Physics 202
Spring 2010
Practice Questions for Exam 2
Note: Answer key is at the end.
1. You want to use a metal bar as a resistor. Its dimensions are 2 by 4 by 10 units. To
get the smallest resistance from this bar, you should attach leads to the two
opposite sides that have the dimensions of
A) 2 by 4 units.
B) 2 by 10 units.
C) 4 by 10 units.
D) any number of units because all connections give the same resistance.
E) None of these is correct.
2. The diagram shows the current versus voltage for a diode.
The region which has the least resistance is
A) I
B) II
C) III
D) IV
E) A diode does not have any resistance.
3. The curves on the graph represent the current versus the potential difference for
various conductors. The conductor whose behavior is described by Ohm's law is
A) 1
B) 2
C) 3
D) 4
E) None of these is correct.
4. If a current of 2.0 A is flowing from point a to point b, the potential difference
between the points is
A) 6 V
B) 8 V
C) 14 V
D) 20 V
E) 22 V
5. A wire of length L and resistance R is cut into 4 equal pieces. If the 4 pieces are now
twisted together to make a wire of length L/4, what is the new resistance of the
shorter wire combination?
A) R/16
B) R/4
C) R
D) 4R
E) 16R
6. If electric energy costs 10 cents per kilowatt-hour, how many cents does it cost to keep
a 660-W toaster in steady operation for 30 min?
A) 15 cents
B) 12 cents
C) 6.9 cents
D) 3.3 cents
E) 1.7 cents
7. You connect two similar heating coils in series on a constant-voltage line. When you
later connect them in parallel to the same line, the heat developed per minute,
compared with the former rate, is approximately
A) the same.
B) twice as great.
C) one-half as much.
D) four times as great.
E) one-fourth as much.
8. A resistor develops heat at the rate of 20 W when the potential difference across its
ends is 30 V. The resistance of the resistor is approximately
A) 45 Ω
B) 5.5 Ω
C) 30 Ω
D) 13 Ω
E) 2 Ω
9. A 6-V storage battery supplies energy to a simple circuit at the constant rate of 48 W.
The resistance of the circuit is
A) 8 Ω
B)
Ω
C) 3/2 Ω
D) 4/3 Ω
E) 3/4 Ω
10. An energy efficient light bulb uses 15 W of power for an equivalent light output of a
60 W incandescent light bulb. How much money do you save each month by using
the energy efficient light bulb instead of the incandescent light bulb for 6 hours a
day? Assume that 1 kW−hr costs 14 cents and that there are 30 days in one month.
A) $0.39
B) $0.76
C) $1.51
D) $0.57
E) $1.13
11. A motor running from a 220-V line is lifting a mass of 35 kg against Earth's gravity
at a constant speed of 6.0 m/s. If we assume 100% efficiency, the current required
is
A) 0.27 A
B) 9.4 A
C) 7.7 A
D) 3.3 A
E) 4.7 A
12. The circuit in the figure contains a battery and a resistor in series. Which of the
following statements is not true?
A) The current in the circuit is 2 A.
B) Point α is at a higher potential than point β, and Vαβ = 5 V.
C) The battery is supplying energy to the circuit at the rate of 6 W.
D) The rate of heating in the external resistor is 10 W.
E) The battery is being discharged.
13. In the circuit element shown, the current through the 6-Ω resistor is approximately
A) 1.0 A
B) 2.0 A
C) 0.40 A
D) 0.67 A
E) 1.3 A
14. In the circuit shown, the power dissipated in the 18-Ω resistor is
A) 0.15 kW
B) 98 W
C) 33 W
D) 0.33 kW
E) 47 W
15. You connect two identical resistors in series across supply lines maintained at a
constant potential difference. When you later connect them in parallel across the
same supply lines, the total current furnished by the supply lines, compared with
the former current, is
A) exactly the same.
B) twice as great.
C) one-half as much.
D) four times as great.
E) one-fourth as much.
