Download Unit 7 Assessment

Physical Science Unit 7 Assessment: Waves and Electricity
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
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1. Sound waves
a. require a medium.
c. cannot travel through liquids.
b. are unrelated to vibrations.
d. can travel in a vacuum.
2. Light waves
a. require a medium.
c. cannot travel through liquids.
b. cannot travel through solids.
d. are electromagnetic waves.
3. Water waves
a. transport energy and water.
c. transport water but not energy.
b. transport energy but not water.
d. are not mechanical waves.
4. Sound waves are
a. transverse waves.
c. circular waves.
b. longitudinal waves.
d. polarized waves.
5. Light waves are
a. transverse waves.
c. rotating waves.
b. longitudinal waves.
d. circular waves.
6. A train of waves is moving at a speed of 30 m/s. The frequency of the waves is 10 Hz. What is the
wavelength?
a. 300 m
c. 3 m
b. 30 m
d. 0.1 m
7. A sound wave in air has a frequency of 680 cycles per second. What is the approximate wavelength of the
sound wave?
a. 680 m
c. 340 m
b. 0.5 m
d. 20 m
8. The frequency of a sound wave determines
a. the pitch of the sound.
c. how fast the sound travels.
b. how loud the sound is.
d. the magnitude of the compression.
9. How loud a sound is depends on
a. the wavelength of the sound.
c. the amplitude of the waves.
b. the pitch of the sound.
d. the medium.
10. The difference between visible light and X rays is that
a. the amplitude of visible light is greater.
c. they travel through a different medium.
b. the speed of X rays is greater.
d. the frequency of X rays is greater.
11. The color of light is determined by ____ of the light waves.
a. the medium
c. the frequency
b. the speed
d. the amplitude
12. Which type of electromagnetic wave has the greatest wavelength?
a. visible light
c. radio waves
b. microwaves
d. X rays
13. A wave with a frequency of 0.5 Hz and a speed of 10 m/s has a wavelength of
a. 50 m.
c. 20 m.
b. 0.5 m.
d. 0.2 m.
14. Which type of electromagnetic waves has slightly longer wavelengths than red light?
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a. yellow light
c. ultraviolet light
b. infrared light
d. green light
Which type of waves has wavelengths longer than microwaves?
a. infrared
c. radio waves
b. visible light
d. gamma rays
Which type of electromagnetic waves has the highest frequency?
a. gamma rays
c. infrared
b. ultraviolet light
d. microwaves
Which type of electromagnetic radiation is used to kill cancer cells?
a. microwaves
c. ultraviolet rays
b. gamma rays
d. sunlight
When light rays reflect off a rough surface, they
a. scatter in many different directions.
b. converge toward the normal.
c. diverge away from the normal.
d. decrease their speed and change their angle.
The law of reflection states that when light rays reflect off a surface the angle of incidence
a. is one-half the angle of reflection.
c. is twice the angle of reflection.
b. equals the angle of reflection.
d. equals the angle of refraction.
An orange looks orange because it
a. reflects orange light and absorbs other colors.
b. absorbs orange light and reflects other colors.
c. reflects red and yellow light only.
d. absorbs red and yellow light only.
The effect in which white light separates into different colors is called
a. magnification.
c. reflection.
b. refraction.
d. dispersion.
____ 22. Which drawing illustrates the law of reflection?
a. a
c. c
b. b
d. d
____ 23. There is a repulsive force between two charged objects when
a. their charges are of unlike sign.
b. they have the same number of protons.
c. their charges are of like sign.
d. they have the same number of electrons.
____ 24. There is an attractive force between two charged objects when
a. their charges are of unlike sign.
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b. they have the same number of protons.
c. their charges are of like sign.
d. they have the same number of electrons.
When a glass rod is rubbed with silk and becomes positively charged,
a. electrons are removed from the rod.
c. protons are removed from the silk.
b. protons are added to the silk.
d. the silk remains neutral.
