CT Limited Electrical Contractor (E-3) Exam
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A|
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1. What is the primary purpose of a circuit breaker in an electrical
circuit?
A. To increase voltage
B. To reduce resistance
C. To interrupt current when an overcurrent occurs
D. To improve power factor
Rationale: A circuit breaker is designed to automatically open a circuit
when current exceeds a safe level. This protects conductors and
equipment from overheating and reduces the risk of fire or damage.
2. Which unit is used to measure electrical current?
A. Volt
B. Ohm
,C. Watt
D. Ampere
Rationale: Electrical current is measured in amperes (amps). Voltage is
measured in volts, resistance in ohms, and power in watts.
3. What is the purpose of grounding an electrical system?
A. To increase circuit voltage
B. To reduce conductor size
C. To provide a low-impedance path for fault current
D. To eliminate all electrical resistance
Rationale: Grounding provides a safe path for fault current to return
to the source, allowing protective devices to operate and helping
prevent dangerous voltage from remaining on exposed metal parts.
4. Which device is specifically designed to protect people from
electric shock caused by ground-fault current?
A. Fuse
B. Transformer
C. Ground-fault circuit interrupter (GFCI)
D. Disconnect switch
,Rationale: A GFCI monitors the current leaving and returning through
a circuit. If it detects an imbalance indicating current may be flowing
through a person or unintended path, it quickly disconnects the circuit.
5. What is the basic relationship expressed by Ohm's law?
A. P = I/R
B. E = I × R
C. E = P × R
D. R = E × I
Rationale: Ohm's law states that voltage (E) equals current (I)
multiplied by resistance (R). This relationship is fundamental to
calculating electrical circuit values.
6. A 120-volt circuit supplies a 10-ohm load. Approximately how
much current flows through the load?
A. 1.2 amperes
B. 12 amperes
C. 120 amperes
D. 1,200 amperes
Rationale: Using Ohm's law, I = E/R. Therefore, 120 volts ÷ 10 ohms =
12 amperes.
7. What is the main purpose of a disconnecting means?
, A. To increase available fault current
B. To regulate frequency
C. To disconnect electrical equipment from its source of supply
D. To increase conductor ampacity
Rationale: A disconnecting means allows equipment to be isolated
from its electrical supply so it can be safely serviced, maintained, or
repaired.
8. Which conductor normally carries current back to the source on a
standard single-phase circuit?
A. Equipment grounding conductor
B. Bonding jumper
C. Grounded (neutral) conductor
D. Grounding electrode conductor
Rationale: In a typical single-phase circuit, the grounded conductor
provides the normal return path for current to the source. The
equipment grounding conductor is intended primarily for fault-current
conditions.
9. What is the primary function of an equipment grounding
conductor?
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A|
Instant Download Pdf
1. What is the primary purpose of a circuit breaker in an electrical
circuit?
A. To increase voltage
B. To reduce resistance
C. To interrupt current when an overcurrent occurs
D. To improve power factor
Rationale: A circuit breaker is designed to automatically open a circuit
when current exceeds a safe level. This protects conductors and
equipment from overheating and reduces the risk of fire or damage.
2. Which unit is used to measure electrical current?
A. Volt
B. Ohm
,C. Watt
D. Ampere
Rationale: Electrical current is measured in amperes (amps). Voltage is
measured in volts, resistance in ohms, and power in watts.
3. What is the purpose of grounding an electrical system?
A. To increase circuit voltage
B. To reduce conductor size
C. To provide a low-impedance path for fault current
D. To eliminate all electrical resistance
Rationale: Grounding provides a safe path for fault current to return
to the source, allowing protective devices to operate and helping
prevent dangerous voltage from remaining on exposed metal parts.
4. Which device is specifically designed to protect people from
electric shock caused by ground-fault current?
A. Fuse
B. Transformer
C. Ground-fault circuit interrupter (GFCI)
D. Disconnect switch
,Rationale: A GFCI monitors the current leaving and returning through
a circuit. If it detects an imbalance indicating current may be flowing
through a person or unintended path, it quickly disconnects the circuit.
5. What is the basic relationship expressed by Ohm's law?
A. P = I/R
B. E = I × R
C. E = P × R
D. R = E × I
Rationale: Ohm's law states that voltage (E) equals current (I)
multiplied by resistance (R). This relationship is fundamental to
calculating electrical circuit values.
6. A 120-volt circuit supplies a 10-ohm load. Approximately how
much current flows through the load?
A. 1.2 amperes
B. 12 amperes
C. 120 amperes
D. 1,200 amperes
Rationale: Using Ohm's law, I = E/R. Therefore, 120 volts ÷ 10 ohms =
12 amperes.
7. What is the main purpose of a disconnecting means?
, A. To increase available fault current
B. To regulate frequency
C. To disconnect electrical equipment from its source of supply
D. To increase conductor ampacity
Rationale: A disconnecting means allows equipment to be isolated
from its electrical supply so it can be safely serviced, maintained, or
repaired.
8. Which conductor normally carries current back to the source on a
standard single-phase circuit?
A. Equipment grounding conductor
B. Bonding jumper
C. Grounded (neutral) conductor
D. Grounding electrode conductor
Rationale: In a typical single-phase circuit, the grounded conductor
provides the normal return path for current to the source. The
equipment grounding conductor is intended primarily for fault-current
conditions.
9. What is the primary function of an equipment grounding
conductor?
