Mechanical Engineering Unit 31 To 40 Exam Namemultiple Choice Choose The One Alternative That Best Completes The Statement

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subject Pages 14
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subject Textbook Fundamentals of HVACR 3rd Edition
subject Authors Carter Stanfield, David Skaves
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page-pf1
Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the
question.
1)
1)
Ohm's law is a mathematical formula that describes the relationship between:
A)
Volts, amps, and ohms.
B)
Ohms, watts, and volts.
C)
Watts, volts, and amps.
D)
Volts, amps, ohms, and watts.
Answer:
A
A)
B)
C)
D)
2)
2)
Static electricity is:
A)
A standing electric charge created by displacing electrons.
B)
A standing electric charge created by displacing neutrons.
C)
Created by splitting atoms and releasing all the electrons in the atom.
D)
A standing electric charge created by displacing protons.
Answer:
A
A)
B)
C)
D)
3)
3)
Why are the spark plug wires on your car very thick on the outside?
A)
The wire must carry high current.
B)
Thicker insulation is used to carry high current.
C)
The insulation must hold back thousands of volts.
D)
Heavier wire is used to carry the high voltage.
Answer:
C
A)
B)
C)
D)
1
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4)
4)
In refrigeration and air conditioning, safety controls are wired:
A)
In parallel with the load they protect.
B)
In parallel with the power supply.
C)
In series with the load they protect.
D)
In either series or parallel with the load they protect.
Answer:
C
A)
B)
C)
D)
5)
5)
A substance that offers very little resistance to current flow is known as a(n):
A)
B)
C)
D)
Answer:
B
A)
B)
C)
D)
6)
6)
The three types of path arrangements for circuits are:
A)
Micro-voltage, low-voltage, high-voltage.
B)
Series, parallel, series-parallel.
C)
Open, shorted, grounded.
D)
Conductor, insulator, semiconductor.
Answer:
B
A)
B)
C)
D)
7)
7)
The voltage in a series circuit:
A)
Is inversely proportional to the load resistance.
B)
Is directly proportional to each load's current draw.
C)
Stays the same throughout the circuit.
D)
Drops across each load.
Answer:
D
A)
B)
C)
D)
2
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8)
8)
If an electric heater is rated at 15,000 W, and the voltage used is 240 V, what size breaker in amps
would be required?
A)
B)
C)
D)
Answer:
D
A)
B)
C)
D)
9)
9)
One hertz (Hz) is equivalent to:
A)
One cycle per minute.
B)
One thousand cycles per second.
C)
One thousand cycles per minute.
D)
One cycle per second.
Answer:
D
A)
B)
C)
D)
10)
10)
What makes a material a good electrical conductor?
A)
A large number of free electrons
B)
Having a large number of free protons
C)
Having eight electrons in the outer shell
D)
Having very few electrons
Answer:
A
A)
B)
C)
D)
11)
11)
What are the most common loads in HVACR systems?
A)
Lights
B)
Motors
C)
Resistance heaters
D)
Wires
Answer:
B
A)
B)
C)
D)
3
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12)
12)
In a parallel circuit:
A)
The current stays the same throughout the circuit.
B)
The voltage stays the same throughout the circuit.
C)
The heat stays the same throughout the circuit.
D)
The wattage stays the same throughout the circuit.
Answer:
B
A)
B)
C)
D)
13)
13)
Electrical power is measured in:
A)
B)
C)
D)
Answer:
D
A)
B)
C)
D)
14)
14)
In a basic electric circuit with a steady potential, when resistance decreases:
A)
Current decreases.
B)
Current remains the same.
C)
Current increases.
D)
The resistance has no effect on the current in an electric circuit.
Answer:
C
A)
B)
C)
D)
15)
15)
An electrical circuit is composed of a power source, a path for current to flow, and:
A)
A means of regulating power.
B)
Switch.
C)
Load.
D)
Element.
Answer:
C
A)
B)
C)
D)
4
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16)
16)
The electromotive force that causes electrons to move along a conductor is called:
A)
B)
C)
D)
Answer:
D
A)
B)
C)
D)
17)
17)
In a series circuit, total resistance is determined by:
A)
Adding the sum of all individual resistances.