When there is an equal amount of positive and negative charges on an object, the object is
a. positively charged.
c. neutral.
b. negatively charged.
d. supercharged.
Potential difference is measured in
a. amperes.
c. coulombs.
b. volts.
d. joules.
Batteries typically have
a. two positive terminals.
c. one positive and one negative terminal.
b. two negative terminals.
d. no terminals.
Current is the rate at which charges move through a(n)
a. conductor.
c. voltage.
b. insulator.
d. joule.
Potential differences cause
a. electrons to move from the positive terminal to the negative terminal.
b. electrons to move from the negative terminal to the positive terminal.
c. protons to move from the positive terminal to the negative terminal.
d. protons to move from the negative terminal to the positive terminal.
Resistance is caused by
a. internal friction.
c. proton charge.
b. electron charge.
d. a heat source.
The SI unit of resistance is the
a. volt.
c. ohm.
b. ampere.
d. joule.
Whether or not charges will move in a material depends partly on how tightly _____ are held in the atoms of
the material.
a. electrons
c. protons
b. neutrons
d. resistors
A flashlight bulb with a potential difference of 4.5 V across its filament has a power output of 8.0 W. How
much current is in the bulb filament?
a. 3.7 A
c. 0.23 A
b. 1.8 A
d. 0.56 A
What is the potential difference across a resistor that dissipates 5.00 W of power and has a current of 5.0 A?
a. 1.0 V
c. 4.00 V
b. 125 V
d. 0.20 V
There is a potential difference of 12 V across a resistor with 0.25 A of current in it. The resistance of the
resistor is
a. 48 
c. 12 
b. 24 
d. 0.021 
A 13  resistor has 0.050 A of current in it. What is the potential difference across the resistor?
a. 6.5 V
c. 0.065 V
b. 0.65 V
d. 0.0065 V
____ 38. A resistor has a resistance of 280 . How much current is in the resistor if there is a potential difference of
120 V across the resistor?
a. 160 A
c. 0.12 A
b. 0.43 A
d. 2.3 A
____ 39. A set of electric trains are powered by a 9V battery. What is the resistance of the trains if they draw 3.0 A of
current?
a. 3 
c. 27 
b. 0.03 
d. 2.7 
____ 40. The resistance of an insulator is
a. absent.
c. moderate.
b. very low.
d. high.
____ 41. Appliances connected so that they form a single pathway for charges to flow are connected in a(n)
a. series circuit.
c. open circuit.
b. parallel circuit.
d. closed circuit.
____ 42. If a lamp is measured to have a resistance of 45  when it operates at a power of 80.0 W, what is the current
in the lamp?
a. 2.10 A
c. 0.91 A
b. 1.3 A
d. 0.83 A
____ 43. An electric toaster has a power rating of 1100 W at 110 V. What is the resistance of the heating coil?
a. 7.5 
c. 10 
b. 9.0 
d. 11 
____ 44. If a 325 W heater has a current of 6.00 A, what is the resistance of the heating element?
a. 88.1 
c. 9.03 
b. 54.2 
d. 11.4 
____ 45. A device that protects a circuit from current overload is called a(n)
a. resistor.
c. circuit breaker.
b. capacitor.
d. closed circuit.
Short Answer
46. How does the electric force between two charged objects depend on distance?
47. What is electric current?
48. Why do electrical devices feel warm after they have been on for a period of time?
49. What is the difference between a conductor and an insulator?
50. Identify the types of elements in the schematic diagram above and the number of each type.
51. Is a current flowing in the schematic diagram above? Explain your answer.
52. Does the schematic diagram above represent a series or parallel circuit?
53. Does the schematic diagram above represent a series or parallel circuit?
54. What does a circuit breaker do?
Problem
55. There is a potential difference of 13 V across a resistor with 1.4 A of current in it. What is the resistance of
the resistor?
56. A 180  resistor has 0.10 A of current in it. What is the potential difference across the resistor?
57. A resistor has a resistance of 1.8 . How much current is in the resistor if there is a potential difference of 3.0
V across the resistor?