16. You want to use three resistors in a circuit. If each of them has a resistance of 2 Ω,
the configuration that will give you an equivalent resistance of 3 Ω is
A) 1
B) 2
C) 3
D) 4
E) None of these is correct.
17. Which of the following relations among the quantities in the figure is generally
correct?
A) I1R1 = I2R2
B) I3R3 = I4R4
C) I1R1 = I4R4
D) I3R4 = I4R3
E) I1R1 + I2R2 = ε
18. Each of three identical electric heaters is rated at 1000 W when operated across 100V lines. When the three are connected in series across a 120-V line, at what rate is
electric energy converted to heat energy? (Neglect variation of resistance with
temperature.)
A) 0.48 kW
B) 1.0 kW
C) 1.2 kW
D) 3.0 kW
E) 3.6 kW
19. In the diagram above, the voltage difference between a and b is 6 V. If R1 = 25 Ω, R3
= 45 Ω, and I = 0.095 A, then find the current flowing through R2.
A) 0.026 A
B) 0.015 A
C) 0.037 A
D) 0.080 A
E) 0.070 A
20. The current I through the battery in this circuit is
A) 13 mA
B) 3.0 A
C) 15 mA
D) 0.67 A
E) None of these is correct.
21. When two identical resistors are connected in series across a battery, the total power
dissipated by them is 20 W. If these resistors are connected in parallel across the
same battery, the total power dissipated is
A) 5 W
B) 10 W
C) 20 W
D) 40 W
E) 80 W
22. The power dissipated in the 21-Ω resistor in this circuit is
A) 14 W
B) 68 W
C) 43 W
D) 13 W
E) None of these is correct.
23. What is the current through the circuit in the figure?
A) +0.83 A
B) –0.50 A
C) +0.50 A
D) +0.55 A
E) –0.92 A
24. In this circuit, the current in the 4-Ω resistor is approximately
A) zero
B) 0.63 A
C) 0.83 A
D) 1.0 A
E) 1.3 A
25. The current in the 2-Ω resistor is 2 A. What is the potential difference across the 3-Ω
resistor?
A) 4 V
B) 6 V
C) 2 V
D) 8 V
E) None of these is correct.
26. The resistance of the unknown resistor (R) is
A) 0.6 Ω
B) 2 Ω
C) 3 Ω
D) 5 Ω
E) 8 Ω
27. In this circuit, the batteries have negligible internal resistance and the ammeter has
negligible resistance. The current through the ammeter is
A) 0.30 A
B) 0.69 A
C) 2.1 A
D) 4.2 A
E) 3.6 A
28. The circuit in which the voltmeter
and the ammeter
determine the value of the unknown resistance R is
are correctly arranged to
A) 1
B) 2
C) 3
D) 4
E) 5
29. A galvanometer has an internal resistance of 200 Ω and requires a current of 5.0 mA
for full-scale deflection. What resistance should be connected in parallel with this
galvanometer so that it reads 10 A at full-scale deflection?
A) 0.10 Ω
B) 4.0 × 105 Ω
C) 400 Ω
D) 0.20 Ω
E) 2.0 Ω
30. A sensitive galvanometer has a resistance of 180 Ω and requires 2.4 µA of current to
produce a full-scale deflection. The shunt resistance needed to construct an
ammeter that gives full-scale deflection at a current of 1.0 mA is approximately
A) 4.5 Ω
B) 0.43 Ω
C) 0.22 Ω
D) 0.86 Ω
E) 1.72 Ω
31. When the ammeter
reads 7 A, the voltmeter
reads
A) 2.8 V with Y at the higher potential.
B) 2.8 V with X at the higher potential.
C) 34 V with Y at the higher potential.
D) 34 V with X at the higher potential.
E) 60 V with X at the higher potential.
32. A 1.2-µF capacitor in a flash camera is charged by a 1.5-V battery. When the camera
flashes, this capacitor is discharged through a resistor. The time constant of the
circuit is 10 ms. What is the value of the resistance?
A) 8.0 × 10–2 Ω
B) 0.12 Ω
C) 12 kΩ
D) 8.3 kΩ
E) 3.1 kΩ
33. A capacitor, initially uncharged, is connected in series to a 10-kΩ resistor and a 9.0V battery. What is the initial current in this circuit?
