NYC DCAS Electrician Practice Exam
Questions and Answers with Rationales
Latest Versions
Question 1
A 120-volt circuit has a resistance of 20 ohms. What current flows through the
circuit?
A. 3 A
B. 6 A
C. 10 A
D. 24 A
Correct Answer: B. 6 A
Rationale:
Ohm’s law states:
[
I = \frac{V}{R}
]
Therefore:
[
I = \frac{120}{20}=6A
]
The circuit current is 6 amperes.
Question 2
What is the primary purpose of a circuit breaker?
A. Increase circuit voltage
B. Reduce conductor resistance
,C. Protect the circuit from excessive current
D. Improve power factor
Correct Answer: C. Protect the circuit from excessive current
Rationale:
A circuit breaker is an overcurrent protective device. It opens the circuit when
current exceeds the permitted level for the circuit, helping protect conductors and
equipment from damage and reducing fire hazards.
Question 3
Which instrument is normally used to measure electrical resistance?
A. Ammeter
B. Voltmeter
C. Ohmmeter
D. Frequency meter
Correct Answer: C. Ohmmeter
Rationale:
An ohmmeter measures resistance in ohms (Ω). Resistance measurements should
normally be made on a de-energized circuit because the meter applies a test voltage
to determine resistance.
Question 4
A 120-V load draws 10 A. Approximately how much power does the load
consume?
A. 12 W
B. 120 W
C. 1,200 W
D. 12,000 W
Correct Answer: C. 1,200 W
,Rationale:
For a simple resistive load:
[
P=V\times I
]
[
P=120\times10=1,200W
]
Therefore, the load consumes approximately 1,200 watts.
Question 5
What is the main purpose of equipment grounding?
A. To increase normal operating voltage
B. To provide a low-impedance path for fault current
C. To increase circuit resistance
D. To eliminate the need for overcurrent protection
Correct Answer: B. To provide a low-impedance path for fault current
Rationale:
The equipment grounding system provides a path for fault current so that
protective devices can operate promptly when a fault energizes normally non-
current-carrying metal parts.
Question 6
Which device is specifically designed to provide personnel protection against
certain ground-fault conditions?
A. GFCI
B. Transformer
, C. Contactor
D. Disconnect switch
Correct Answer: A. GFCI
Rationale:
A ground-fault circuit interrupter (GFCI) monitors current leaving and
returning through the intended circuit conductors. When it detects an imbalance
indicating a ground fault, it interrupts power rapidly.
Question 7
In a series circuit, the current through each series component is:
A. Different at every component
B. Zero at the first component
C. The same through all components
D. Always equal to the voltage
Correct Answer: C. The same through all components
Rationale:
A series circuit has only one path for current. Therefore, the same current flows
through every component in the series circuit.
Question 8
What happens to total resistance when additional resistors are connected in series?
A. It decreases
B. It remains unchanged
C. It increases
D. It becomes zero
Correct Answer: C. It increases
Rationale:
For resistors connected in series:
Questions and Answers with Rationales
Latest Versions
Question 1
A 120-volt circuit has a resistance of 20 ohms. What current flows through the
circuit?
A. 3 A
B. 6 A
C. 10 A
D. 24 A
Correct Answer: B. 6 A
Rationale:
Ohm’s law states:
[
I = \frac{V}{R}
]
Therefore:
[
I = \frac{120}{20}=6A
]
The circuit current is 6 amperes.
Question 2
What is the primary purpose of a circuit breaker?
A. Increase circuit voltage
B. Reduce conductor resistance
,C. Protect the circuit from excessive current
D. Improve power factor
Correct Answer: C. Protect the circuit from excessive current
Rationale:
A circuit breaker is an overcurrent protective device. It opens the circuit when
current exceeds the permitted level for the circuit, helping protect conductors and
equipment from damage and reducing fire hazards.
Question 3
Which instrument is normally used to measure electrical resistance?
A. Ammeter
B. Voltmeter
C. Ohmmeter
D. Frequency meter
Correct Answer: C. Ohmmeter
Rationale:
An ohmmeter measures resistance in ohms (Ω). Resistance measurements should
normally be made on a de-energized circuit because the meter applies a test voltage
to determine resistance.
Question 4
A 120-V load draws 10 A. Approximately how much power does the load
consume?
A. 12 W
B. 120 W
C. 1,200 W
D. 12,000 W
Correct Answer: C. 1,200 W
,Rationale:
For a simple resistive load:
[
P=V\times I
]
[
P=120\times10=1,200W
]
Therefore, the load consumes approximately 1,200 watts.
Question 5
What is the main purpose of equipment grounding?
A. To increase normal operating voltage
B. To provide a low-impedance path for fault current
C. To increase circuit resistance
D. To eliminate the need for overcurrent protection
Correct Answer: B. To provide a low-impedance path for fault current
Rationale:
The equipment grounding system provides a path for fault current so that
protective devices can operate promptly when a fault energizes normally non-
current-carrying metal parts.
Question 6
Which device is specifically designed to provide personnel protection against
certain ground-fault conditions?
A. GFCI
B. Transformer
, C. Contactor
D. Disconnect switch
Correct Answer: A. GFCI
Rationale:
A ground-fault circuit interrupter (GFCI) monitors current leaving and
returning through the intended circuit conductors. When it detects an imbalance
indicating a ground fault, it interrupts power rapidly.
Question 7
In a series circuit, the current through each series component is:
A. Different at every component
B. Zero at the first component
C. The same through all components
D. Always equal to the voltage
Correct Answer: C. The same through all components
Rationale:
A series circuit has only one path for current. Therefore, the same current flows
through every component in the series circuit.
Question 8
What happens to total resistance when additional resistors are connected in series?
A. It decreases
B. It remains unchanged
C. It increases
D. It becomes zero
Correct Answer: C. It increases
Rationale:
For resistors connected in series:
