Download Unit 8 Practice Test: Electricity

Unit 8 Practice Test: Electricity
Multiple Guess
Identify the letter of the choice that best completes the statement or answers the question.
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1. What happens when a rubber rod is rubbed with a piece of fur, giving it a negative charge?
a. Protons are removed from the rod.
c. The fur is also negatively charged.
b. Electrons are added to the rod.
d. The fur is left neutral.
2. A repelling force occurs between two charged objects when
a. charges are of unlike signs.
c. charges are of equal magnitude.
b. charges are of like signs.
d. charges are of unequal magnitude.
3. Electric charge is
a. found only in a conductor.
c. found only in insulators.
b. conserved.
d. not conserved.
4. If a positively charged glass rod is used to charge a metal bar by induction,
a. the charge on the bar will be equal in magnitude to the charge on the glass rod.
b. the charge on the bar must be negative.
c. the charge on the bar must be positive.
d. the charge on the bar will be greater in magnitude than the charge on the glass rod.
5. Which of the following transfers charge most easily?
a. nonconductors
c. semiconductors
b. conductors
d. insulators
6. Which sentence best characterizes electric conductors?
a. They have low mass density.
b. They have high tensile strength
c. They have electric charges that move freely.
d. They are poor heat conductors.
7. Which sentence best characterizes electric insulators?
a. Charges on their surface do not move.
c. Electric charges move freely in them.
b. They have high tensile strength
d. They are good heat conductors.
8. The process of charging a conductor by bringing it near another charged object and then grounding the
conductor is called
a. charging by contact.
c. charging by polarization
b. induction.
d. neutralization.
____
9. The figure above demonstrates charging by
a. grounding.
c. polarization.
b. induction.
d. contact.
____ 10. If two point charges are separated by 1.5 cm and have charge values of 2.0 µC and –4.0 µC, respectively,
what is the value of the mutual force between them? (kc = 8.99 × 109 N•m2/C2)
a. 320 N
c. 8.0 × 10–12
–8
b. 3.6 × 10 N
d. 3.1 × 10–3 N
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____ 11. Consider a thundercloud that has an electric charge of 40.0 C near the top of the cloud and –40.0 C near the
bottom of the cloud. These charges are separated by about 2.0 km. What is the electric force between these
two sets of charges? (kc = 8.99 × 109 N•m2/C2)
a. 3.6 × 104 N
c. 3.6 × 106 N
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d. 3.6 × 107 N
b. 3.6 × 10 N
____ 12. Which of the following is NOT true for BOTH gravitational and electric forces?
a. The inverse square distance law applies.
b. Forces are conservative.
c. Potential energy is a function of distance of separation.
d. Forces are either attractive or repulsive.
____ 13. Two point charges, initially 2 cm apart, are moved to a distance of 10 cm apart. By what factor do the
resulting electric and gravitational forces between them change?
a. 5
c.
b. 25
d.
____ 14. If the charge and mass are tripled for two identical charges maintained at a constant separation, the electric
and gravitational forces between them will be changed by what factor?
a. 9
c.
b.
d. 18
____ 15. Two point charges have a value of 30 µC each and are 4 cm apart. What is the electric field at the midpoint
between the two charges? (kc = 8.99 × 109 N•m2/C2)
a. 4.5 × 107 N/C
c. .5 × 107 N/C
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b. 2.3 × 10 N/C
d. 0 N/C
____ 16. Two point charges are 10.0 cm apart and have charges of 2.0 µC and –2.0 µC, respectively. What is the
electric field at the midpoint between the two charges?
a. 2.9 × 107 N/C
b. 1.4 × 107 N/C
c. 7.2 × 106 N/C
d. 0 N/C
____ 17. The relative distribution of charge density on the surface of a conducting solid depends upon which of the
following?
a. the shape of the conductor
b. the mass density of the conductor
c. the type of metal the conductor is made of
d. the strength of Earth’s gravitational field
____ 18. At what point is the electric field of an isolated, uniformly charged, hollow metallic sphere greatest?
a. at the center of the sphere
c. at infinity
b. at the sphere’s inner surface
d. at the sphere’s outer surface
____ 19. If a conductor is in electrostatic equilibrium,
a. the total charge on the conductor must be zero.
b. the electric field inside the conductor must be zero.
c. any charges on the conductor must be uniformly distributed.
d. the conductor is grounded.