58. If a 75 W light bulb operates at a voltage of 120 V, what is the current in the bulb?
Essay
59. Explain the difference between mechanical waves and electromagnetic waves.
60. What is the electromagnetic spectrum and what types of waves are included in the spectrum?
61. Why does sound travel faster in solids than in liquids, and faster in liquids than in gases?
62. Compare and contrast refraction and reflection.
63. Describe two different forms of electromagnetic radiation and explain their use in technology.
64. What are some factors that would cause the resistance of two wires to be different? Which factors would
cause the resistance to increase and which factors would cause the resistance to decrease?
65. Compare and contrast series and parallel circuits.
Additional Questions
Add diagram of a transverse wave and include questions about it…label parts such as peak, trough, wavelength,
amplitude
Performance
Build a parallel circuit using the materials given.
Draw a parallel circuit and explain how you can tell if a string of holiday lights is wired in series or parallel.
Unit 7 Assessment
Answer Section
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SHORT ANSWER
46. ANS:
The electric force between two objects is inversely proportional to the square of the distance between the
objects. This means if the distance doubles, the force decreases by a factor of 4.
DIF: 2
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47. ANS:
It is the rate at which electric charges move through a conductor.
DIF: 1
REF: 2
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48. ANS:
Electrical devices feel warm because kinetic energy is transferred from moving electrons to surrounding
materials, causing the atoms to vibrate.
DIF: 1
REF: 2
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49. ANS:
A conductor has a low resistance because electrons can flow easily under the influence of an electric field. An
insulator has a high resistance because the charges inside the insulator do not move easily.
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50. ANS:
two resistors, one battery, one switch
OBJ: 5
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51. ANS:
No, because the switch is open, so there is not a closed-loop path for the electrons to follow.
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52. ANS:
parallel circuit
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53. ANS:
series circuit
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54. ANS:
A circuit breaker responds to current overload by opening a circuit.
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PROBLEM
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55. ANS:
9.3 
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18 V
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57. ANS:
1.7 A
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0.62 A
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ESSAY
59. ANS:
Mechanical waves require a medium in which to travel. Electromagnetic waves do not.
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60. ANS:
The electromagnetic spectrum refers to the full range of electromagnetic waves arranged from low frequency
to high frequency, or long wavelength to short wavelength. The types of electromagnetic waves, starting at
the low frequency end of the spectrum, are radio waves, microwaves, infrared light, visible light, ultraviolet
light, X rays, and gamma rays.
DIF: 2
REF: 2
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61. ANS:
When a particle of a medium is disturbed, it will cause a neighboring particle to be disturbed. The closer the
particles are and the more tightly they are bound, the faster the disturbance will travel through the medium.
The particles of solids are very close together, the particles of liquids are not as close, and the particles of a
gas are relatively far away from each other.
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62. ANS:
Both refraction and reflection occur when a wave traveling through a medium encounters a different medium.
Reflection involves the wave bouncing back into the original medium, while refraction involves the wave
changing direction as it passes into the new medium.
DIF: 2
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63. ANS:
Answers will vary. X rays, with high energy and short wavelengths, are used to produce images of the body’s
interior; visible light, which illuminates objects in the usual way; infrared, with wavelengths longer than red
light, can be used to keep food warm; microwaves, with still longer wavelengths, can be used for cooking and
for communication; radio waves, with the longest wavelengths, can be used in communication and radar.
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64. ANS:
Two wires can have different resistances because of length, cross-sectional area, temperature, and the kind of
material the wire is made of. The longer a wire is the greater the resistance, and the greater the cross-sectional
area the less the resistance.
DIF: 2
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65. ANS:
Both series and parallel circuits provide conducting paths for electricity. However, a series circuit provides a
single pathway. An interruption affects the movement of electrons throughout the entire circuit. Parallel
circuits provide two or more conducting pathways. An interruption does not necessarily affect the entire
circuit, as alternate paths are available for electron movement to continue.
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