• California CSLB
C10 Electrical 09/11/2026
Exam
California CSLB C10 Electrical Exam 3 review
test bank with over 400 questions and correct
detailed answers
Which of the following is an approved insulating material for lampholders of the screw-shell type?
A)Porcelain
B)Copper
C)Zinc
D)PVC (plastic) - Correct Answer :The Correct Answer Is A
NEC Section 410.72 requires lighting fixtures of the screw-shell type to be constructed of porcelain or other
suitable insulating material.
P 1
, • California CSLB
C10 Electrical 09/11/2026
Exam
Auxiliary lighting equipment, not installed as part of the lighting fixture, must be installed in what type of
enclosure?
A)Porcelain
B)Glass
C)Metal
D)PVC (plastic) - Correct Answer :The Correct Answer Is C
Auxiliary equipment, including reactors, capacitors, resistors, and similar equipment must be enclosed in an
accessible, permanently installed metal cabinet. NEC Section 410.77(A).
How must a branch circuit supplying a domestic water heater with a capacity of 120 gallons or less be sized?
A)100 percent of its nameplate rating.
B)110 percent of its nameplate rating.
C)125 percent of its nameplate rating.
D)150 percent of its nameplate rating. - Correct Answer :The Correct Answer Is C
NEC Section 422.13 requires all branch circuits feeding a fixed storage-type water heater having a capacity of 120
gallons or less to have a rating not less than 125 percent of the nameplate rating of the water heater.
If a 60 gallon water heater has a nameplate rating of 4500 watts and is fed by a 2-wire, 240-volt circuit, what is
the minimum size NM cable conductors that can be used?
A)No. 14 AWG
B)No. 12 AWG
C)No. 10 AWG
D)No. 8 AWG - Correct Answer :The Correct Answer Is C
4500/240 = 18.75 amperes x 1.25 = 23.43 amperes. Since No. 12 AWG NM cable is rated for a maximum load of 20
amperes, the next higher wire size (No. 10 AWG) must be used.
The quantity of electricity used by the consumer is measured by a device called _____.
A)an ohmmeter
P 2
, • California CSLB
C10 Electrical 09/11/2026
Exam
B)a power factor meter
C)a watt-hour meter
D)an ammeter - Correct Answer :he Correct Answer Is C
Electricity is sold by the kilowatt hour and the watt-hour meter is used to register the amount of electricity
consumed.
What is the name of a direct-indicating instrument for measuring resistance?
A)Voltmeter
B)Wattmeter
C)Ohmmeter
D)Ammeter - Correct Answer :he Correct Answer Is C
The essential parts of an ohmmeter are a source of voltage, a resistor, and a voltmeter. The voltage is normally
supplied by a conventional battery and is usually connected to a variable rheostat so that the battery voltage
can be adjusted to a constant pre-determined value. The resistor is connected in series with the voltmeter and
the lead terminals that are connected to the unknown resistance to be measured. When the reading is taken, no
computation is necessary. The instrument indicates resistance directly on a scale calibrated in ohms.
A measuring instrument consisting of an enclosure containing resistance coils with convenient plugs or switches
for placing coils of various resistance in and out of a balancing circuit is called a _____.
A)volt-ohm-ammeter
B)voltmeter
C)current transformer
D)Wheatstone bridge - Correct Answer :The Correct Answer Is D
The Wheatstone bridge is a convenient device for measuring the resistance of electrical circuits or components
by comparison with a standard resistance of known values.
An instrument used to show the difference in phase and frequency between the voltages of two alternators is
called _____.
A)a tachometer
P 3
, • California CSLB
C10 Electrical 09/11/2026
Exam
B)a synchroscope
C)a light meter
D)None of the above. - Correct Answer :The Correct Answer Is B
When two alternators are about to be connected in parallel, the voltages of the two must be approximately the
same; their voltages must be exactly in phase; and their frequencies must be approximately the same. If these
differences are too great, the alternators are likely to pull entirely out of phase, thus causing a complete
shutdown. The synchro scope indicates what adjustments are necessary to meet the above conditions.
An instrument used to indicate or record the speed of a machine in revolutions per minute (rpm) is called _____.
A)a frequency meter
B)a footcandle meter
C)a tachometer
D)a synchroscope - Correct Answer :The Correct Answer Is C
Several designs of tachometers are available: centrifugal, eddy current, surface speed, vibrating reed, and high-
intensity stroboscope or photo types. Some tachometers are connected to a machine by means of belts or
gears while others are hand held. All have various scales from 0 to 50,000 rpm.
Modern ac power systems must be closely regulated to a constant frequency within 1 percent. What is the name
of the very sensitive instrument used to measure these small variations?
A)Frequency meter
B)Footcandle meter
C)Tachometer
D)Synchroscope - Correct Answer :The Correct Answer Is A
Most frequency meters are either of the ratio-meter design or the vibrating-reed design similar to the vibrating-
reed tachometers. Either type may be used to measure the frequency of any ac electrical circuit.
Which of the following instruments are used to measure temperatures?