____ 20. If a conductor is in electrostatic equilibrium, the electric field inside the conductor
a. is directed inward.
c. is at its maximum level.
b. is directed outward.
d. is zero.
____ 21. If an irregularly-shaped conductor is in electrostatic equilibrium, charge accumulates
a. where the radius of curvature is smallest. c. evenly throughout the conductor.
b. where the radius of curvature is largest.
d. in flat places.
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____ 22. Two positive point charges are initially separated by a distance of 2 cm. If their separation is increased to 6
cm, the resultant electrical potential energy is equal to what factor times the initial electrical potential energy?
a. 3
c.
b. 9
d.
____ 23. A proton (q = 1.60 × 10-19 C) moves 10.0 cm on a path parallel to the direction of a uniform electric field of
strength 3.0 N/C. What is the change in electrical potential energy?
c. –4.8 × 10–20 J
a. 4.8 × 10–20 J
b. 1.6 × 10–20 J
d. –1.6 × l0–20 J
____ 24. A uniform electric field with a magnitude of 5.0 × 102 N/C is directed parallel to the positive x-axis toward
the origin. What is the change in electrical energy of a proton (q = 1.60 × 10–19 C) as it moves from x = 5 m to
x = 2 m?
c. 2.0 × 1021 J
a. 8.0 × 10–17 J
–16
b. 2.0 × 10 J
d. 500 J
–19
____ 25. Two protons, each having a charge of 1.60 × 10 C, are 2.0 × 10–5 m apart. What is the electrical potential
energy between the two charges?
c. 3.2 × 10–16 J
a. 1.1 × 10–23 J
d. 1.6 × 10–14 J
b. 3.2 × 10–19 J
–19
____ 26. When an electron (e = –1.6 × 10 C) moves 0.10 m along the direction of an electric field with a strength of
3.0 N/C, what is the magnitude of the potential difference between the electron’s initial and final points?
a. 4.8 × 10–19 V
c. 0.03 V
b. 0.30 V
d. 3.0 × 101 V
____ 27. A uniform electric field with a magnitude of 500 N/C is directed parallel to the positive x-axis. If the potential
at x = 5 m is 2500 V, what is the potential at x = 2 m?
a. 1000 V
c. 4000 V
b. 2000 V
d. 4500 V
____ 28. What will be the electric potential at a distance of 0.15 m from a point charge of 6.0 µC?
(kc = 8.99 × 109 N•m2/C2)
a. 5.4 × 104 V
c. 2.4 × 106 V
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d. 1.2 × 107 V
b. 3.6 × 10 V
____ 29. Two point charges with values of 3.4 µC and 6.6 µC are separated by 0.10 m. What is the electric potential at
the point midway between the two point charges? (kc = 8.99 × 109 N•m2/C2)
a. 1.8 × 106 V
c. 0.9 × 106 V
b. –0.9 × 106 V
d. 3.6 × 106 V
____ 30. A point charge of 3.0 µC is at the origin of a coordinate system, and a second point charge of –6.0 µC is at x =
1.0 m. What is the electric potential at the point where x = 0.50 m? (kc = 8.99 × 109 N•m2/C2)
a. 1.62 × 105 V
c. –1.08 × 105 V
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b. 1.08 × 10 V
d. –5.4 × 104 V
____ 31. Charge build up between the plates of a capacitor stops when
a. there is no net charge on the plates.
b. unequal amounts of charge accumulate on the plate.
c. the potential difference between the plates is equal to the potential difference between the
terminals of the battery.
d. the charge on both plates is the same.
____ 32. A capacitor consists of two metal plates; ____ is stored on one plate and ____ is stored on the other.
a. negative charge; positive charge
c. potential difference; internal resistance
b. potential energy; kinetic energy
d. residual charge; induced charge
____ 33. Increasing the separation of the two charged parallel plates of a capacitor when they are disconnected from a
battery will produce what effect on the capacitor?
a. It will increase the charge.
c. It will increase the capacitance.
b. It will decrease the charge.
d. It will decrease the capacitance.
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____ 34. Increasing the potential difference across the two plates of a capacitor will produce what effect on the
capacitor?
a. It will increase the charge.
c. It will increase the capacitance.
b. It will decrease the charge.
d. It will decrease the capacitance.