A) 6.0 × 10–2 A
B) 9.0 × 10–4 A
C) 5.4× 10–5 A
D) 0.90 A
E) 6.0 × 10–5 A
34. A 20-µF capacitor is charged to 200 V and is then connected across a 1000-Ω
resistor. The time constant for this circuit is approximately
A) 20 ms
B) 40 ms
C) 10 ms
D) 30 ms
E) 15 ms
35. A 0.12-µF capacitor, initially uncharged, is connected in series with a 10-kΩ resistor
and a 12-V battery of negligible internal resistance. Approximately how long does
it take the capacitor to reach 90% of its final charge?
A) 5.5 ms
B) 2.8 ms
C) 1.4 ms
D) 3.5 ms
E) 6.9 ms
36. The curve that best represents the charge on the capacitor in a charging RC circuit as
a function of time is
A) 1
B) 2
C) 3
D) 4
E) 5
37. A resistor carries a current I. The power dissipated in the resistor is P. What is the
power dissipated if the same resistor carries current 3I?
A) P
B) 3P
C) P/3
D) 9P
E) P/P
38. An uncharged capacitor and a resistor are connected in series to a battery as shown.
If ε = 15 V, C = 20 µF, and R = 4.0 × 105 Ω, the current as a function of time for
this circuit is
A) I(t) = 37.5 e0.250t µA
B) I(t) = 150 e–0.250t µA
C) I(t) = 37.5 e–0.250t µA
D) I(t) = 37.5 e–0.125t µA
E) I(t) = 300 e–0.125t µA
39. An electron (q = –1.6 × 10–19 C) is traveling east with an instantaneous velocity of
2.5 × 105 m/s when it enters a uniform magnetic field of 0.45 T that points 35°
north of east. What are the magnitude and direction of the force on the electron?
A) 1.8 × 10–14 N up
B) 1.5 × 10–14 N down
C) 1.5 × 10–14 N up
D) 1.0 × 10–14 N down
E) 1.0 × 10–14 N up
40. The left diagram shows a positively charged particle is moving with velocity v in a
magnetic field B. Using the right diagram, the direction of the magnetic force on
the particle is
A) 1
B) 2
C) 3
D) 4
E) 5
41. If the magnetic field vector is directed toward the north and a positively charged
particle is moving toward the east, what is the direction of the magnetic force on
the particle?
A) up
B) west
C) south
D) down
E) east
42. An alpha particle has a charge of +2e (e = 1.6 × 10–19 C) and is moving at right
angles to a magnetic field B = 0.27 T with a speed v = 6.15 × 105 m/s. The force
acting on this charged particle is
A) zero
B) 5.3 × 10–14 N
C) 3.3 × 105 N
D) 2.7 × 10–14 N
E) 4.8 × 105 N
43. A long straight wire parallel to the y axis carries a current of 6.3 A in the positive y
direction. There is a uniform magnetic field = 1.5 T . The force per unit
length on the wire is approximately
A) 6.3 N/m
B) –9.5 N/m
C) –6.3 N/m
D) 9.5 N/m
E) 1.5 N/m
44. A rectangular loop of wire (0.10 m by 0.20 m) carries a current of 5.0 A in a
counterclockwise direction. The loop is oriented as shown in a uniform magnetic
field of 1.5 T. The force acting on the upper 0.10-m side of the loop is
A) 1.5 N
B) 0.75 N
C) 0.50 N
D) 0.15 N
E) zero
45. An electron is traveling east with an instantaneous velocity of 3.3 × 105 m/s when it
enters a uniform magnetic field of 0.25 T that points X degrees north of east. (Take
east as to the right of the paper and north as towards the top of the paper, i.e. both
in the plane of the paper.) If the magnitude of the force on the electron is
5.5 × 10–15 N, then calculate the angle X and whether the electron moves up out of
or down into the plane of the page, or otherwise.
