Building Engineering Electrical Systems in Buildings

Question 1

What is the standard voltage for single-phase residential electrical service in the United States?

Accepted Answer

120/240V

Answer

US residential single-phase service delivers 120V for small appliances and 240V for large loads like dryers and ranges.

Question 2

Which wire color indicates a grounded neutral conductor in US electrical wiring?

Accepted Answer

White

Answer

Per NEC, white or gray insulation identifies the grounded neutral conductor in US branch circuits.

Question 3

What device automatically disconnects a circuit when current exceeds its rated ampacity?

Accepted Answer

Circuit breaker

Answer

A circuit breaker trips on overcurrent to protect wiring and equipment from heat damage.

Question 4

What does GFCI stand for in building electrical systems?

Accepted Answer

Ground Fault Circuit Interrupter

Answer

A Ground Fault Circuit Interrupter detects small current leakages to ground and shuts off power within milliseconds to prevent electrocution.

Question 5

What is the minimum clearance required between electrical panelboards and the floor per the NEC?

Accepted Answer

6 feet 6 inches

Answer

NEC requires a minimum headroom of 6 feet 6 inches in front of electrical equipment for safe working space.

Building Engineering Practice Test