Electrical Systems & Wiring Flashcards

What is the maximum voltage drop percentage recommended by NEC for branch circuits?

Answer: 3%

NEC recommends (not mandates) no more than 3% voltage drop on branch circuits and 5% total including feeders for efficient operation.

What type of wire insulation is rated for use in wet locations and direct burial?

Answer: USE-2 or UF-B

USE-2 and UF-B (Underground Feeder) cables have moisture-resistant insulation approved for wet locations and direct earth burial.

What is the purpose of a transfer switch in a standby generator installation?

Answer: To prevent the generator and utility from being connected simultaneously

A transfer switch ensures that generator power and utility power are never connected together, preventing dangerous backfeed onto utility lines.

What does 'ampacity' mean in electrical wiring?

Answer: The maximum continuous current a conductor can carry without overheating

Ampacity is the maximum current a conductor can carry continuously under specific conditions before its insulation reaches its rated temperature limit.

Which type of lighting circuit requires a 3-way switch configuration?

Answer: A fixture controlled from two different locations

3-way switches allow a single light fixture to be turned on or off from two separate locations, such as both ends of a hallway.

What is the minimum burial depth for PVC conduit containing 120V residential branch circuit wiring per NEC?

Answer: 18 inches

NEC Table 300.5 requires PVC conduit with branch circuit wiring to be buried at least 18 inches deep (reduced to 12 inches under a concrete slab).

In AC circuits, what does 'power factor' measure?

Answer: How efficiently real power is used relative to apparent power

Power factor (PF = real power / apparent power) measures how effectively a load converts electrical energy into useful work; a PF of 1.0 is ideal.