Chapters 21 - 29
PHYS 2426 - Brooks
This practice test is similar to the actual test. The class test will consist of about
35 questions designed to be completed in about 2 hours. This practice test does
not cover every single concept that may be on the actual class test. An answer
key is included, but there are no solutions to the problems. Students need to
work out all solutions on their own.
Select the response that best answers the given statement.
1.
A metal cylinder of radius 2.0 mm is concentric with another
metal cylinder of radius 5.0 mm. If the space between the
cylinders is filled with air and the length of the cylinders
is 50 cm, the capacitance of the arrangement is
a. 30 pF
b. 60 pF
c. 11 pF
d. 22 pF
2.
To produce higher voltages, the cells of a battery are
connected in series. True or false?
a. True
b. False
3.
If in the diagram I1 = 2A, what is the current through the
2 Ω resistor?
a.
b.
c.
d.
2
2
5
5
A,
A,
A,
A,
up
down
up
down
4.
If a molecule of oxygen in air has a translational kinetic
energy of 1/40 eV, what is its speed?
a. 390 m/s
b. 550 m/s
c. 2200 m/s
d. 15000 m/s
5.
The mass of an electron is 9.11 x 10-31 kg. The mass of one
(negative) coulomb of electrons is
a. 1 gram
b. 5.69 x 10-12 kg
c. 5.48 x 10-7 kg
d. 2.7 x 1019 /cm3
6.
If the net flux through a closed surface is zero, then there
can be no charge or charges within that surface. True or
false?
a. True
b. False
7.
The electron volt is a unit for
a. potential
b. gradient
c. electron potential
d. energy
8.
A 6-Ω resistor, an 8-Ω resistor, and a 24-Ω resistor are
connected together. What is the minimum resistance that can
be produced using all three resistors?
a. 3 Ω
b. 4 Ω
c. 7 Ω
d. (1/24) Ω
9.
The fatter a given length of wire is the higher its
resistance will be. True or false?
a. True
b. False
10. A 1 mF, a 2 mF, and a 3 mF capacitor are connected in series,
the combination being connected across a 9 volt battery. The
capacitor with the greatest charge on it is
a. the 1 mF
b. the 2 mF
c. the 3 mF
d. neither since they all have the same charge
11. An ideal ammeter is one that does not change the behavior of
a circuit when it is properly used to measure current. The
internal resistance of such a meter is
a. 0 Ω
b. the same resistance as the circuit
c. infinite
d. dependent on the circuit
12. The peak voltage of a 120-V ac line is
a. 220 V
b. 170 V
c. 120 V
d. 110 V
13. Parallel plate capacitor #1 has twice the plate area and
twice the plate separation of capacitor #2. The capacitance
of the second capacitor is
a. the same as the first
b. double the first
c. quadruple the first
d. eight times the first
14. If in the diagram I1 = 2A, what is V2?
a.
b.
c.
d.
10
22
30
34
V
V
V
V
15. If the voltage between the plates of a parallel plate
capacitor is doubled, the capacitance of the capacitor
a. is halved
b. remains the same
c. is doubled
d. quadruples
16. If the potential is given by V = xy - 3z-2, then the electric
field has a y-component
a. x
b. y
c. x + y
d. x + y - 6z-3
17. An oxygen ion, O++, is enclosed in a gaussian surface. The
flux leaving that surface is
a. 3.2 x 10-19 Nm2/C
b. 3.6 x 10-8 Nm2/C
c. 8.86 x 10-12 Nm2/C
d. 2 Nm2/C
18. A charge Q is uniformly distributed throughout a
nonconducting sphere of radius R. What is the magnitude of
the electric field at a distance R/2 from the center of the
sphere?
a. Q/2πεoR2
b. Q/4πεoR2
c. Q/8πεoR2
d. Q/16πεoR2
19. What is the resistance between points a and b?
a.
b.
c.
d.
