+x
–x
+y
–y
+z
35. Light is incident on an equilateral glass prism at a 45.0° angle to one face. Calculate
the angle at which light emerges from the opposite face. Assume that index of
refraction is 1.52.
A.
B.
C.
D.
E.
24°
34°
44°
54°
64°
Page 5 of 8
Physics 112
Exam 2
Spring 2006
36. The image formed by a plane 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
Virtual, inverted, and larger then the object
Virtual, erect and the same size as the object
Real, erect, and the same size as the object
37. 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
38. An object 0.60 cm tall is placed 16.5 cm to the left of the vertex of a concave
spherical mirror having a radius of curvature 22.0cm. What is the size of the image?
A.
B.
C.
D.
E.
1.0 cm
1.2 cm
2.5 cm
6.0 cm
9.4 cm
39. A thin symmetric lens provides an image of a fingerprint with a magnification +0.2
when the fingerprint is 1 cm farther from the lens than the focal point of the lens.
What is the type of the image, and what is the type of the lens?
A.
B.
C.
D.
E.
Real, converging
Real, diverging
Virtual, converging
Virtual, diverging
Non of these
40. 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
Page 6 of 8
Physics 112
Exam 2
Spring 2006
Scratch Paper (intentionally left blank).
Page 7 of 8
Physics 112
Exam 2
Spring 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
21
31
22
32
23
33
24
34
25
35
26
36
27
37
28
38
29
39
30
40
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