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Electrical Practice
Multiple Choice
Identify the choice that best completes the statement or answers the question.
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1.
What is the term for an amount of charge equal to 6.25 x 1018 electrons?
a. ampere
b. volt
c. coulomb
d. watt
2.
In order to have current flow, a circuit must be
a. closed
b. open
c. shorted
d. grounded
3.
The neutral conductor is also referred to as the _____ conductor.
a. hot
b. grounded
c. grounding
d. safety
4.
The unit of electrical “pressure” that causes current to flow is called the
a. ampere
b. ohm
c. volt
d. watt
5.
The unit of resistance is the
a. ampere
b. ohm
c. volt
d. watt
6.
An opposition to current flow that occurs in alternating current circuits is called
a. current
b. resistance
c. impedance
d. voltage
7.
An electrical device is listed as 3,000 watts. Approximately how many horsepower is this?
a. 1/4
b. 1/6
c. 4
d. 6
8.
The statement “current is directly proportional to voltage and inversely proportional to resistance”
is know as _____ law.
a. Ampere’s
b. Coulomb’s
c. Ohm’s
d. Volt’s
9.
An electric motor is running on 120 V. The current is measured to be 2 A. How many ohms of
resistance is the motor?
a. 60
b. 118
c. 122
d. 240
10.
A toaster is listed as 1560 W. When it is plugged into a 120 V circuit and starts to make toast,
how many amperes will it draw?
a. 1440
b. 1680
c. 13
d. 187,200
11.
The three substances that form natural magnets are
a. iron, boron, and cobalt
b. copper, iron, and cobalt
c. copper, nickel, and boron
d. iron, nickel, and cobalt
12.
Magnetism can be explained in terms of _____ spin patterns.
a. electron
b. neutron
c. proton
d. quark
13.
Electrons in orbit around the nucleus of an atom have magnetic fields. Most of the electrons in
most materials pair up in such a way that their magnetic fields _____ leaving the materials nonmagnetic.
a. add
b. cancel
14.
A basic law of magnetism states that like poles _____ and opposite poles _____.
a. attract, repel
b. repel, attract
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15.
The strength of an electromagnet is primarily proportional to its
a. length
b. ampere-turns
c. diameter
d. core resistance
16.
The measure of a material’s willingness to be magnetized is called
a. permeability
b. reluctance
c. saturation
d. residual magnetism
17.
The measure of a material’s resistance to being magnetized is called
a. permeability
b. reluctance
c. saturation
d. residual magnetism
18.
The amount of magnetism left in a material after the magnetizing current has been removed is
a. permeability
b. reluctance
c. saturation
d. residual magnetism
19.
The strength of a magnetic field is an indication of how many flux lines per square inch there are.
This is called
a. residual magnetism
b. reluctance
c. permeability
d. flux density
20.
If an object is placed in the field of an AC electromagnet and slowly moved away, the object will
be
a. demagnetized
b. magnetized
21. When a conductor cuts magnetic lines of force, a voltage is induced into the conductor. This
principle is called
a. electromagnetic inductance
b. electric induction
c. magnetic inductance
d. electromagnetic induction
22. If a voltage is being induced into a conductor by electromagnetic induction, reversing the direction of
the magnetic field will
a. not change anything
b. reverse the polarity of the induced voltage
c. double the induced voltage
d. halve the induced voltage
23. If a voltage is being induced into a conductor by electromagnetic induction, reversing the direction of
motion of the conductor will
a. not change anything
b. reverse the polarity of the induced voltage
c. double the induced voltage
d. halve the induced voltage
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24. The direction of induced current can be determined by using the _____ left-hand generator rule.
a. Ohm
b. Kirchhoff
c. Fleming
d. Coulomb
25.
The magnetic quantity Weber (Wb) is equal to 100,000,000 lines of flux. If a conductor cuts
through 1 Weber per second (1 Wb / s), then a voltage of _____ volt(s) is induced into the conductor.
a. 100,000,000
b. 100,000
c. 100
d. 1
26. In electromagnetic induction, increasing the length of the conductor is normally done by
a. making the loop larger
b. adding more turns to the loop
c. rotating the loop faster
d. rotating the loop slower
27.
If a permanent magnet is first pushed into a coil of wire and then pulled out of the coil, the two
voltages induced (one for each direction of magnet movement) will be
a. the same polarity
b. different polarities
28.
