NYC DCAS Electrician Exam Questions
and Answers with Rationales Latest
Versions
Question 1
A 120-volt branch circuit supplies a 1,500-watt electric heater.
Approximately how much current does the heater draw?
A. 8.0 A
B. 10.0 A
C. 12.5 A
D. 15.0 A
Correct Answer: C. 12.5 A
Explanation:
Ohm's law and the power formula can be used to determine current:
[
I = \frac{P}{V}
]
[
I = \frac{1500W}{120V}=12.5A
]
Therefore, the heater draws approximately 12.5 amperes.
Why the other answers are incorrect:
• A. 8.0 A: Would correspond to about 960 W at 120 V.
• B. 10.0 A: Would correspond to 1,200 W.
, • D. 15.0 A: Would correspond to 1,800 W.
Key point: For a purely resistive load, current can be calculated by
dividing watts by volts.
Question 2
What is the primary purpose of an overcurrent protective device such as
a circuit breaker or fuse?
A. To increase circuit voltage
B. To protect conductors from excessive current
C. To improve power factor
D. To provide additional electrical energy
Correct Answer: B. To protect conductors from excessive current
Rationale:
A circuit breaker or fuse is designed to interrupt a circuit when current
becomes excessive. Excessive current can cause conductors to overheat,
potentially damaging insulation and creating a fire hazard.
A fuse generally operates by melting its element when excessive current
flows. A circuit breaker opens its contacts when its trip mechanism
detects an overcurrent condition.
Key point: Overcurrent protection primarily protects conductors and
equipment from damaging excessive current.
Question 3
An electrician is working on a circuit that has been de-energized. Which
action is most important before beginning work?
,A. Assume the circuit is dead because the breaker is off
B. Verify the absence of voltage with an appropriate test instrument
C. Remove the grounding conductor
D. Replace the breaker with a larger one
Correct Answer: B. Verify the absence of voltage with an
appropriate test instrument
Rationale:
Turning off a breaker is not, by itself, sufficient confirmation that a
circuit is safe to work on. The electrician should follow appropriate
lockout/tagout and electrical safety procedures and test for absence of
voltage using a properly rated instrument.
Unexpected energization, mislabeled circuits, backfeed, or incorrect
breaker identification can create serious hazards.
Key point: Test before you touch.
Question 4
What is the purpose of a grounding electrode system?
A. To increase normal operating current
B. To provide a connection to earth for specified electrical purposes
C. To replace all circuit breakers
D. To increase branch-circuit voltage
Correct Answer: B. To provide a connection to earth for specified
electrical purposes
Rationale:
The grounding electrode system connects the electrical system to earth
through recognized grounding electrodes. This connection is part of the
overall grounding and bonding system and serves purposes such as
, stabilizing system voltage to earth and providing a path for certain fault
or transient conditions.
It is important to distinguish grounding from bonding. Bonding
connects normally non-current-carrying conductive parts together and to
the grounding system to establish an effective fault-current path.
Question 5
A copper conductor has a resistance of 4 ohms and is connected to a
120-volt source. What current will flow through the conductor?
A. 15 A
B. 20 A
C. 30 A
D. 480 A
Correct Answer: A. 30 A
Rationale:
Using Ohm's law:
[
I=\frac{V}{R}
]
[
I=\frac{120}{4}=30A
]
Therefore, the current is 30 amperes.
Correction check: The correct option is C. 30 A.
Key point: Remember the three fundamental relationships:
and Answers with Rationales Latest
Versions
Question 1
A 120-volt branch circuit supplies a 1,500-watt electric heater.
Approximately how much current does the heater draw?
A. 8.0 A
B. 10.0 A
C. 12.5 A
D. 15.0 A
Correct Answer: C. 12.5 A
Explanation:
Ohm's law and the power formula can be used to determine current:
[
I = \frac{P}{V}
]
[
I = \frac{1500W}{120V}=12.5A
]
Therefore, the heater draws approximately 12.5 amperes.
Why the other answers are incorrect:
• A. 8.0 A: Would correspond to about 960 W at 120 V.
• B. 10.0 A: Would correspond to 1,200 W.
, • D. 15.0 A: Would correspond to 1,800 W.
Key point: For a purely resistive load, current can be calculated by
dividing watts by volts.
Question 2
What is the primary purpose of an overcurrent protective device such as
a circuit breaker or fuse?
A. To increase circuit voltage
B. To protect conductors from excessive current
C. To improve power factor
D. To provide additional electrical energy
Correct Answer: B. To protect conductors from excessive current
Rationale:
A circuit breaker or fuse is designed to interrupt a circuit when current
becomes excessive. Excessive current can cause conductors to overheat,
potentially damaging insulation and creating a fire hazard.
A fuse generally operates by melting its element when excessive current
flows. A circuit breaker opens its contacts when its trip mechanism
detects an overcurrent condition.
Key point: Overcurrent protection primarily protects conductors and
equipment from damaging excessive current.
Question 3
An electrician is working on a circuit that has been de-energized. Which
action is most important before beginning work?
,A. Assume the circuit is dead because the breaker is off
B. Verify the absence of voltage with an appropriate test instrument
C. Remove the grounding conductor
D. Replace the breaker with a larger one
Correct Answer: B. Verify the absence of voltage with an
appropriate test instrument
Rationale:
Turning off a breaker is not, by itself, sufficient confirmation that a
circuit is safe to work on. The electrician should follow appropriate
lockout/tagout and electrical safety procedures and test for absence of
voltage using a properly rated instrument.
Unexpected energization, mislabeled circuits, backfeed, or incorrect
breaker identification can create serious hazards.
Key point: Test before you touch.
Question 4
What is the purpose of a grounding electrode system?
A. To increase normal operating current
B. To provide a connection to earth for specified electrical purposes
C. To replace all circuit breakers
D. To increase branch-circuit voltage
Correct Answer: B. To provide a connection to earth for specified
electrical purposes
Rationale:
The grounding electrode system connects the electrical system to earth
through recognized grounding electrodes. This connection is part of the
overall grounding and bonding system and serves purposes such as
, stabilizing system voltage to earth and providing a path for certain fault
or transient conditions.
It is important to distinguish grounding from bonding. Bonding
connects normally non-current-carrying conductive parts together and to
the grounding system to establish an effective fault-current path.
Question 5
A copper conductor has a resistance of 4 ohms and is connected to a
120-volt source. What current will flow through the conductor?
A. 15 A
B. 20 A
C. 30 A
D. 480 A
Correct Answer: A. 30 A
Rationale:
Using Ohm's law:
[
I=\frac{V}{R}
]
[
I=\frac{120}{4}=30A
]
Therefore, the current is 30 amperes.
Correction check: The correct option is C. 30 A.
Key point: Remember the three fundamental relationships:
