CO Class E Electrical Contractor Exam
Questions and Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf
1. Which document typically establishes the specific electrical work
to be performed on a construction project?
A. Material safety data sheet
B. Building permit application
C. Electrical plans and specifications
D. Equipment warranty
Rationale: Electrical plans and specifications define the scope, system
requirements, equipment, wiring methods, and other details needed
to perform the electrical installation correctly.
2. What is the primary purpose of an electrical service disconnect?
,A. To increase circuit voltage
B. To measure energy consumption
C. To disconnect the premises from the electrical supply
D. To regulate transformer temperature
Rationale: The service disconnect provides a means of disconnecting
the electrical installation from the source of supply so that the system
can be serviced or shut down safely.
3. Which unit is used to measure electrical current?
A. Volt
B. Ohm
C. Watt
D. Ampere
Rationale: The ampere, commonly called an amp, is the unit of
electrical current. Voltage measures electrical potential, resistance is
measured in ohms, and power is measured in watts.
4. What is the primary function of a circuit breaker?
A. Increase conductor resistance
B. Reduce system voltage
C. Open a circuit when excessive current occurs
D. Store electrical energy
,Rationale: A circuit breaker protects conductors and equipment by
interrupting current when an overload or short circuit causes current
to exceed the circuit's safe capacity.
5. Which electrical quantity is measured in volts?
A. Current
B. Resistance
C. Power
D. Electrical potential difference
Rationale: Voltage represents electrical potential difference between
two points and is measured in volts.
6. What is the purpose of equipment grounding?
A. To increase normal operating current
B. To provide a low-resistance path for fault current
C. To increase circuit voltage
D. To reduce conductor size
Rationale: Equipment grounding provides a conductive path that
helps fault current return to the source, allowing protective devices to
operate and reducing shock hazards.
7. Which formula represents Ohm's Law?
, A. P = I²R
B. P = VI
C. V = IR
D. E = mc²
Rationale: Ohm's Law states that voltage equals current multiplied by
resistance. This relationship is expressed as V = I × R.
8. A 120-volt circuit supplies a 10-ampere load. What is the
approximate power consumption?
A. 12 watts
B. 120 watts
C. 1,200 watts
D. 12,000 watts
Rationale: Electrical power in a simple single-phase circuit can be
calculated as P = V × I. Therefore, 120 × 10 = 1,200 watts.
9. What is the main purpose of a junction box?
A. To increase circuit voltage
B. To enclose and protect electrical splices and connections
C. To replace circuit breakers
D. To provide water pressure
Questions and Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf
1. Which document typically establishes the specific electrical work
to be performed on a construction project?
A. Material safety data sheet
B. Building permit application
C. Electrical plans and specifications
D. Equipment warranty
Rationale: Electrical plans and specifications define the scope, system
requirements, equipment, wiring methods, and other details needed
to perform the electrical installation correctly.
2. What is the primary purpose of an electrical service disconnect?
,A. To increase circuit voltage
B. To measure energy consumption
C. To disconnect the premises from the electrical supply
D. To regulate transformer temperature
Rationale: The service disconnect provides a means of disconnecting
the electrical installation from the source of supply so that the system
can be serviced or shut down safely.
3. Which unit is used to measure electrical current?
A. Volt
B. Ohm
C. Watt
D. Ampere
Rationale: The ampere, commonly called an amp, is the unit of
electrical current. Voltage measures electrical potential, resistance is
measured in ohms, and power is measured in watts.
4. What is the primary function of a circuit breaker?
A. Increase conductor resistance
B. Reduce system voltage
C. Open a circuit when excessive current occurs
D. Store electrical energy
,Rationale: A circuit breaker protects conductors and equipment by
interrupting current when an overload or short circuit causes current
to exceed the circuit's safe capacity.
5. Which electrical quantity is measured in volts?
A. Current
B. Resistance
C. Power
D. Electrical potential difference
Rationale: Voltage represents electrical potential difference between
two points and is measured in volts.
6. What is the purpose of equipment grounding?
A. To increase normal operating current
B. To provide a low-resistance path for fault current
C. To increase circuit voltage
D. To reduce conductor size
Rationale: Equipment grounding provides a conductive path that
helps fault current return to the source, allowing protective devices to
operate and reducing shock hazards.
7. Which formula represents Ohm's Law?
, A. P = I²R
B. P = VI
C. V = IR
D. E = mc²
Rationale: Ohm's Law states that voltage equals current multiplied by
resistance. This relationship is expressed as V = I × R.
8. A 120-volt circuit supplies a 10-ampere load. What is the
approximate power consumption?
A. 12 watts
B. 120 watts
C. 1,200 watts
D. 12,000 watts
Rationale: Electrical power in a simple single-phase circuit can be
calculated as P = V × I. Therefore, 120 × 10 = 1,200 watts.
9. What is the main purpose of a junction box?
A. To increase circuit voltage
B. To enclose and protect electrical splices and connections
C. To replace circuit breakers
D. To provide water pressure