B)
Dividing voltage into the current.
C)
Dividing resistance into amperage.
D)
Total resistance cannot be determined in a series circuit.
Answer:
A
A)
B)
C)
D)
18)
18)
The total resistance of a series circuit with resistances of 18 and 9 is:
A)
18 × 9 = 162
B)
(18 × 9)/(18 + 9) = 6
C)
18 — 9 = 9
D)
18 + 9 = 27
Answer:
D
A)
B)
C)
D)
19)
19)
What is the total circuit resistance of three heat strips wired in series if each strip has a resistance
of 12 ?
A)
B)
C)
D)
Answer:
C
A)
B)
C)
D)
5
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20)
20)
Electrical potential is measured in:
A)
B)
C)
D)
Answer:
A
A)
B)
C)
D)
21)
21)
Calculate the electric power for a 12-V DC circuit drawing 3 A?
A)
3 A × 12 V = 36 W
B)
12 V + 3 A = 15 W
C)
12 V/3 A = 4 W
D)
3 A/12 V = 0.25 W
Answer:
A
A)
B)
C)
D)
22)
22)
Electric current that flows in only one direction is called:
A)
Direct current.
B)
Potential current.
C)
Ellipsoidal current.
D)
Alternating current.
Answer:
A
A)
B)
C)
D)
23)
23)
Alternating current is typically available in:
A)
Single-phase, two-phase, and three-phase.
B)
Single-phase and three-phase.
C)
Unphased, positive-phased, and negative-phased.
D)
Single-phase and two-phase.
Answer:
B
A)
B)
C)
D)
6
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24)
24)
In an electrical circuit, watts are:
A)
One coulomb of electrons flowing in one second.
B)
Opposition to the flow of electricity.
C)
The ability to make current flow.
D)
The ability of electricity to do work.
Answer:
D
A)
B)
C)
D)
25)
25)
What is an electrical load?
A)
The power coming into a unit, usually labeled L1 and L2
B)
Any device in an electrical circuit
C)
A problem in a circuit that makes the electricity work harder, reducing efficiency
D)
An electrical device that requires power to operate
Answer:
D
A)
B)
C)
D)
26)
26)
Electrical resistance is measured in:
A)
B)
C)
D)
Answer:
C
A)
B)
C)
D)
27)
27)
The total circuit resistance of a parallel circuit will always be:
A)
The sum of all the individual resistances.
B)
The same as the highest individual resistance.
C)
More than the highest individual resistance.
D)
Less than the lowest individual resistance.
Answer:
D
A)
B)
C)
D)
7
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28)
28)
Electrical current is measured in:
A)
B)
C)
D)
Answer:
B
A)
B)
C)
D)
29)
29)
Good electrical insulators include:
A)
Ceramic, rubber, and plastic.
B)
Steel, iron, and aluminum.
C)
Gold, silver, and copper.
D)
Copper, aluminum, and steel.
Answer:
A
A)
B)
C)
D)
30)
30)
Before handling printed circuit boards, technicians should discharge any static electricity from
their bodies by:
A)
Momentarily grabbing both ends of the power source to neutralize themselves.
B)
Rubbing their feet several times on the carpet to remove excess electrons.
C)
Wiping their hands with a silk rag to remove excess electrons from their hands.
D)
Touching a grounded metal frame.
Answer:
D
A)
B)
C)
D)
31)
31)
The number of cyclic wave forms present at one time in an AC circuit is called:
A)
B)
C)
D)
Answer:
C
A)
B)
C)
D)
8
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32)
32)
Using Ohm's law, what is the amp draw of a circuit with a voltage of 240 V and a resistance of 10
?
A)
B)
C)
D)
Answer:
C
A)
B)
C)
D)
33)
33)
What material are most of the wires in your house made of?
A)
B)
C)
D)
Answer:
D
A)
B)
C)
D)
34)
34)
An electric circuit that contains a source and path without a load is called:
A)
A short circuit.
B)
An open circuit.
C)
A grounded circuit.
D)
A fundamental circuit.
