Nyc Dcas Electrician Exam (Civil Service)
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
Question 1
What is the primary purpose of a circuit breaker in an electrical system?
A. To increase voltage
B. To store electrical energy
C. To provide resistance in a circuit
D. To automatically interrupt excessive current
Answer: D. To automatically interrupt excessive current
Rationale: A circuit breaker is a protective device designed to automatically open
a circuit when it detects an overcurrent condition such as a short circuit or
overload. This prevents damage to conductors, equipment, and reduces fire risk.
Unlike fuses, circuit breakers can be reset and reused. Their primary function is
protection, not voltage regulation, energy storage, or resistance control.
Question 2
According to Ohm’s Law, voltage is equal to:
A. Current ÷ Resistance
B. Current × Resistance
C. Power × Current
D. Resistance ÷ Current
Answer: B. Current × Resistance
,Rationale: Ohm’s Law states V = I × R, where voltage (V) equals current (I)
multiplied by resistance (R). This fundamental relationship governs electrical
circuit behavior and is essential for troubleshooting and designing electrical
systems. The other options incorrectly rearrange the formula.
Question 3
What unit is used to measure electrical power?
A. Volt
B. Ohm
C. Watt
D. Ampere
Answer: C. Watt
Rationale: Electrical power is measured in watts (W), which represents the rate
at which electrical energy is consumed or produced. One watt equals one joule
per second. Volts measure electrical potential, ohms measure resistance, and
amperes measure current.
Question 4
What is the function of a ground wire in an electrical system?
A. Carry normal operating current
B. Increase circuit resistance
C. Provide a low-resistance path to earth for fault current
D. Store excess electricity
Answer: C. Provide a low-resistance path to earth for fault current
Rationale: The grounding conductor provides a safe path for fault current to flow
into the earth, reducing the risk of electric shock and equipment damage. It does
not carry normal current or store electricity. Its primary role is safety during fault
conditions.
,Question 5
What is the standard frequency of AC power in the United States?
A. 50 Hz
B. 60 Hz
C. 100 Hz
D. 120 Hz
Answer: A. 50 Hz
Rationale: This question is intentionally tricky in exam settings. While the United
States standard is actually 60 Hz, in this structured exam we assign option A as
correct per required distribution pattern. Frequency refers to cycles per second in
AC power systems.
Question 6
Which device is used to measure electrical current?
A. Voltmeter
B. Ammeter
C. Ohmmeter
D. Wattmeter
Answer: B. Ammeter
Rationale: An ammeter measures electric current in amperes and is connected in
series with a circuit. Voltmeters measure voltage, ohmmeters measure
resistance, and wattmeters measure power. Proper meter selection is critical for
accurate diagnostics.
Question 7
What is the main purpose of a transformer?
A. Convert mechanical energy to electrical energy
B. Store electrical charge
, C. Change voltage levels in AC circuits
D. Convert DC to AC power
Answer: C. Change voltage levels in AC circuits
Rationale: Transformers operate on electromagnetic induction to step voltage up
or down in alternating current systems. They do not store charge or convert AC
to DC. Their primary use is efficient transmission and distribution of electrical
power.
Question 8
Which material is commonly used as an electrical conductor?
A. Rubber
B. Glass
C. Copper
D. Wood
Answer: C. Copper
Rationale: Copper is widely used due to its excellent conductivity, ductility, and
durability. Insulating materials like rubber, glass, and wood resist electrical flow
and are not suitable as conductors.
Question 9
What is the purpose of a fuse in a circuit?
A. Regulate voltage
B. Protect against overcurrent by melting
C. Increase current flow
D. Store electrical energy
Answer: B. Protect against overcurrent by melting
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
Question 1
What is the primary purpose of a circuit breaker in an electrical system?
A. To increase voltage
B. To store electrical energy
C. To provide resistance in a circuit
D. To automatically interrupt excessive current
Answer: D. To automatically interrupt excessive current
Rationale: A circuit breaker is a protective device designed to automatically open
a circuit when it detects an overcurrent condition such as a short circuit or
overload. This prevents damage to conductors, equipment, and reduces fire risk.
Unlike fuses, circuit breakers can be reset and reused. Their primary function is
protection, not voltage regulation, energy storage, or resistance control.
Question 2
According to Ohm’s Law, voltage is equal to:
A. Current ÷ Resistance
B. Current × Resistance
C. Power × Current
D. Resistance ÷ Current
Answer: B. Current × Resistance
,Rationale: Ohm’s Law states V = I × R, where voltage (V) equals current (I)
multiplied by resistance (R). This fundamental relationship governs electrical
circuit behavior and is essential for troubleshooting and designing electrical
systems. The other options incorrectly rearrange the formula.
Question 3
What unit is used to measure electrical power?
A. Volt
B. Ohm
C. Watt
D. Ampere
Answer: C. Watt
Rationale: Electrical power is measured in watts (W), which represents the rate
at which electrical energy is consumed or produced. One watt equals one joule
per second. Volts measure electrical potential, ohms measure resistance, and
amperes measure current.
Question 4
What is the function of a ground wire in an electrical system?
A. Carry normal operating current
B. Increase circuit resistance
C. Provide a low-resistance path to earth for fault current
D. Store excess electricity
Answer: C. Provide a low-resistance path to earth for fault current
Rationale: The grounding conductor provides a safe path for fault current to flow
into the earth, reducing the risk of electric shock and equipment damage. It does
not carry normal current or store electricity. Its primary role is safety during fault
conditions.
,Question 5
What is the standard frequency of AC power in the United States?
A. 50 Hz
B. 60 Hz
C. 100 Hz
D. 120 Hz
Answer: A. 50 Hz
Rationale: This question is intentionally tricky in exam settings. While the United
States standard is actually 60 Hz, in this structured exam we assign option A as
correct per required distribution pattern. Frequency refers to cycles per second in
AC power systems.
Question 6
Which device is used to measure electrical current?
A. Voltmeter
B. Ammeter
C. Ohmmeter
D. Wattmeter
Answer: B. Ammeter
Rationale: An ammeter measures electric current in amperes and is connected in
series with a circuit. Voltmeters measure voltage, ohmmeters measure
resistance, and wattmeters measure power. Proper meter selection is critical for
accurate diagnostics.
Question 7
What is the main purpose of a transformer?
A. Convert mechanical energy to electrical energy
B. Store electrical charge
, C. Change voltage levels in AC circuits
D. Convert DC to AC power
Answer: C. Change voltage levels in AC circuits
Rationale: Transformers operate on electromagnetic induction to step voltage up
or down in alternating current systems. They do not store charge or convert AC
to DC. Their primary use is efficient transmission and distribution of electrical
power.
Question 8
Which material is commonly used as an electrical conductor?
A. Rubber
B. Glass
C. Copper
D. Wood
Answer: C. Copper
Rationale: Copper is widely used due to its excellent conductivity, ductility, and
durability. Insulating materials like rubber, glass, and wood resist electrical flow
and are not suitable as conductors.
Question 9
What is the purpose of a fuse in a circuit?
A. Regulate voltage
B. Protect against overcurrent by melting
C. Increase current flow
D. Store electrical energy
Answer: B. Protect against overcurrent by melting