____ 35. A 0.25 µF capacitor is connected to a 9.0 V battery. What is the charge on the capacitor?
c. 2.8 × 10–8 C
a. 1.2 × 10–12 C
–6
d. 3.6 × 10–7 C
b. 2.2 × 10 C
____ 36. What is the capacitance of a parallel-plate capacitor made of two square aluminum plates that are 4.0 cm in
length on each side and are separated by 5.0 mm? (ε0 = 8.85 × 10–12 C2/N•m2)
c. 2.8 × 10–12 F
a. 2.8 × 10–10 F
b. 1.0 × 10–6 F
d. 2.0 × 10–5 F
____ 37. A 0.50 µF capacitor is connected to a 12 V battery. How much electrical potential energy is stored in the
capacitor?
a. 2.0 × 10–12 J
c. 0.04 J
d. 3.6 × 10–5 J
b. 1.0 × 10–12 J
____ 38. How is current affected if the number of charge carriers decreases?
a. The current increases.
b. The current decreases.
c. The current initially decreases and then is gradually restored.
d. The current is not affected.
____ 39. How is current affected if the time interval decreases while the amount of charge remains the same?
a. The current increases.
b. The current decreases.
c. The current initially increases and then is gradually restored.
d. The current is not affected.
____ 40. The current in an electron beam in a cathode-ray tube is 7.0 × 10–5 A. How much charge hits the screen in 5.0
s?
a. 2.8 × 103 C
c. 3.5 × 10–4 C
b. 5.6 × 10–23 C
d. 5.3 × 10–4 C
____ 41. The amount of charge that moves through the filament of a light bulb in 2.00 s is 2.67 C. What is the current
in the light bulb?
a. 5.34 A
c. 0.835 A
b. 1.33 A
d. 0.417 A
____ 42. When electrons move through a metal conductor,
a. they move in a straight line through the conductor.
b. they move in zigzag patterns because of repeated collisions with the vibrating metal
atoms.
c. the temperature of the conductor decreases.
d. they move at the speed of light in a vacuum.
____ 43. What is the potential difference across a resistor of 5.0 Ω that carries a current of 5.0 A?
a. 1.0 × 102 V
c. 4.0 V
b. 25 V
d. 1.0 V
____ 44. Which of the following wires would have the GREATEST resistance?
a. an aluminum wire 10 cm in length and 3 cm in diameter
b. an aluminum wire 5 cm in length and 3 cm in diameter
c. an aluminum wire 10 cm in length and 5 cm in diameter
d. an aluminum wire 5 cm in length and 5 cm in diameter
____ 45. Which of the following wires would have the LEAST resistance?
a. an aluminum wire 20 cm in diameter at 40°C
b. an aluminum wire 20 cm in diameter at 60°C
c. an aluminum wire 40 cm in diameter at 40°C
d. an aluminum wire 40 cm in diameter at 60°C
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____ 46. What happens to the resistance of a superconductor when its temperature drops below the critical
temperature?
a. The resistance is equal to that of a semiconductor with the same dimensions.
b. The resistance doubles.
c. The resistance drops to zero.
d. The resistance reduces by one-half.
____ 47. When current is in a superconductor,
a. the current continues even if the applied potential difference is removed.
b. the current continues until the applied potential difference is removed.
c. the current quickly decays unless it is powered by an external energy source.
d. the superconductor MUST be above the critical temperature.
____ 48. If a 75 W light bulb operates at a voltage of 120 V, what is the current in the bulb?
a. 0.63 A
b. 1.6 A
c. 9.0 × 103 A
d. 1.1 × 10–4 A
____ 49. If a 5.00 × 102 W heater has a current of 4.00 A, what is the potential difference across the ends of the heating
element?
a. 2.00 × 103 V
c. 2.50 × 102 V
b. 125 V
d. 8.00 × 10–3 V
____ 50. If a lamp has a resistance of 120 Ω when it operates at a power of 1.00 × 102 W, what is the potential
difference across the lamp?
a. 110 V
c. 130 V
b. 120 V
d. 220 V
____ 51. An electric toaster requires 1100 W at 110 V. What is the resistance of the heating coil?
a. 7.5 Ω
c. 1.0 × 101 Ω
b. 9.0 Ω
d. 11 Ω
____ 52. If the potential difference across the bulb in a camping lantern is 9.0 V, what is the potential difference across
the battery used to power it?