Answer:
A
A)
B)
C)
D)
35)
35)
The current in a parallel circuit:
A)
Stays the same throughout the circuit.
B)
Drops across each load.
C)
Increases as more loads are added.
D)
Is directly proportional to each load's current draw.
Answer:
C
A)
B)
C)
D)
9
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36)
36)
In an electrical circuit,resistance is:
A)
One coulomb of electrons flowing in one second.
B)
Opposition to the flow of electricity.
C)
The ability to make current flow.
D)
The ability of electricity to do work.
Answer:
B
A)
B)
C)
D)
37)
37)
Electricity that is in motion with a current flow is referred to as:
A)
Hyperbolic electricity.
B)
Static electricity.
C)
Potential energy.
D)
Dynamic electricity.
Answer:
D
A)
B)
C)
D)
38)
38)
What is the current draw of a 1,200-W electric heater operating on a 120-V AC power supply?
A)
1,200 W/120 V = 10 A
B)
120 V/1,200 W = 0.1 A
C)
120 V + 1,200 W = 1,320 A
D)
1,200 W × 120 V = 144,000 A
Answer:
A
A)
B)
C)
D)
39)
39)
Electrons are:
A)
Positively charged particles located in the outer part of the atom.
B)
Negatively charged particles located in the center of the atom.
C)
Positively charged particles located in the center of the atom.
D)
Negatively charged particles located in the outer part of the atom.
Answer:
D
A)
B)
C)
D)
10
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40)
40)
Impedance is the combined effect of:
A)
DC resistance and AC resistance.
B)
Wattage and amperage.
C)
Potential and current.
D)
Resistance, inductive reactance, and capacitive reactance.
Answer:
D
A)
B)
C)
D)
41)
41)
What specification on the unit data plate should be used to size the power wire?
A)
The maximum overcurrent protection (MOCP)
B)
The locked rotor amps (LRA)
C)
The minimum circuit ampacity (MCA)
D)
The rated load amps (RLA)
Answer:
C
A)
B)
C)
D)
42)
42)
Battery-powered devices operate on:
A)
Modulating current (MC).
B)
Natural current (NC).
C)
Alternating current (AC).
D)
Direct current (DC).
Answer:
D
A)
B)
C)
D)
43)
43)
AC generators work by:
A)
A chemical reaction.
B)
Turning a coil of wire through a magnetic field.
C)
By spinning a loop of wire at high rates of speed until the electrons start to move.
D)
Rubbing two statically charged materials together.
Answer:
B
A)
B)
C)
D)
11
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44)
44)
All AC equipment is designed to operate at voltages within what percent of its rated power?
A)
B)
C)
D)
Answer:
B
A)
B)
C)
D)
45)
45)
In an AC resistive circuit:
A)
Voltage leads current.
B)
Current lags voltage.
C)
The voltage and current are in phase.
D)
Current leads voltage.
Answer:
C
A)
B)
C)
D)
46)
46)
How does a capacitor work?
A)
It stores electrons momentarily on its plates.
B)
It concentrates voltage like a funnel for electrons.
C)
It produces electrons through chemical means like a battery.
D)
It boosts voltage like a transformer.
Answer:
A
A)
B)
C)
D)
47)
47)
What unit specification should be used to size the overcurrent protection?
A)
The rated load amps (RLA)
B)
The maximum overcurrent protection (MOCP)
C)
The locked rotor amps (LRA)
D)
The minimum circuit ampacity (MCA)
Answer:
B
A)
B)
C)
D)
12
page-pfd
48)
48)
One problem resulting from operating an air conditioner using undersized power wiring is:
A)
The voltage at the unit will be too high.
B)
The amp draw will be too low.
C)
The wire will jump when the unit starts.
D)
The wire will get hot.
Answer:
D
A)
B)
C)
D)
49)
49)
Why can't impedances in series in an AC circuit simply be added to find the total circuit
impedance?
A)
Because the total impedance is always lower than the lowest single impedance in a series
circuit
B)
Because some of the impedance is lost through each load
C)
Because the currents through inductive, capacitive, and resistance loads in an AC circuit are
out of phase with each other.
