Minnesota Class B Master Electrician
Examination Questions and Correct Answers
(Verified Answers) Plus Rationale 2027 Q&A|
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1. What is the primary purpose of overcurrent protection in an
electrical circuit?
A. To increase circuit voltage
B. To improve power factor
C. To protect conductors and equipment from excessive current
D. To eliminate all electrical noise
Rationale: Overcurrent protection devices such as fuses and circuit
breakers are designed to interrupt current when it exceeds a safe level.
This helps prevent conductor overheating, equipment damage, and fire
hazards.
2. Which conductor is normally identified as the grounded (neutral)
conductor in a typical branch circuit?
,A. Green
B. Red
C. Black
D. White or gray
Rationale: The National Electrical Code generally identifies grounded
circuit conductors with white or gray insulation or markings. Green and
bare conductors are generally reserved for equipment grounding
purposes.
3. What is the primary function of an equipment grounding
conductor?
A. Carry normal circuit current
B. Reduce operating voltage
C. Provide a low-impedance path for fault current
D. Increase circuit resistance
Rationale: The equipment grounding conductor provides a path for fault
current back to the source. This facilitates operation of the overcurrent
protective device and helps keep exposed metal parts at a safer
potential.
4. A 120-volt circuit supplies a 1,800-watt resistive load.
Approximately how much current does the load draw?
,A. 7.5 A
B. 10 A
C. 15 A
D. 20 A
Rationale: For a resistive load, current can be calculated using I = P ÷ E.
Thus, 1,800 watts ÷ 120 volts = 15 amperes.
5. What is the purpose of a circuit breaker?
A. To regulate normal voltage
B. To automatically interrupt a circuit when excessive current occurs
C. To increase available current
D. To provide a neutral connection
Rationale: A circuit breaker is an overcurrent protective device. It opens
the circuit when current reaches a level that could damage conductors
or equipment.
6. Which formula represents Ohm's law?
A. P = IE
B. I = PR
C. E = IR
D. R = PI
, Rationale: Ohm's law states that voltage (E) equals current (I) multiplied
by resistance (R). The formula can also be rearranged to calculate
current or resistance.
7. What is the resistance of a circuit carrying 10 amperes at 120
volts?
A. 6 ohms
B. 10 ohms
C. 12 ohms
D. 20 ohms
Rationale: Using R = E ÷ I, divide 120 volts by 10 amperes. The result is
12 ohms.
8. Which device is specifically designed to provide personnel
protection against ground-fault shock hazards?
A. AFCI
B. Disconnect switch
C. Surge protector
D. GFCI
Rationale: A ground-fault circuit interrupter monitors current leaving
and returning through the circuit. When it detects an imbalance
indicating leakage current, it rapidly opens the circuit.
Examination Questions and Correct Answers
(Verified Answers) Plus Rationale 2027 Q&A|
Instant Download Pdf
1. What is the primary purpose of overcurrent protection in an
electrical circuit?
A. To increase circuit voltage
B. To improve power factor
C. To protect conductors and equipment from excessive current
D. To eliminate all electrical noise
Rationale: Overcurrent protection devices such as fuses and circuit
breakers are designed to interrupt current when it exceeds a safe level.
This helps prevent conductor overheating, equipment damage, and fire
hazards.
2. Which conductor is normally identified as the grounded (neutral)
conductor in a typical branch circuit?
,A. Green
B. Red
C. Black
D. White or gray
Rationale: The National Electrical Code generally identifies grounded
circuit conductors with white or gray insulation or markings. Green and
bare conductors are generally reserved for equipment grounding
purposes.
3. What is the primary function of an equipment grounding
conductor?
A. Carry normal circuit current
B. Reduce operating voltage
C. Provide a low-impedance path for fault current
D. Increase circuit resistance
Rationale: The equipment grounding conductor provides a path for fault
current back to the source. This facilitates operation of the overcurrent
protective device and helps keep exposed metal parts at a safer
potential.
4. A 120-volt circuit supplies a 1,800-watt resistive load.
Approximately how much current does the load draw?
,A. 7.5 A
B. 10 A
C. 15 A
D. 20 A
Rationale: For a resistive load, current can be calculated using I = P ÷ E.
Thus, 1,800 watts ÷ 120 volts = 15 amperes.
5. What is the purpose of a circuit breaker?
A. To regulate normal voltage
B. To automatically interrupt a circuit when excessive current occurs
C. To increase available current
D. To provide a neutral connection
Rationale: A circuit breaker is an overcurrent protective device. It opens
the circuit when current reaches a level that could damage conductors
or equipment.
6. Which formula represents Ohm's law?
A. P = IE
B. I = PR
C. E = IR
D. R = PI
, Rationale: Ohm's law states that voltage (E) equals current (I) multiplied
by resistance (R). The formula can also be rearranged to calculate
current or resistance.
7. What is the resistance of a circuit carrying 10 amperes at 120
volts?
A. 6 ohms
B. 10 ohms
C. 12 ohms
D. 20 ohms
Rationale: Using R = E ÷ I, divide 120 volts by 10 amperes. The result is
12 ohms.
8. Which device is specifically designed to provide personnel
protection against ground-fault shock hazards?
A. AFCI
B. Disconnect switch
C. Surge protector
D. GFCI
Rationale: A ground-fault circuit interrupter monitors current leaving
and returning through the circuit. When it detects an imbalance
indicating leakage current, it rapidly opens the circuit.