A) 26° and up out of the page
B) 65° and down into the page
C) 26° and down into the page
D) 65° and up out of the page
E) 65° and south in the plane of the paper

46. A positively charged
 particle moves with velocity v along the +x axis. A uniform
magnetic field B points in the negative z direction. You want to balance the
magnetic force with an electric field so that the particle will continue along a
straight line. The electric field should be in the
A) positive x direction.
B) positive z direction.
C) negative y direction.
D) negative x direction.
E) negative z direction.
47. A 7Li nucleus with a charge of +3e (e = 1.6 × 10–19 C) and a mass of 7(1.66 × 10–27)
kg and a proton with a charge of +e and a mass of 1(1.66 × 10–27) kg are both
moving in a plane perpendicular to a magnetic field . The two particles have the
same momentum. The ratio of the radius of curvature of the path of the proton (Rp)
to that of the 7Li nucleus (RLi) is
A) Rp/RLi = 3
B) Rp/RLi = 1/3
C) Rp/RLi = 1/7
D) Rp/RLi = 3/7
E) None of these is correct.
48. An alpha particle of charge +2e and mass 4(1.66 × 10–27) kg, and an 16O nucleus of
charge +8e and mass 16(1.66 × 10–27) kg have been accelerated from rest through
the same electric potential. They are then injected into a uniform magnetic field
, where both move at right angles to the field. The ratio of the radius of the path
of the alpha particle to the radius of the path of the nucleus 16O is
A) rα /rO = 1/1
B) rα /rO = 1/4
C) rα /rO = 1/8
D) rα /rO = 1/2
E) None of these is correct.
49. An electron is accelerated from rest by an electric field. After the acceleration, the
electron is injected into a uniform magnetic field of 1.27 × 10–3 T. The velocity of
the electron and the magnetic field lines are perpendicular to one another. The
electron remains in the magnetic field for 5.00 × 10–9 s. The angle between the
initial electron velocity and the final electron velocity is
A) 1.1 rad
B) 5.8 × 10–2 rad
C) 8.68 × 10–2 rad
D) 6.5 × 10–2 rad
E) 2.3 rad
50. An electron passes through a region where there is an electric field E = 4.0 × 105 V/m
and a magnetic field B = 0.090 T. The directions of the electric field, the magnetic
field, and the electron velocity are mutually perpendicular. If the electron is not
deflected from its straight-line path through these fields, its velocity must be
A) 3.6 × 104 m/s
B) 5.0 × 105 m/s
C) 2.2 × 10–7 m/s
D) 1.2 × 104 m/s
E) 4.4 × 106 m/s
51. A positively charged particle is moving through uniform fields and , which are
directed in the positive x and positive y directions, respectively. If there is no
resultant force on the particle, then its velocity is in the
A) positive x direction.
B) positive y direction.
C) negative x direction.
D) positive z direction.
E) negative z direction.
52. A beam of electrons moving at a speed of 8 × 104 m/s is undeflected when it passes
through an electric field of 5 N/C perpendicular to its path and a magnetic field that
is perpendicular to its path and also to that of the electric field. Calculate the
strength of the magnetic field.
A) 1.60 × 104 T
B) 6.25 × 10–5 T
C) 7.81 × 10–10 T
D) 3.13 × 10–5 T
E) 1.25 × 10–4 T
53. In a mass spectrometer ions of Ni with mass 9.62 ⋅ 10–26 kg and charge +2e are
accelerated through a potential difference of X volts and then deflected in a
magnetic field of 0.15 T. If the radius of curvature of the ions is 0.55 m, then
calculate the value of the potential difference X.
A) 5.7 kV
B) 274 kV
C) 137 kV
D) 11.3 kV
E) none of the above
54. A small permanent magnet is placed in a uniform magnetic field of magnitude 0.35
T. If the maximum torque experienced by the magnet is 0.50 N · m, what is the
magnitude of the magnetic moment of the magnet?