When DC is applied to a coil, a plot of the current flow in the coil increasing from zero is a(n)
a. exponential curve
b. time constant curve
c. vertical line
d. horizontal line
29.
If a DC voltage is connected to an inductor, during the period of time called the first time
constant, the current will rise to about _____ % of its full value.
a. 50
b. 31.8
c. 100
d. 63.2
30.
The unit of inductance is the
a. farad (F)
b. henry (H)
c. ohm ( )
d. Weber (Wb)
31. In 1800 Alessandro Volta was experimenting with producing electricity. He called his battery a
a. cell
b. secondary cell
c. voltaic pile
d. D-cell
32. A battery is several _____ connected together.
a. cells
b. anodes
c. cathodes
d. electrodes
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33. A voltaic cell is constructed of two _____ metals and an electrolyte such as an acid, alkaline, or salt
solution.
a. like
b. unlike
c. salty
d. acidic
34. A cell which cannot be recharged is a _____ cell.
a. primary
b. secondary
35. The LeClanché cell is also known as a _____ cell.
a. alkaline
b. carbon-zinc
c. silver zinc
d. nickel-cadmium
36. An electrolyte can be checked to ensure that it has correct chemical composition by measuring its
a. relative gravity
b. specific gravity
c. relative resistance
d. specific resistance
37. As lead-acid batteries age, they may lose some of their capacity. To load test a battery, a load of
three times the ampere-hour rating is connected to the battery. The voltage is monitored and after _____
minutes, the voltage should be above _____ % of the rated voltage.
a. 5, 20
b. 3, 100
c. 5, 80
d. 3, 80
38. Nickel-cadmium (ni-cad) cells can produce large amounts of current (similar to lead-acid cells) and
can be recharged about _____ times.
a. 500
b. 1000
c. 2000
d. 5000
39. Thermocouples produce voltage because of the action of two unlike metals. The voltage produced
depends on the type of metals used and the _____ difference between the ends of the thermocouple
assembly.
a. distance
b. height
c. time
d. temperature
40. Piezoelectricity refers to electricity produced by some materials when they are subjected to
a. sunlight
b. pressure
c. heat
d. high temperatures
41. Several cells connected together are called a
a. primary cell
b. battery
c. secondary cell
d. voltage stack
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42.
A voltaic cell is constructed of two unlike metals and an electrolyte such as an _____, alkaline or
salt solution.
a. ion
b. saline
c. salty
d. acid
43. The amount of voltage produced by a cell depends on the materials used to make it. A list of metals
showing their willingness to accept electrons is called the _____ series of metals.
a. automotive
b. ionic
c. electromotive
d. electronic
44. A cell which can be recharged is a _____ cell.
a. primary
b. secondary
45. The current capacity of most cells and batteries is listed in base units of
a. volt-seconds
b. watt-hours
c. ampere-hours
d. volt-hours
46. The output voltage of a battery (or cell) measured with no load connected will be different than the
voltage with a load connected because the battery (cell) has internal
a. inductance
b. resistance
c. capacitance
d. reactance
47. The measurement of the specific gravity of an electrolyte is done with a device called a(n)
a. hygrometer
b. hydrometer
48. During the charging of lead-acid batteries, it is possible that _____ will be formed. Caution should
be observed because this is the most explosive element known.
a. hydrogen
b. oxygen
c. copper
d. lead
49. A ni-cad battery containing six cells has a terminal voltage of
a. 6.6 V
b. 13.2 V
c. 9 V
d. 7.2 V
50.
How many cells that are 0.5 V, 0.2 A each are required to create a 12 V battery that has a 0.5 A
capability?
a. 72
b. 48
c. 12
d. 24
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51.
A device used to change DC into AC is called a(n)
a. converter
b. alternator
c. oscillator
d. rectifier
52.
A wave in which the voltage rises at a constant rate with respect to time is a _____ wave.
a. cosine
b. linear
c. sine
d. pulsating
53.
Rotating machines (alternators) normally produce a wave shape which is called a _____ wave.
a. cosine
b. linear
c. sine
d. pulsating
54.
Alternating current waveforms repeat the same shape over and over. From the beginning of one
shape to the end of that shape is called a
a. cycle
b. hertz
c. frequency
d. rotation
55. The unit of frequency is the
a. cycle
b. hertz
c. frequency
d. rotation
56.