D)
Because the impedance stays the same throughout a series circuit
Answer:
C
A)
B)
C)
D)
50)
50)
A transformer uses this electrical principle to increase or reduce voltage with no moving parts or
contacts.
A)
Resistance
B)
Electromotive force
C)
Induction
D)
Capacitance
Answer:
C
A)
B)
C)
D)
51)
51)
The voltage between any leg of a 480 V wye transformer and ground is:
A)
B)
C)
D)
Answer:
B
A)
B)
C)
D)
13
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52)
52)
What type of fuses should be used with air-conditioning systems?
A)
Rapid blow fuses
B)
Copper tubing cut to the size of a fuse
C)
One-time fuses
D)
Slow blow fuses
Answer:
D
A)
B)
C)
D)
53)
53)
Single-phase AC power is used:
A)
Only in residences.
B)
Only in Europe.
C)
Only in commercial buildings.
D)
In both residential and commercial buildings.
Answer:
D
A)
B)
C)
D)
54)
54)
How is the minimum circuit ampacity (MCA) calculated for an air-conditioning unit with more
than one motor?
A)
The amp draws of all the motors are added up.
B)
The largest motor amp draw is multiplied by 1.25 and the other motor amp draws are
added to it.
C)
The amp draw of each motor is multiplied by 1.25 and then summed.
D)
The amp draws of all the motors are added and multiplied by 1.25.
Answer:
B
A)
B)
C)
D)
55)
55)
What is the frequency of alternating current?
A)
The number of cyclic deviations that occur
B)
The number of complete cycles in a second
C)
The amount of current flowing
D)
How often alternating current is used
Answer:
B
A)
B)
C)
D)
14
page-pff
56)
56)
Why is AC instead of DC power transmitted to buildings?
A)
Since AC power goes both ways, it can redistribute power that is not used.
B)
Normal household lights will not work on DC power.
C)
DC power would require giant batteries.
D)
It is easier to step the voltage up and down with AC power.
Answer:
D
A)
B)
C)
D)
57)
57)
A delta three-phase power supply provides:
A)
120 V between the legs.
B)
240 V between the legs.
C)
208 V between the legs.
D)
480 V between the legs.
Answer:
B
A)
B)
C)
D)
58)
58)
The main operating principle of transformers is:
A)
Transductive current amplification.
B)
Magnetic transformation.
C)
Magnetic induction.
D)
Transductive voltage amplification.
Answer:
C
A)
B)
C)
D)
59)
59)
What is the purpose of a capacitor in an AC motor circuit?
A)
It boosts voltage like a transformer.
B)
It provides circuit overload protection.
C)
It provides a phase shift so the motor can start more easily.
D)
It holds a one-time charge to help the motor start.
Answer:
C
A)
B)
C)
D)
15
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60)
60)
What is the normal frequency of AC power in the United States?
A)
50 cycles per second
B)
60 cycles per second
C)
90 cycles per second
D)
25 cycles per second
Answer:
B
A)
B)
C)
D)
61)
61)
What is the impedance of a single-phase inductive circuit having a voltage of 240 V and a current
flow of 10 A?
A)
240 V/10 A = 24
impedance
B)
10 A/240 V = 0.042
impedance
C)
240 V × 10 A = 2,400
impedance
D)
Impedance cannot be calculated using only volts and amps.
Answer:
A
A)
B)
C)
D)
62)
62)
AC power can be converted to DC power through use of components called:
A)
B)
C)
D)
Answer:
C
A)
B)
C)
D)
63)
63)
How is the minimum circuit ampacity for an air-conditioning condensing unit calculated?
A)
(Compressor amps × 1.25) + fan amps
B)
Compressor amps + fan amps
C)
(Compressor amps + fan amps) × 1.25
D)
By the compressor locked rotor amps (LRA)
Answer:
A
A)
B)
C)
D)
16
page-pf11
64)
64)
If a conductor is coiled as in a relay coil, then passing current through it will ________ the
magnetic field.
A)
not change
B)
decrease
C)
Coils should not be coiled.
D)
intensify
Answer:
D
A)
B)
C)
D)
65)
65)
Most HVACR systems operate on:
A)
Natural current (NC).