3Ω
8.2 Ω
8.25 Ω
9Ω
20. When static equilibrium is established for a charged
conductor, the electric field just inside the surface of the
conductor is
a. equal to the field outside
b. equal to the perpendicular component of the field outside
c. opposite to the field outside
d. zero
21. If an electron is accelerated from rest through a potential
difference of 25,000 volts in a color television picture
tube, its kinetic energy will be
a. 4.0 x 10-15 J
b. 4.0 x 10-5 J
c. 2.5 x 104 J
d. 1.6 V
22. Three equal charges are located at the corners of an
equilateral triangle. If each of the charges were to be
doubled, then the resulting force on each of the charges
a. remains the same
b. doubles
c. triples
d. quadruples
23. The voltage between two parallel plates separated by a
distance of 3.0 cm is 120 V. The electric field between the
plates is
a. 4000 V/m
b. 2000 V/m halfway between the plates
c. up to 4000 V/m depending on position
d. 3.6 V/m
24. A 1200-W toaster draws more current than a 1000-W toaster.
True or false?
a. True
b. False
25. If a point charge is located at the center of a cylinder and
the electric flux leaving one end of the cylinder is 20% of
the total flux leaving the cylinder, what portion of the flux
leaves the curved surface of the cylinder?
a. 20%
b. 40%
c. 60%
d. 80%
26. If a 10 A current flows for two minutes, how much charge has
passed through this circuit?
a. 10 C
b. 12 C
c. 20 C
d. 1200 C
27. If the voltage on a capacitor is doubled, then the energy
stored by the capacitor
a. stays the same
b. doubles
c. quadruples
d. halves
28. A uniform spherical shell of charge of radius R surrounds a
point charge at its center. The point charge has value Q and
the shell has total charge -Q. The electric field at a
distance R/2 from the center
a. is zero
b. does not depend on the charge of the spherical shell
c. is half of what it would be if only the point charge were
present
d. is directed inward if Q>0.
29. A 1 pF capacitor is connected in parallel with a 2 pF
capacitor, the parallel combination then being connected in
series with a 3 pF capacitor. The resulting equivalent
capacitance is
a. 1.5 pF
b. 3 pF
c. 4.5 pF
d. 6 pF
30. If
R,
is
a.
b.
c.
d.
the current density in a wire is given by j = kr, 0 < r <
where R is the radius of the wire, the current in the wire
kR2
kR2/2
kR3/3
2ãkR3/3
31. In the circuit shown, the current in the 4-Ω resistor is 1.5
A. What is the current through the 5-Ω resistor?
a.
b.
c.
d.
1 A
1.5 A
3 A
6 A
32. If a point charge is located at the center of a cube and the
electric flux through one face of the cube is 5.0 Nm2/C, what
is the total flux leaving the cube?