A)Resistance thermometer
B)Radiation pyrometer
P 4
C10 Electrical 09/11/2026
Exam
California CSLB C10 Electrical Exam 3 review
test bank with over 400 questions and correct
detailed answers
Which of the following is an approved insulating material for lampholders of the screw-shell type?
A)Porcelain
B)Copper
C)Zinc
D)PVC (plastic) - Correct Answer :The Correct Answer Is A
NEC Section 410.72 requires lighting fixtures of the screw-shell type to be constructed of porcelain or other
suitable insulating material.
P 1
, • California CSLB
C10 Electrical 09/11/2026
Exam
Auxiliary lighting equipment, not installed as part of the lighting fixture, must be installed in what type of
enclosure?
A)Porcelain
B)Glass
C)Metal
D)PVC (plastic) - Correct Answer :The Correct Answer Is C
Auxiliary equipment, including reactors, capacitors, resistors, and similar equipment must be enclosed in an
accessible, permanently installed metal cabinet. NEC Section 410.77(A).
How must a branch circuit supplying a domestic water heater with a capacity of 120 gallons or less be sized?
A)100 percent of its nameplate rating.
B)110 percent of its nameplate rating.
C)125 percent of its nameplate rating.
D)150 percent of its nameplate rating. - Correct Answer :The Correct Answer Is C
NEC Section 422.13 requires all branch circuits feeding a fixed storage-type water heater having a capacity of 120
gallons or less to have a rating not less than 125 percent of the nameplate rating of the water heater.
If a 60 gallon water heater has a nameplate rating of 4500 watts and is fed by a 2-wire, 240-volt circuit, what is
the minimum size NM cable conductors that can be used?
A)No. 14 AWG
B)No. 12 AWG
C)No. 10 AWG
D)No. 8 AWG - Correct Answer :The Correct Answer Is C
4500/240 = 18.75 amperes x 1.25 = 23.43 amperes. Since No. 12 AWG NM cable is rated for a maximum load of 20
amperes, the next higher wire size (No. 10 AWG) must be used.
The quantity of electricity used by the consumer is measured by a device called _____.
A)an ohmmeter
P 2
, • California CSLB
C10 Electrical 09/11/2026
Exam
B)a power factor meter
C)a watt-hour meter
D)an ammeter - Correct Answer :he Correct Answer Is C
Electricity is sold by the kilowatt hour and the watt-hour meter is used to register the amount of electricity
consumed.
What is the name of a direct-indicating instrument for measuring resistance?
A)Voltmeter
B)Wattmeter
C)Ohmmeter
D)Ammeter - Correct Answer :he Correct Answer Is C
The essential parts of an ohmmeter are a source of voltage, a resistor, and a voltmeter. The voltage is normally
supplied by a conventional battery and is usually connected to a variable rheostat so that the battery voltage
can be adjusted to a constant pre-determined value. The resistor is connected in series with the voltmeter and
the lead terminals that are connected to the unknown resistance to be measured. When the reading is taken, no
computation is necessary. The instrument indicates resistance directly on a scale calibrated in ohms.
A measuring instrument consisting of an enclosure containing resistance coils with convenient plugs or switches
for placing coils of various resistance in and out of a balancing circuit is called a _____.
A)volt-ohm-ammeter
B)voltmeter
C)current transformer
D)Wheatstone bridge - Correct Answer :The Correct Answer Is D
The Wheatstone bridge is a convenient device for measuring the resistance of electrical circuits or components
by comparison with a standard resistance of known values.
An instrument used to show the difference in phase and frequency between the voltages of two alternators is
called _____.
A)a tachometer
P 3
, • California CSLB
C10 Electrical 09/11/2026
Exam
B)a synchroscope
C)a light meter
D)None of the above. - Correct Answer :The Correct Answer Is B
When two alternators are about to be connected in parallel, the voltages of the two must be approximately the
same; their voltages must be exactly in phase; and their frequencies must be approximately the same. If these
differences are too great, the alternators are likely to pull entirely out of phase, thus causing a complete
shutdown. The synchro scope indicates what adjustments are necessary to meet the above conditions.
An instrument used to indicate or record the speed of a machine in revolutions per minute (rpm) is called _____.
A)a frequency meter
B)a footcandle meter
C)a tachometer
D)a synchroscope - Correct Answer :The Correct Answer Is C
Several designs of tachometers are available: centrifugal, eddy current, surface speed, vibrating reed, and high-
intensity stroboscope or photo types. Some tachometers are connected to a machine by means of belts or
gears while others are hand held. All have various scales from 0 to 50,000 rpm.
Modern ac power systems must be closely regulated to a constant frequency within 1 percent. What is the name
of the very sensitive instrument used to measure these small variations?
A)Frequency meter
B)Footcandle meter
C)Tachometer
D)Synchroscope - Correct Answer :The Correct Answer Is A
Most frequency meters are either of the ratio-meter design or the vibrating-reed design similar to the vibrating-
reed tachometers. Either type may be used to measure the frequency of any ac electrical circuit.
Which of the following instruments are used to measure temperatures?
A)Resistance thermometer
B)Radiation pyrometer
P 4