A) 1.4 A · m2
B) 0.70 A · m2
C) 0.18 A · m2
D) 2.8 A · m2
E) 0.35 A · m2
55. A circular, 20-turn coil has a radius of 5.0 cm. What is the magnitude of the
magnetic moment of the coil when it carries a current of 2.5 A?
A) 1.5 A · m2
B) 0.16 A · m2
C) 2.0 × 10–2 A · m2
D) 0.39 A · m2
E) 3.9 kA · m2
56. A circular current loop lies in the xy plane and has radius R = 10 cm. The loop has
20 turns and carries a current I = 4 A. A magnetic field of strength 0.3 T is applied
at an angle of θ = 30° to the loop. The potential energy of the magnetic dipole is
A) 0.163 J
B) 0.544 J
C) 0.314 J
D) 0.653 J
E) 0.377 J
57. A rectangle is bent on two sides at 90° so that one end lies along the xy plane while
the other end lies along the xz plane. The length of each bent portion is illustrated
on the Figure. A current I flows through the loop. The magnetic dipole of the
rectangle is
A)
B)
C)
D)
E) None of these is correct.
58. A circular 10-turn coil with a radius of 5.0 cm carries a current of 5 A. It lies in the
xy plane in a uniform magnetic field = 0.05 T + 0.12 T . The potential
energy of the system is
A) –4.72 mJ
B) –5.11 mJ
C) –6.34 mJ
D) 4.72 mJ
E) 5.11 mJ
59. The current flowing in a copper strip in the figure is 15 A.
The number density of free electrons (q = 1.6 × 10–19 C) in copper is 8.47 × 1022
electrons per cubic centimeter. The drift velocity vd is approximately
A) 3.7 × 10–2 m/s
B) 1.3 × 10–2 mm/s
C) 2.9 × 10–2 mm/s
D) 3.7 × 10–2 mm/s
E) 2.9 × 10–2 cm/s
60. The rectangular aluminum strip in the figure is in a uniform magnetic field, . The
current I is flowing perpendicular to surface 1. Positive charges will accumulate
on
A) surface 1.
B) surface 2.
C) surface 3.
D) the surface opposite surface 2.
E) none of these surfaces.
61. The top diagram shows the velocity of a positively charged particle. The direction of
the magnetic field due to the moving charge at r is best represented by
A) 1
B) 2
C) 3
D) 4
E) 5
62. A positively charged body is moving in the positive x direction as shown. The
direction of the magnetic field at the origin due to the motion of this charged body
is
A) 1
B) 2
C) 3
D) 4
E) None of these is correct, as this charged body does not create a magnetic field along
the axis of its motion.
63. At the instant the negatively charged body is at the origin, the magnetic field at point
P due to its motion is in the negative x direction. The charged body must be
moving
A) in the negative z direction.
B) in the positive y direction.
C) in the positive x direction.
D) in the negative y direction.
E) in the positive z direction.
64. What is the direction of the magnetic field around a wire carrying a current
perpendicularly into this page?
A) The field is parallel to and in the same direction as the current flow.
B) It is parallel to but directed opposite to the current flow.
C) It is counterclockwise around the wire in the plane of the page.
D) It is clockwise around the wire in the plane of the page.
E) None of these is correct.
65. A 1000-turn solenoid is 50 cm long and has a radius of 2.0 cm. It carries a current of
8.0 A. What is the magnetic field inside the solenoid near its center?
A) 2.0 × 10–2 T
B) 3.2 × 10–3 T
C) 4.0 × 10–4 T
D) 1.0 T
E) 2.0 × 10–4 T
66. Each of the figures shown is the source of a magnetic field. In which figure does the
magnetic dipole vector ( ) point in the direction of the negative x axis?
A) 1
B) 2
C) 3
D) 4
E) 5
67. In a circular loop of wire lying on a horizontal floor, the current is constant and, to a
person looking downward, has a clockwise direction. The accompanying magnetic
field at the center of the circle is directed
A) horizontally and to the east.
B) horizontally and to the north.
C) vertically upward.
D) parallel to the floor.
E) vertically downward.