The amplitude of a waveform is measured from
a. peak-to-peak
b. either peak to zero
c. zero to the RMS level
d. zero to the effective level
57.
What is the RMS value of an AC voltage that has a 480 V peak?
a. 678.72 V
b. 305.76 V
c. 339.46 V
d. 753.53 V
58.
When AC voltage is rectified and converted into DC, the resulting waveform is normally not
pure, flat DC. The bumps that occur in the voltage are called
a. harmonics
b. cosines
c. ripples
d. peaks
59.
In an AC circuit, the voltage and current are frequently both sine waves. If they both pass
through zero heading in the same direction at the same time, they are said to be
a. in phase
b. out of phase
c. in leading phase
d. in lagging phase
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60.
The tendency for high frequency AC current to travel near the outer parts of conductors causes
the resistance of these conductors to be higher than on low frequency conductors. This is known as
a. insulation effect
b. phasing
c. skin effect
d. resistance
61.
The transformer winding which is the power input winding is called the _____ winding.
a. primary
b. secondary
c. tertiary
d. tapped
62.
The transformer winding which is the output winding is called the
a. primary
b. secondary
c. tertiary
d. tapped
63. A transformer has a 240 V primary and a 60 V secondary. With a 5 ohm load connected, what is the
primary current?
a. 12 A
b. 3 A
c. 0.75 A
d. 48 A
64.
A transformer supplying a house with 120 / 240 V has a secondary which is center tapped. The
conductor connected to the center is called the _____ conductor.
a. equipment ground
c. neutral
b. hot
d. ungrounded
65. A transformer metal toroid is assembled by
a. stacking small individual sheets of metal
b. winding a long continuous tape of metal into a spiral
c. casting a solid core and wrapping it with tape
d. bolting together two halves
66.
A transformer tape wound core is also called a _____ core.
a. toroid
b. solid
c. H
d. E
67.
Any transformer flux that does not follow the core and escapes into the surrounding air is called
a. magnetizing flux
b. flux coupling
c. flux leakage
d. flux reactance
68.
A transformer that does not isolate the out from the input is called a(n) _____ transformer.
a. distribution
b. step-up
c. auto
d. control
69.
I=
a. E / Z
b. Z * R
c. Z / R
d. none of these
70.
If the turn ratio is 4 to 1 then the amperage:
a. would be four times higher on the secondary side of the transformer.
b. would be four times higher on the primary side of the transformer.
c. would be four times lower on the secondary side of the transformer.
d. Both B and C
71.
In a three-phase motor, the speed of rotation of the magnetic field is called the _____ speed.
a. magnetic
b. slip
c. synchronous
d. rotor
72.
To reverse the direction of rotation of a three-phase motor, reverse
a. any one lead
b. any two leads
c. any three leads
d. all leads
73.
If a piece of machinery needs a replacement motor and will be damaged if the new motor rotates
the wrong way, the test equipment needed to test the rotation direction of the new motor is a
a. phase angle voltmeter
c. digital multimeter
b. MEGGER®
d. phase rotation meter
74.
Some motors are constructed so that they will operate on either of two voltages. When they are
connected to operate on the higher of the two voltages, the windings are connected in
a. series
b. parallel
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75. Some motors are constructed so that they will operate on either of two voltages. When they are
connected to operate on the lower of the two voltages, the windings are connected in
a. series
b. parallel
76. The squirrel-cage rotor is constructed of _____ and end _____ embedded in steel laminations.
a. bars, bars
b. rings, rings
c. bars, rings
d. rings, bars
77.
The torque of a squirrel-cage induction motor will be maximum when the phase angle between
the stator and rotor fields is
a. 0°
b. 90°
c. 180°
d. 270°
78.
When a squirrel-cage motor is first started, the value of the current draw is
a. equal to the running current
c. twice the running current
b. smaller than the running current
d. several times the running current
79.
An induction motor rotor rotates slower than the magnetic field. How much slower is normally
stated as slip speed in RPM or as percent slip? For most squirrel-cage induction motors the typical percent
slip is about _____ percent.
a. 0 to 1
b. 2 to 5
c. 5 to 10
d. 10 to 15
80.