a. 5.0 Nm2/C
b. 20 Nm2/C
c. 25 Nm2/C
d. 30 Nm2/C
33. The earth's northern magnetic pole acts like
a. the north pole of a magnet
b. the south pole of a magnet
c. it has positive charge
d. it has negative charge
34. A current I flows in a straight wire of length L at an angle
of 30˚ from the direction of a magnetic field B. The
magnitude of the force on this wire is
a. 0
b. BIL
c. 0.5 BIL
d. not given
35. A current is flowing in a wire in direction 3i + 4j where the
direction of the magnetic field is 5j + 12k. The force on the
wire is in the direction
a. 0.71(i + j)
b. 0.78i - 0.58j + 0.24k
c. 0.78i + 0.58j + 0.24k
36. An alpha particle is moving at a speed of 5 x 105 m/s in a
direction perpendicular to a uniform magnetic field of
strength 4 x 10-2 T. The charge on an alpha particle is
3.2 x 10-19 C and its mass is 6.6 x 10-27 kg. As the alpha
particle moves, its velocity
a. decreases
b. is still perpendicular to the magnetic field
c. gains a component in the direction of the magnetic field
d. gains a component opposite to the direction of the
magnetic field
37. An alpha particle is moving at a speed of 5 x 105 m/s in a
direction perpendicular to a uniform magnetic field of
strength 4 x 10-2 T. The charge on an alpha particle is
3.2 x 10-19 C and its mass is 6.6 x 10-27 kg. The magnitude
of the force on the alpha particle is
a. 0
b. 6.4 x 10-15 N
c. dependent upon the alpha particle's mass
d. answers b and c are correct
38. An alpha particle is moving at a speed of 5 x 105 m/s in a
direction perpendicular to a uniform magnetic field of
strength 4 x 10-2 T. The charge on an alpha particle is
3.2 x 10-19 C and its mass is 6.6 x 10-27 kg. The radius of
the path of the alpha particle is
a. changing
b. 0.26 m
c. 0.52 m
d. 3.9 m
39. An alpha particle is moving at a speed of 5 x 105 m/s in a
direction perpendicular to a uniform magnetic field of
strength 4 x 10-2 T. The charge on an alpha particle is
3.2 x 10-19 C and its mass is 6.6 x 10-27 kg. The time it
takes the alpha particle to complete one revolution around
its path is
a. 5.2 x 10-7 s
b. 1.0 x 10-6 s
c. 3.2 x 10-6 s
d. 6.5 x 10-6 s
40. A proton is moving at a speed of 3.2 x 106 m/s at an angle of
80° to a uniform magnetic field of strength 1.5 x 10-4 T.
What is the direction of the force on the proton?
a. perpendicular to the magnetic field
b. parallel to the magnetic field
c. at an angle of 80ø to the magnetic field
d. at an angle of 10ø to the magnetic field
41. A rectangular loop of wire of width 10 cm and length 20 cm
has a current of 2.5 A flowing through it. Two sides of the
loop are oriented parallel to a uniform magnetic field of
strength 0.037 T, the other two sides being perpendicular to
the magnetic field. The torque on the loop is
a. 0.025 m•N
b. 0.050 m•N
c. 0.0093 m•N
d. 0.019 m•N
42. A wire carries a current directly upwards in the wall of a
house. The direction of the magnetic field due to this
current at a point directly east of the wire is directed
a. north
b. south
c. east
d. in a direction that cannot be found with the information
given
43. Two parallel wires carry currents in the same direction. The
current in one wire is doubled, the other current remaining
constant. The force between the wires
a. remains the same
b. doubles
c. quadruples
d. rotates 90 degree
44. A superconducting wire has a mass of 0.15 g per meter of
length. If the earth's magnetic field is horizontal and of
magnitude 0.5 x 10-4 T, what current would the wire have to
carry if the magnetic force on the wire equals the
gravitational force.
a. 2.9 A
b. 29 A
c. 290 A
d. 2900 A
45. The coulomb is the same as
a. A•s
b. A/s
c. T•A/m
d. all of the above
46. In
a.
b.
c.
d.
