AZ L-31 Electrical Contractor Exam
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A|
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1. What is the primary purpose of an overcurrent protective device in
an electrical circuit?
a. To increase the voltage supplied to equipment
b. To protect conductors and equipment from excessive current
c. To improve the power factor of the circuit
d. To eliminate the need for grounding
Rationale: Overcurrent protective devices, such as fuses and circuit
breakers, interrupt current when it exceeds a specified level because
of an overload or short circuit. This helps prevent conductor
overheating, equipment damage, and electrical fires. They do not
replace grounding or eliminate all electrical hazards.
,2. Which formula expresses Ohm’s law?
a. Power equals voltage divided by resistance
b. Resistance equals current multiplied by power
c. Voltage equals current multiplied by resistance
d. Current equals resistance multiplied by voltage
Rationale: Ohm’s law is expressed as V = I × R, where V is voltage, I is
current, and R is resistance. It is used to calculate an unknown
electrical quantity when the other two are known. For example, a
current of 5 amperes flowing through a resistance of 10 ohms
produces a voltage drop of 50 volts.
3. A 120-volt circuit supplies a load drawing 10 amperes. What is the
power consumed by the load?
a. 12 watts
b. 120 watts
c. 1,200 watts
d. 12,000 watts
Rationale: Electrical power in a DC circuit or a purely resistive single-
phase AC circuit is calculated using P = V × I. Multiplying 120 volts by
,10 amperes gives 1,200 watts. For AC circuits with a power factor
below 1, real power must also account for the power factor.
4. What is the primary function of the equipment grounding conductor?
a. To carry normal operating current continuously
b. To increase the available circuit voltage
c. To serve as the neutral conductor for all loads
d. To provide a low-impedance fault-current path that helps
protective devices operate
Rationale: The equipment grounding conductor connects exposed,
normally non-current-carrying metal parts to the grounding and
bonding system. If a fault energizes an equipment enclosure, the
conductor provides a low-impedance path for fault current, helping
the overcurrent protective device open the circuit. It is not intended to
carry normal load current.
5. What is the purpose of the neutral conductor in a typical 120/240-
volt single-phase, three-wire system?
a. To provide the grounding electrode connection
b. To carry the imbalance of current from line-to-neutral loads
c. To interrupt short-circuit current mechanically
, d. To replace both ungrounded conductors
Rationale: In a 120/240-volt split-phase system, the neutral is the
grounded circuit conductor and provides the return path for line-to-
neutral loads. When the two 120-volt legs supply balanced loads, their
neutral currents can cancel. The neutral is distinct from the equipment
grounding conductor, which serves a safety function.
6. Which instrument is most appropriate for measuring current without
disconnecting a conductor from an energized circuit?
a. Megohmmeter
b. Continuity tester
c. Clamp ammeter
d. Phase-sequence indicator
Rationale: A clamp ammeter measures current by detecting the
magnetic field around a conductor. It allows current measurement
without opening the circuit, provided the instrument is used correctly
and is rated for the circuit. A conventional clamp around both
outgoing and returning conductors may show little or no reading
because their magnetic fields can cancel.
7. What does the term “ampacity” mean?
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A|
Instant Download Pdf
1. What is the primary purpose of an overcurrent protective device in
an electrical circuit?
a. To increase the voltage supplied to equipment
b. To protect conductors and equipment from excessive current
c. To improve the power factor of the circuit
d. To eliminate the need for grounding
Rationale: Overcurrent protective devices, such as fuses and circuit
breakers, interrupt current when it exceeds a specified level because
of an overload or short circuit. This helps prevent conductor
overheating, equipment damage, and electrical fires. They do not
replace grounding or eliminate all electrical hazards.
,2. Which formula expresses Ohm’s law?
a. Power equals voltage divided by resistance
b. Resistance equals current multiplied by power
c. Voltage equals current multiplied by resistance
d. Current equals resistance multiplied by voltage
Rationale: Ohm’s law is expressed as V = I × R, where V is voltage, I is
current, and R is resistance. It is used to calculate an unknown
electrical quantity when the other two are known. For example, a
current of 5 amperes flowing through a resistance of 10 ohms
produces a voltage drop of 50 volts.
3. A 120-volt circuit supplies a load drawing 10 amperes. What is the
power consumed by the load?
a. 12 watts
b. 120 watts
c. 1,200 watts
d. 12,000 watts
Rationale: Electrical power in a DC circuit or a purely resistive single-
phase AC circuit is calculated using P = V × I. Multiplying 120 volts by
,10 amperes gives 1,200 watts. For AC circuits with a power factor
below 1, real power must also account for the power factor.
4. What is the primary function of the equipment grounding conductor?
a. To carry normal operating current continuously
b. To increase the available circuit voltage
c. To serve as the neutral conductor for all loads
d. To provide a low-impedance fault-current path that helps
protective devices operate
Rationale: The equipment grounding conductor connects exposed,
normally non-current-carrying metal parts to the grounding and
bonding system. If a fault energizes an equipment enclosure, the
conductor provides a low-impedance path for fault current, helping
the overcurrent protective device open the circuit. It is not intended to
carry normal load current.
5. What is the purpose of the neutral conductor in a typical 120/240-
volt single-phase, three-wire system?
a. To provide the grounding electrode connection
b. To carry the imbalance of current from line-to-neutral loads
c. To interrupt short-circuit current mechanically
, d. To replace both ungrounded conductors
Rationale: In a 120/240-volt split-phase system, the neutral is the
grounded circuit conductor and provides the return path for line-to-
neutral loads. When the two 120-volt legs supply balanced loads, their
neutral currents can cancel. The neutral is distinct from the equipment
grounding conductor, which serves a safety function.
6. Which instrument is most appropriate for measuring current without
disconnecting a conductor from an energized circuit?
a. Megohmmeter
b. Continuity tester
c. Clamp ammeter
d. Phase-sequence indicator
Rationale: A clamp ammeter measures current by detecting the
magnetic field around a conductor. It allows current measurement
without opening the circuit, provided the instrument is used correctly
and is rated for the circuit. A conventional clamp around both
outgoing and returning conductors may show little or no reading
because their magnetic fields can cancel.
7. What does the term “ampacity” mean?