B)
Modulating current (MC).
C)
Direct current (DC).
D)
Alternating current (AC).
Answer:
D
A)
B)
C)
D)
66)
66)
The frequency of AC power is measured in:
A)
B)
C)
D)
Answer:
D
A)
B)
C)
D)
67)
67)
Describe the construction of a capacitor.
A)
An anode and a cathode in an electrolyte
B)
A can full of electronic fluid with two wires
C)
A layer of positively charged semiconductor followed by a layer of negatively charged
semiconductor
D)
A layer of insulation between two layers of metal
Answer:
D
A)
B)
C)
D)
17
page-pf12
68)
68)
The formula for impedance is:
A)
B)
C)
D)
Answer:
D
A)
B)
C)
D)
69)
69)
In an AC capacitive circuit:
A)
Voltage leads current.
B)
The voltage and current are in phase.
C)
Current lags voltage.
D)
Current leads voltage.
Answer:
D
A)
B)
C)
D)
70)
70)
Alternating current frequency is measured in:
A)
B)
C)
D)
Answer:
B
A)
B)
C)
D)
71)
71)
How can the magnetism produced by a flowing electrical current be intensified enough to
produce useful work?
A)
Pass the magnetic field through a magnetic force field amplifier.
B)
Use a conductor with a current gap to create higher current levels.
C)
Reduce the amount of current traveling through the wire.
D)
Coil the conductor around a core of soft iron or steel.
Answer:
D
A)
B)
C)
D)
18
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72)
72)
Calculate the minimum circuit ampacity (MCA) for a rooftop unit that has the following data
listed on its name plate: compressor FLA 20, two fans FLA 2.5 each.
A)
MCA = 1.25 × (20 + 2.5 + 2.5) = 31.25 A
B)
MCA = 20 + 2.5 + 2.5 = 25 A
C)
MCA = 2 × (20 + 2.5 + 2.5) = 50 A
D)
MCA = (1.25 × 20) + 2.5 + 2.5 = 30 A
Answer:
D
A)
B)
C)
D)
73)
73)
The voltage between the "stinger" leg of a delta transformer and ground is:
A)
B)
C)
D)
Answer:
D
A)
B)
C)
D)
74)
74)
What does a transformer do?
A)
Increases or decreases incoming voltage
B)
Transforms DC current to AC current
C)
Transforms AC current to DC current
D)
Changes an electrical signal into a mechanical action
Answer:
A
A)
B)
C)
D)
75)
75)
Before attempting to use an electric meter to measure the circuits on a system, the technician
should:
A)
Disconnect the equipment ground wire to prevent a dangerous ground-loop circuit.
B)
Grab a grounded surface with your free hand to give any stray electricity a good path.
C)
Start with an inexpensive set of leads in case they burn up.
D)
Understand how the unit and the meter work.
Answer:
D
A)
B)
C)
D)
19
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76)
76)
Besides the normal electrical functions found on general-purpose multimeters, what additional
functions are common on multifunction meters intended for HVACR use?
A)
Volts and amps
B)
Watts and voltamps
C)
Volts and ohms
D)
Temperature, microfarads, and frequency
Answer:
D
A)
B)
C)
D)
77)
77)
What could happen to an analog meter if a voltage is tested that exceeds the setting on the meter?
A)
The meter can be damaged.
B)
The meter will protect itself by not reading the voltage, and no reading will be displayed.
C)
A coded series of beeps will indicate to the technician that the reading exceeds the meter
setting.
D)
The meter will display "OL" to indicate the reading is out of range.
Answer:
A
A)
B)
C)
D)
78)
78)
Capacitance meters measure the capacitance in a circuit or in a start capacitor. This is measured in
what unit?
A)
B)
C)
D)
Answer:
A
A)
B)
C)
D)
79)
79)
How are clamp-on ammeters used?
A)
They are clamped around both power wires feeding the circuit.
B)
They are clamped around one of the power wires feeding the circuit.
C)
They are clamped onto the load.
D)
They are clamped to the case of the unit.
Answer:
B
A)
B)
C)
D)
20

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