Arizona AZ L-77 Industrial
Electrical Contractor Practice
Exam | Questions, Verified
Answers & Detailed Rationales |
Complete Contractor License
Exam Prep Study Guide |
Updated 2026
1. What is the primary purpose of an equipment
grounding conductor?
A. To carry normal operating current
B. To increase circuit voltage
C. To provide a low-impedance path for fault current
D. To reduce conductor resistance
Correct answer: To provide a low-impedance path for
fault current
Rationale: The equipment grounding conductor provides
a low-impedance path for fault current so that the
overcurrent protective device can operate quickly and
disconnect the faulted circuit.
2. In a balanced three-phase system, what is the phase
relationship between the three phase voltages?
A. 60 degrees
B. 90 degrees
C. 120 degrees
D. 180 degrees
Correct answer: 120 degrees
,Rationale: The three phase voltages in a balanced three-
phase system are separated by 120 electrical degrees.
3. Which instrument is normally used to measure
insulation resistance?
A. Clamp meter
B. Megohmmeter
C. Frequency meter
D. Wattmeter
Correct answer: Megohmmeter
Rationale: A megohmmeter, commonly called a megger,
applies a relatively high DC test voltage to measure
insulation resistance.
4. What is Ohm's Law?
A. P = EI
B. E = IR
C. I = ER
D. R = EI
Correct answer: E = IR
Rationale: Ohm's Law states that voltage equals current
multiplied by resistance: E = I × R.
5. A 480-volt three-phase motor draws 20 amperes at a
power factor of 0.85. Which formula is used to calculate
its approximate input power?
A. P = EI
B. P = I²R
C. P = √3 × E × I × PF
D. P = E/R
Correct answer: P = √3 × E × I × PF
,Rationale: For a three-phase load, real power is
calculated using √3 × line voltage × line current ×
power factor.
6. What is the primary purpose of a transformer?
A. To convert AC to DC
B. To change AC voltage levels
C. To increase frequency
D. To eliminate current
Correct answer: To change AC voltage levels
Rationale: A transformer transfers electrical energy
between windings through electromagnetic induction
and can step voltage up or down.
7. Which transformer winding normally has more turns
in a step-down transformer?
A. Secondary winding
B. Primary winding
C. Grounding winding
D. Shield winding
Correct answer: Primary winding
Rationale: In a step-down transformer, the primary has
more turns than the secondary, producing a lower
secondary voltage.
8. What happens to conductor resistance as conductor
temperature increases?
A. It generally decreases
B. It generally increases
C. It becomes zero
D. It remains exactly constant
, Correct answer: It generally increases
Rationale: The resistance of most metallic conductors
increases as temperature rises.
9. Which device is commonly used to protect a motor
against sustained overload?
A. Motor overload relay
B. Pilot light
C. Disconnect handle
D. Transformer
Correct answer: Motor overload relay
Rationale: Motor overload protection responds to
excessive motor current over time and protects the
motor from overheating due to overload conditions.
10. What is the purpose of a motor starter?
A. Only to measure voltage
B. To start and stop a motor and provide control/protection
functions
C. To increase motor frequency
D. To replace the motor bearings
Correct answer: To start and stop a motor and provide
control/protection functions
Rationale: A motor starter typically combines a
contactor or controller with overload protection and
permits safe control of the motor.
11. What is the purpose of a disconnecting means for
industrial equipment?
A. To increase motor speed
B. To provide a means of disconnecting the equipment from its
Electrical Contractor Practice
Exam | Questions, Verified
Answers & Detailed Rationales |
Complete Contractor License
Exam Prep Study Guide |
Updated 2026
1. What is the primary purpose of an equipment
grounding conductor?
A. To carry normal operating current
B. To increase circuit voltage
C. To provide a low-impedance path for fault current
D. To reduce conductor resistance
Correct answer: To provide a low-impedance path for
fault current
Rationale: The equipment grounding conductor provides
a low-impedance path for fault current so that the
overcurrent protective device can operate quickly and
disconnect the faulted circuit.
2. In a balanced three-phase system, what is the phase
relationship between the three phase voltages?
A. 60 degrees
B. 90 degrees
C. 120 degrees
D. 180 degrees
Correct answer: 120 degrees
,Rationale: The three phase voltages in a balanced three-
phase system are separated by 120 electrical degrees.
3. Which instrument is normally used to measure
insulation resistance?
A. Clamp meter
B. Megohmmeter
C. Frequency meter
D. Wattmeter
Correct answer: Megohmmeter
Rationale: A megohmmeter, commonly called a megger,
applies a relatively high DC test voltage to measure
insulation resistance.
4. What is Ohm's Law?
A. P = EI
B. E = IR
C. I = ER
D. R = EI
Correct answer: E = IR
Rationale: Ohm's Law states that voltage equals current
multiplied by resistance: E = I × R.
5. A 480-volt three-phase motor draws 20 amperes at a
power factor of 0.85. Which formula is used to calculate
its approximate input power?
A. P = EI
B. P = I²R
C. P = √3 × E × I × PF
D. P = E/R
Correct answer: P = √3 × E × I × PF
,Rationale: For a three-phase load, real power is
calculated using √3 × line voltage × line current ×
power factor.
6. What is the primary purpose of a transformer?
A. To convert AC to DC
B. To change AC voltage levels
C. To increase frequency
D. To eliminate current
Correct answer: To change AC voltage levels
Rationale: A transformer transfers electrical energy
between windings through electromagnetic induction
and can step voltage up or down.
7. Which transformer winding normally has more turns
in a step-down transformer?
A. Secondary winding
B. Primary winding
C. Grounding winding
D. Shield winding
Correct answer: Primary winding
Rationale: In a step-down transformer, the primary has
more turns than the secondary, producing a lower
secondary voltage.
8. What happens to conductor resistance as conductor
temperature increases?
A. It generally decreases
B. It generally increases
C. It becomes zero
D. It remains exactly constant
, Correct answer: It generally increases
Rationale: The resistance of most metallic conductors
increases as temperature rises.
9. Which device is commonly used to protect a motor
against sustained overload?
A. Motor overload relay
B. Pilot light
C. Disconnect handle
D. Transformer
Correct answer: Motor overload relay
Rationale: Motor overload protection responds to
excessive motor current over time and protects the
motor from overheating due to overload conditions.
10. What is the purpose of a motor starter?
A. Only to measure voltage
B. To start and stop a motor and provide control/protection
functions
C. To increase motor frequency
D. To replace the motor bearings
Correct answer: To start and stop a motor and provide
control/protection functions
Rationale: A motor starter typically combines a
contactor or controller with overload protection and
permits safe control of the motor.
11. What is the purpose of a disconnecting means for
industrial equipment?
A. To increase motor speed
B. To provide a means of disconnecting the equipment from its