68. A circular loop of wire 1.0 cm in radius carries a current of 30 A. The magnetic field
at the center of the loop is
A) 1.9 mT
B) 2.4 mT
C) 3.8 mT
D) 12 µT
E) 48 µT
69. An electron beam travels counterclockwise in a circle of radius R in the magnetic
field produced by the Helmholtz coils as shown. If you increase the current in the
Helmholtz coils, the electron beam will
A) increase its radius.
B) decrease its radius.
C) maintain the same radius.
D) reverse and travel clockwise with the same radius.
E) reverse and travel clockwise with a larger radius.
70. Two straight wires perpendicular to the plane of this page are shown in the figure.
The currents in the wires are the same. The current in M is into the page and the
current in N is out of the page. The vector that represents the resultant magnetic
field at point P is
A)
B)
C)
D)
E) None of these is correct.
71. Current-carrying wires are located along two edges of a cube with the directions of
the currents as indicated. The vector that indicates the resultant magnetic field at
the corner of the cube is
A)
B)
C)
D)
E)
72. Two long, parallel wires are spaced 1 m apart in air, and you have established a
current of 1 A in each. The magnitude of the force per unit length that each wire
exerts on the other is
A) 4πµ0
B) 2πµ0
C) µ0
D) µ0/4π
E) µ0/2π
73. Two long, straight parallel wires 9.3 cm apart carry currents of equal magnitude I.
They repel each other with a force per unit length of 5.8 nN/m. The current I is
approximately
A) 27 mA
B) 65 mA
C) 43 mA
D) 52 mA
E) 2.7 mA
74. Calculate the magnetic field and its direction at point P, which is 2.0 cm away from
the top wire and 4.0 cm from the bottom wire. Assume both wires are infinitely
long and each carries a current of 1.5 A.
A) 2.3 × 10–5 T directed OUT of the page
B) 7.5 × 10–6 T directed INTO the page
C) 2.3 × 10–5 T directed INTO the page
D) 7.5 × 10–6 T directed OUT of the page
E) 1.1 × 10–5 T directed OUT of the page
75. A long solenoid of radius 3 cm has 1100 turns per m. If the solenoid wire carries a
current of 1.5 A, then calculate the magnetic field inside the solenoid.
A) 2.1 × 10–3 T
B) 1.0 × 10–3 T
C) 1.7 × 10–4 T
D) 7.0 × 10–2 T
E) none of the above
76. The graph that best represents B as a function of r for a wire of radius R carrying a
current I uniformly distributed over its cross-sectional area is
A) 1
B) 2
C) 3
D) 4
E) 5
77. A long straight wire of radius R carries a current density J = kr A/m2 where k is a
constant. The magnetic field for r > R is (Hint: Current enclosed
.)
A) µ0kR3/3r
B) 2πµ0kR3/3r
C) 2πµ0kR2/r
D) 2πµ0kR/2
E) none of the above
78. A tightly wound solenoid 15 cm long has 350 turns and carries a current of 3.0 A. If
you ignore end effects, you will find that the value of at the center of the
solenoid when there is no core is approximately
A) 88 µT
B) 4.4 mT
C) 8.8 µT
D) 8.8 mT
E) 6.4 mT
79. A tightly wound solenoid is 15 cm long, has 350 turns, and carries a current of 3.0 A.
If you ignore end effects, you will find that the value of at the center of the
solenoid when there is an iron core of magnetization M = 1.4 × 106 A/m is
approximately
A) 11 mT
B) 8.8 mT
C) 1.8 mT
D) 7.0 mT
E) 6.2 mT
80. A long solenoid with 20 turns per centimeter has a core of iron-silicon. When the
current is 1.50 A, the magnetic field inside the core is 4.50 T. The applied field
app is approximately
A) 1.88 mT
B) 3.77 mT
C) 4.32 mT
D) 3.87 mT
E) 1.93 mT
81. A long solenoid with 20 turns per centimeter has a core of iron-silicon. When the
current is 1.50 A, the magnetic field inside the core is 4.50 T. The relative
permeability Km is approximately
A) 1800
B) 1310
C) 980
D) 556
E) 1190
82. A rectangular loop of wire (0.10 m by 0.20 m) carries a current of 5.0 A in a
counterclockwise direction. The loop is oriented, as shown, in a uniform magnetic
field of 1.5 T. The magnetic flux of is
A) 0.026 T · m2
B) 1.3 T · m2
C) 0.015 T · m2
D) 0.030 T · m2
E) 1.5 T · m2
83. A 3.0-cm by 5.0-cm rectangular coil has 100 turns. Its axis makes an angle of 55°
with a uniform magnetic field of 0.35 T. What is the magnetic flux through this
coil?
