CEI Electrical System Components 2 — Questions and Answers
Question 1: What is the maximum voltage rating for a standard residential duplex receptacle installed in the US?
- 120V (Correct answer)
- 240V
- 277V
- 480V
Correct answer: 120V
Standard residential duplex receptacles are rated for 120V use in the US.
Question 2: Which component in a panelboard provides overcurrent protection for individual branch circuits?
- Main lugs
- Circuit breakers (Correct answer)
- Neutral bus bar
- Ground bus bar
Correct answer: Circuit breakers
Circuit breakers in a panelboard provide overcurrent protection by tripping when current exceeds rated capacity.
Question 3: A Type SE (service entrance) cable is primarily used for what application?
- Underground feeder runs
- Connecting service equipment to the utility (Correct answer)
- Interior branch circuit wiring
- Swimming pool bonding
Correct answer: Connecting service equipment to the utility
Type SE cable is designed for use as a service entrance conductor connecting service equipment to the utility supply.
Question 4: What does the term 'ampacity' refer to in electrical systems?
- The voltage rating of a conductor
- The current-carrying capacity of a conductor (Correct answer)
- The impedance of a circuit
- The power factor of a load
Correct answer: The current-carrying capacity of a conductor
Ampacity is the maximum current a conductor can carry continuously without exceeding its temperature rating.
Question 5: Which type of conduit is NOT suitable for direct burial without additional protection?
- Rigid metal conduit (RMC)
- Intermediate metal conduit (IMC)
- Electrical metallic tubing (EMT) (Correct answer)
- Rigid polyvinyl chloride conduit (PVC Schedule 40)
Correct answer: Electrical metallic tubing (EMT)
EMT is not listed for direct burial because its thin walls provide insufficient protection against soil corrosion and physical damage.
Question 6: In a three-phase, 4-wire wye system, what is the relationship between line voltage and phase voltage?
- Line voltage equals phase voltage
- Line voltage is 1.73 times phase voltage (Correct answer)
- Line voltage is 2 times phase voltage
- Line voltage is 0.577 times phase voltage
Correct answer: Line voltage is 1.73 times phase voltage
In a wye system, line voltage equals phase voltage multiplied by the square root of 3 (approximately 1.732).
Question 7: What is the purpose of an equipment grounding conductor (EGC) in a branch circuit?
- Carry normal load current
- Provide a low-impedance fault path to facilitate overcurrent device operation (Correct answer)
- Balance the load between phases
- Reduce harmonic distortion
Correct answer: Provide a low-impedance fault path to facilitate overcurrent device operation
The EGC provides a low-impedance return path for fault current so overcurrent devices will operate quickly and clear faults.
CEI Electrical System Components 2
What is the maximum voltage rating for a standard residential duplex receptacle installed in the US?