using Ampere's law, the integral
must be evaluated around a circular path
must be evaluated around a closed path
must be evaluated around a path that lies in a plane
must be evaluated in a counter-clockwise direction
47. A circular loop of wire of radius 10 cm carries a current of
6A. The magnetic field at the center of the loop is
a. 3.8 x 10-7 T
b. 1.2 x 10-7 T
c. 1.2 x 10-5 T
d. 3.8 x 10-5 T
48. A semicircular wire of radius R connects two straight wire
segments. If a current I flows along the wire, the magnetic
field at the center of the semicircular wire due to the
current in the semicircular wire is
a. εoI/2R
b. εoI/4R
c. εoI/8R
d. εoI/4πR
49. The magnetic field at the center of a square loop of side L
is εoI/4πL times
a. 23/2
b. 27/2
c. 2-1/2
d. 2
50. Magnetic flux depends upon
a. the magnetic field
b. the area involved
c. the orientation of the area with respect to the field
d. all of the above
51. A ten loop coil of area 0.23 m2 is in a 0.047 T uniform
magnetic field oriented so that the maximum flux goes through
the coil. This flux is
a. 1.1 x 10-3 Tm2
b. 1.1 x 10-2 Tm2
c. 1.1 x 10-1 Tm2
d. 3.4 x 10-2 Tm2
52. A ten loop coil of area 0.23 m2 is in a 0.047 T uniform
magnetic field oriented so that the maximum flux goes through
the coil. The emf induced in the coil is
a. 0
b. 1.1 x 10-3 V
c. 1.1 x 10-2 V
d. 1.1 x 10-1 V
53. A circular loop of wire of area 25 cm2 lies in the plane of
the paper. An increasing magnetic field B is coming out of
the paper. What is the direction of the induced current in
the loop?
a. There is no current
b. clockwise
c. counterclockwise
d. counterclockwise then clockwise
54. A circular loop of wire of area 25 cm2 lies in the plane of
the paper. An decreasing magnetic field B is coming out of
the paper. What is the direction of the induced current in
the loop?
a. There is no current
b. clockwise
c. counterclockwise
d. counterclockwise then clockwise
55. A circular loop of wire is in the plane of the paper. The
north pole of a bar magnet is being moved toward the center
of the loop from a position in front of the paper. The
direction of the induced current in the loop is
a. north
b. south
c. clockwise
d. counterclockwise
56. A 200-loop coil of cross sectional area 8.5 cm2 lies in the
plane of the paper. Directed out of the plane of the paper is
a magnetic field of 0.06 T. The field out of the paper
decreases to 0.02 T in 12 milliseconds. What is the direction
of the current induced?
a. clockwise
b. counterclockwise
c. clockwise to counterclockwise
d. counterclockwise to clockwise
57. If the number of turns on the secondary coil of a transformer
are less than those on the primary, the result is a
a. step-down transformer
b. step-up transformer
c. a 120-V transformer
d. a dc transformer
58. A transformer changes the 10,000 V power line to 120 V. If
the primary coil contains 750 turns, how many turns are on
the secondary?
a. 3
b. 9
c. 2.1 x 104
d. 6.3 x 104
59. A conducting rod of length L is moving perpendicular to a
magnetic field B. As the speed doubles, the magnitude of the
motional emf
a. stays the same
b. doubles
c. quadruples
d. halves
60. A conducting rod of length L = 0.65 m and resistance 2.0 ohms
is moved with speed v = 15 m/s perpendicular to a magnetic
field B = 4.4 x 10-3 T. The magnitude of the electric field
in the rod is
a. 4.3 x 10-2 V/m
b. 6.6 x 10-2 V/m
c. 6.8 x 10-3 V/m
d. 6.1 x 10-5 V/m
ANSWERS
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
a
True
d
a
b
False
d
a
False
d
a
b
a
b
b
a
b
a
b
d
a
d
a
False
c
d
c
b
a
d
b
d
b
c
b
b
b
b
c
a
d
a
b
b
a
b
d
b
b
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
d
b
a
b
c
d
b
a
b
b
b
εo = 8.85 x 10-12 C2/Nm2
METRIC PREFIXES
Prefix: Symbol:
Magnitude:
Prefix: Symbol:
Magnitude:
Yotta-
Y
1024
deci-
d
10-1
Zetta-
Z
1021
centi-
c
10-2
Exa-
E
1018
milli-
m
10-3
Peta-
P
1015
micro-
μ
10-6
Tera-
T
1012
nano-
n
10-9
Giga-
G
109
pico-
p
10-12
Mega-
M
106
femto-
f
10-15
myria-
my
104
atto-
a
10-18
kilo-
k
103
zepto-
z
10-21
hecto-
h
102
yocto-
y
10-24
deka-
da
10