A) 3.0 × 10–4 Wb
B) 4.3 × 10–4 Wb
C) 3.0 × 10–2 Wb
D) 4.3 × 10–2 Wb
E) 5.3 × 10–2 Wb
84. A square loop of sides a lies in the yz plane with one corner at the origin. A varying
magnetic field
where k is a constant, passes through the loop. The
magnetic flux through the loop is
A) ka2
B) ka2/2
C) ka3/2
D) ka3/3
E) None of these is correct.
85. A uniform magnetic field of magnitude 0.5 T is parallel to the x axis. A square coil
of side 10 cm has 300 turns and makes an angle of 60° with the z axis as shown.
The magnetic flux through the coil is approximately
A) 0.14 Wb
B) 0.75 Wb
C) 1.5 Wb
D) 0.27 Wb
E) 0.56 Wb
86. A circular wire coil of radius 25 cm and 20 turns is sitting in a perpendicular
magnetic field of 0.2 T. If the coil is flipped over, what is the magnitude of the
change in magnetic flux through the loop?
A) 0 Wb
B) 1.6 Wb
C) 0.080 Wb
D) 0.80 Wb
E) 0.040 Wb
87. A rectangle is bent on two sides at 90° so that one end lies along the xy plane while
the other end lies along the xz plane.
The length a = 10 cm and b = 30 cm. A magnetic field of strength B = 0.1 T lies in
the yz plane and points at an angle θ = 30° with the y axis. The flux through the
rectangle is
A) 52.0 mWb
B) 30.0 mWb
C) 41.0 mWb
D) 60.0 mWb
E) None of these is correct.
88. A rectangle is bent on two sides at 90° so that one end lies along the xy–plane while
the other end lies along the xz–plane.
The length a = 10 cm and b = 30 cm. At t = 0, a magnetic field of strength B = 0.1
T lies in the yz–plane and points at an angle θ = 30° and 10 ms later the field points
in the opposite direction. The magnitude of the EMF induced in the rectangle is
A) 10.4 V
B) 6.0 V
C) 12 V
D) 8.2 V
E) None of these is correct.
89. A 3.0-cm by 5.0-cm rectangular coil has 100 turns. Its axis makes an angle of 55°
with a uniform magnetic field of 0.35 T. It requires 0.33 s to turn the coil until its
plane is perpendicular to the magnetic field. What is the (average) magnitude of
the induced EMF?
A) 0.16 V
B) 0.13 V
C) 91 mV
D) 68 mV
E) 29 mV
90. A 100-turn coil has a radius of 7.50 cm and a resistance of 50.0 Ω. At what rate must
a perpendicular magnetic field change to produce a current of 5.00 A in the coil?
A) 275 T/s
B) 134 T/s
C) 329 T/s
D) 141 T/s
E) 106 T/s
91. You place a coil that has 200 turns and a cross-sectional area of 0.050 m2 so that its
plane is normal to a field of 3.0 T. If the field is uniformly decreased to zero in
5.0 s, what is the magnitude of the EMF induced in the coil?
A) 0.15 kV
B) 0.12 kV
C) 6.0 V
D) 50 mV
E) 10 mV
92. A square coil of wire with side 8.0 cm and 50 turns sits in a uniform magnetic field
that is perpendicular to the plane of the coil. The coil is pulled quickly out of the
magnetic field in 0.2 s. If the resistance of the coil is 15 ohm and a current of 12
mA is induced in the coil, calculate the value of the magnetic field.
