Electrician Services and Distribution 2 — Questions and Answers
Question 1: What is a 'panelboard' as defined by the NEC?
- A large switchboard used only in commercial buildings
- A single- or poly-phase unit for controlling circuits by means of overcurrent devices (Correct answer)
- A meter base assembly provided by the utility
- A transformer vault enclosure
Correct answer: A single- or poly-phase unit for controlling circuits by means of overcurrent devices
A panelboard is a distribution assembly containing overcurrent protective devices and buses that distribute power to branch circuits.
Question 2: What happens when a circuit breaker trips?
- It permanently disconnects the circuit
- It increases the resistance in the circuit
- It automatically opens the circuit to interrupt overcurrent (Correct answer)
- It reduces voltage to the circuit
Correct answer: It automatically opens the circuit to interrupt overcurrent
A circuit breaker automatically opens to interrupt current flow when it detects an overload or short circuit condition.
Question 3: What is the purpose of a transfer switch in an electrical system?
- To convert DC power to AC power
- To transfer load between two power sources such as utility and generator (Correct answer)
- To step up voltage for distribution
- To measure and monitor power quality
Correct answer: To transfer load between two power sources such as utility and generator
A transfer switch safely switches electrical loads from the utility supply to a generator or alternate power source.
Question 4: What size copper conductor is typically required for a 100-amp service entrance?
- 4 AWG
- 2 AWG (Correct answer)
- 1/0 AWG
- 2/0 AWG
Correct answer: 2 AWG
A 100-ampere service typically requires 2 AWG copper service entrance conductors per NEC Table 310.16.
Question 5: What is the purpose of a neutral bar in a main electrical panel?
- To connect all hot conductors
- To provide a common connection point for grounded (neutral) conductors (Correct answer)
- To bond the panel to the building structure
- To distribute 240V circuits
Correct answer: To provide a common connection point for grounded (neutral) conductors
The neutral bar provides a terminal block where all grounded (neutral) conductors connect to complete the circuit back to the source.
Question 6: Per the NEC, where must the grounding electrode conductor connect to a ground rod?
- At the top of the rod only
- Within the first 12 inches of the top (Correct answer)
- Anywhere along the rod
- Only at the midpoint
Correct answer: Within the first 12 inches of the top
The grounding electrode conductor must be connected within the upper 12 inches (top) of the ground rod per NEC 250.70.
Electrician Services and Distribution 2
What is a 'panelboard' as defined by the NEC?