When a normal induction motor is running, the rotor does not rotate as fast as the magnetic field
rotates. The rotor is being cut by the magnetic field which is inducing a voltage which is at the “rotor
frequency.” This frequency is _____ the synchronous frequency.
a. higher than
b. the same as
c. lower than
d. half of
81. A motor has a synchronous speed of 3600 RPM and an actual rotor speed of 3450 RPM. What is the
percent slip?
a. 4.17%
b. 4.35%
c. 24%
d. 23%
82. The squirrel-cage rotor code letters indicate the shape (type) of rotor bars. Different types of bars
have a large effect on the _____ of a motor.
a. operating voltage
c. starting torque
b. overload current
d. synchronous speed
83. If one phase of voltage to a three-phase motor opens, the motor may slow down, overheat, or possibly
stop. This condition is known as
a. double phasing
b. single phasing
c. triple phasing
d. free running
84.
In the consequent pole motor, when the polarity of half of the pole windings is reversed, thereby
effectively doubling the number of poles, the motor speed will
a. stay the same
b. cut in half
c. double
d. go to zero
85.
The wound-rotor induction motor is popular in industry because it has _____ starting torque and
_____ starting current.
a. low, low
b. low, high
c. high, low
d. high, high
86. The set of squirrel-cage bars on the rotor of a synchronous motor is used to start the motor and is
known as the
a. amortisseur winding
c. synchronous starter
b. starting bars
d. rotor bars
87.
a
a.
b.
88.
a.
89.
a.
A synchronous motor operated with no load and used for power factor correction is sometimes called
synchronizer
c. selsyn
capacitor
d. synchronous condenser
Selsyn motors operate on _____ phase voltage.
two
b. single
c. three
The differential selsyn has three stator windings connected in a wye and a rotor made of
three windings connected in a wye
b. one winding
____
90.
____
a. 1.9
b. 7.5
c. 4.5
d. 2.5
91.
What size disconnecting means is required for a single 5 HP, 115-volt motor on a separate branch
____
a. 30 amperes
b. 60 amperes
c. 100 amperes
d. none of these
92.
A 25 HP, induction type, Code letter D, 230-volt, three-phase motor has a nameplate current
____
a. 66.5 amperes
b. 83.13 amperes
c. 68 amperes
d. 85 amperes
93.
A 3 HP 120-volt motor with a nameplate FLA of 32.2 amperes requires a minimum branch-circuit
A motor control circuit transformer having a primary current of 1.5 amperes and installed within
the motor controller shall have primary overcurrent protection rated at not more than _____ amperes.
circuit?
rating of 66.5 amperes. The minimum branch-circuit ampacity permitted to supply this motor is?
rating of _____ amperes.
____
a. 40.25
b. 42.5
c. 39.1
d. 35.42
94.
What is the HP rating of a single-phase 200-volt motor with a current rating of 11.5 amperes?
a. 1.5 HP
b. 3 HP
c. 5 HP
d. 7.5 HP
95.
What is the minimum ampacity permitted for the feeder to supply the following group of 230-volt,
____
a. 143 amperes
b. 130 amperes
c. 163 amperes
d. 195 amperes
96.
If two motors are supplied by the same branch-circuit, the ampacity of the circuit conductors must
____
a. 25
b. 125
c. 110
d. 15
97.
A 3/4-HP, 240-volt, single-phase, no code letter motor is to be protected with an inverse-time
____
single-phase, squirrel-cage induction motors: one 10 HP, one 7.5 HP, one 5 HP, and one 2 HP?
be equal to the sum of the full-load current ratings of both motors plus _____ percent of the largest motor.
circuit breaker. The branch-circuit conductors are No. 14 AWG copper as permitted by Section 430.22(A).
What is the maximum size circuit breaker permitted to protect this motor?
a. 15 amperes
b. 20 amperes
c. 25 amperes
d. 30 amperes
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98.
____
a. 120 / 240 volts
c. 480 / 277 volts
b. 240 volts
d. 480 volts
99.
What is the minimum size THWN copper conductor permitted to feed a 200-volt, three-phase, 30
____
a. #3
b. #2
c. #1
d. 1/0
100.
The motor overload unit for a single-phase motor fed from an ungrounded 2-wire, single-phase
A horsepower rated motor controller is to be installed on a 480-volt delta connected,
corner-grounded, three-phase circuit. Which of the following voltage ratings would be approved for this
use?
HP, squirrel-cage induction motor? All terminations and devices are listed for 75 degree C terminations.
AC source will be placed in the ____________ conductor.
a.
neutral
b.
phase
c.
either one
d.
neither one