A) 5.6 T
B) 0.11 T
C) 7.5 × 10–3 T
D) 1.4 T
E) 9.1 T
93. A copper ring lies in the yz plane as shown. The magnet's long axis lies along the x
axis. Induced current flows through the ring as indicated. The magnet
A) must be moving away from the ring.
B) must be moving toward the ring.
C) must be moving either away from or toward the ring.
D) is not necessarily moving.
E) must remain stationary to keep the current flowing.
94. A bar magnet is dropped through a loop of copper wire as shown. Recall that
magnetic field lines point away from a north pole and toward a south pole. If the
positive direction of the induced current I in the loop is as shown by the arrows on
the loop, the variation of I with time as the bar magnet falls through the loop is
illustrated qualitatively by which of the following graphs? The time when the
midpoint of the magnet passes through the loop is indicated by C.
A) 1
B) 2
C) 3
D) 4
E) 5
95. A rectangular coil moving at a constant speed v enters a region of uniform magnetic
field from the left. While the coil is entering the field, the direction of the magnetic
force is
A) 1
B) 2
C) 3
D) 4
E) 5
96. A 25-cm long conducting rod moves at a speed of 12 m/s in a plane perpendicular to
a uniform magnetic field of magnitude 0.080 T. What is the induced potential
difference between the ends of the rod?
A) 24 V
B) 2.4 V
C) 0.24 V
D) 0.60 kV
E) 6.0 V
97. A 0.8-m-long pole rotates about a perpendicular axis at one end. As the pole rotates,
it passes through Earth's magnetic field, which has a perpendicular component of
3 × 10–5 T to the plane of rotation. If the pole rotates with a frequency of 5
revolutions per second, calculate the induced EMF across the ends of the pole.
A) 3.0 × 10–4 V
B) 1.2 × 10–5 V
C) 1.0 × 10–4 V
D) 3.8 × 10–4 V
E) 2.4 × 10–4 V
98. Two identical bar magnets are dropped from equal heights. Magnet A is dropped
over bare earth and magnet B over a metal plate. Which magnet strikes first?
A) magnet A
B) magnet B
C) both strike at the same time
D) whichever has its N pole toward the ground
E) whichever has its S pole toward the ground
99. A classic demonstration illustrating eddy currents is performed by dropping a
permanent magnet inside a conducting cylinder.
The magnet does not go into free fall. Instead it reaches terminal velocity and can
take a few seconds to drop a length of about a meter. Suppose the mass of the
magnet is 70 g and it has a terminal velocity of 10 cm/s. The length of the pipe is
80 cm. What is the magnitude of the magnetic force on the magnet when it is
falling at the terminal velocity?
A) 0.35 N
B) 0.79 N
C) 0.97 N
D) 0.69 N
E) None of these is correct.
100. How many turns are needed in a solenoid of radius 10 cm and length 20 cm for its
self-inductance to be 6.0 H?
A) 30
B) 74
C) 500
D) 550
E) 5500
Answer Key - practice questions 2 phys 202
1. C
2. D
3. C
4. A
5. A
6. D
7. D
8. A
9. E
10. E
11. B
12. C
13. D
14. B
15. D
16. D
17. B
18. A
19. A
20. E
21. E
22. E
23. C
24. D
25. A
26. B
27. B
28. C
29. A
30. B
31. C
32. D
33. B
34. A
35. B
36. D
37. D
38. D
39. D
40. A
41. A
42. B
43. B
44. B
45. C
46. C
47. A
48. D
49. A
50. E
51. D
52. B
53. D
54. A
55. D
56. E
57. B
58. A
59. D
60. B
61. D
62. D
63. A
64. D
65. A
66. E
67. E
68. D
69. B
70. D
71. B
72. E
73. D
74. B
75. A
76. C
77. A
78. D
79. A
80. B
81. E
82. A
83. C
84. C
85. B
86. B
87. C
88. D
89. C
90. D
91. C
92. B
93. B
94. A
95. C
96. C
97. A
98. A
99. D
100. E