a. 1.0 V
c. 9.0 V
b. 3.0 V
d. 18 V
____ 53. Three resistors with values of 4.0 Ω, 6.0 Ω, and 8.0 Ω, respectively, are connected in series. What is their
equivalent resistance?
a. 18
c. 6.0
b. 8.0
d. 1.8
____ 54. Three resistors with values of 4.0 Ω, 6.0 Ω, and 10.0 Ω are connected in parallel. What is their equivalent
resistance?
a. 20.0 Ω
c. 6.0 Ω
b. 7.3 Ω
d. 1.9 Ω
____ 55. What is the equivalent resistance for the resistors in the figure above?
a. 1.3 Ω
c. 3.0 Ω
b. 2.2 Ω
d. 7.5 Ω
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____ 56. What is the equivalent resistance for the resistors in the figure above?
a. 7.5 Ω
c. 16 Ω
1
b. 1.0 × 10 Ω
d. 18 Ω
____ 57. Two resistors with values of 6.0 Ω and 12 Ω are connected in parallel. This combination is connected in series
with a 2.0 Ω resistor and a 24 V battery. What is the current in the 2.0 Ω resistor?
a. 2.0 A
c. 6.0 A
b. 4.0 A
d. 12 A
Short Answer
58. How are gravitational and electric force alike?
59. How are gravitational and electric force different?
60. In the figure shown above, why do only half of the lines originating from the positive charge terminate on the
negative charge?
61. Draw the lines of force representing the electric field around a proton.
62. Draw the lines of force representing the electric field around an electron.
63. Is the charge shown in the figure above positive or negative?
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64. Is the charge shown in the figure above positive or negative?
65. Electrical potential energy is a result of what interaction?
66. What is potential difference?
67. How are electric potential and electrical potential energy related?
68. What is capacitance?
69. Draw a schematic diagram that contains three resistors and one battery.
70. Draw a schematic diagram that contains one battery, two resistors, one capacitor, and one closed switch.
71. In the schematic diagram above, will there be a current?
Problem
72. Three resistors with values of 18 Ω, 26 Ω, 9 Ω, respectively, are connected in series. What is their equivalent
resistance?
73. Three resistors with values of 28 Ω, 58 Ω, 22 Ω, respectively, are connected in series. What is their equivalent
resistance?
74. Three resistors with values of 16 Ω, 19 Ω, 25 Ω, respectively, are connected in parallel. What is their
equivalent resistance?
75. Three resistors with values of 11 Ω, 8 Ω, 2 Ω, respectively, are connected in parallel. What is their equivalent
resistance?
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Unit 8 Practice Test: Electricity
Answer Section
MULTIPLE GUESS
1.
B
20.
D
39.
A
2.
B
21.
A
40.
C
3.
B
22.
C
41.
B
4.
B
23.
C
42.
B
5.
B
24.
B
43.
B
6.
C
25.
A
44.
A
7.
A
26.
B
45.
A
8.
B
27.
C
46.
C
9.
C
28.
B
47.
A
10.
A
29.
C
48.
A
11.
C
30.
D
49.
B
12.
D
31.
C
50.
A
13.
D
32.
A
51.
D
14.
A
33.
D
52.
C
15.
D
34.
A
53.
A
16.
B
35.
B
54.
D
17.
A
36.
C
55.
B
18.
D
37.
D
56.
B
19.
B
38.
B
57.
B
SHORT ANSWER
58. Both are field forces, and both have inverse square laws.
59. Electric force is stronger than gravitational force. Also, electric force can be attractive or repulsive, but
gravitational force is always attractive.
60. Because the positive charge is twice as great as the negative charge.
61.
62.
63. negative
64. positive
65. The interaction between two charged objects
66. It is the change in the electrical potential energy associated with a charged particle divided by the charge of
the particle.
67. Electric potential is the electrical potential energy associated with a charged particle in an electric field
divided by the charge of the particle.
68. Capacitance is the measure of the ability of a device to store charge for a given potential difference.
69. okay
70.
PROBLEM
72. 53 Ω
71.
73.
108 Ω
74.
yes
6.4 Ω
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75.
1.4 Ω