Electrical Systems & Wiring Flashcards

What is the minimum depth of burial required for UF (underground feeder) cable used for residential outdoor wiring per NEC?

Answer: 18 inches

NEC Table 300.5 requires UF cable to be buried a minimum of 24 inches, though 12 inches is allowed under certain conduit conditions.

In a 240V residential circuit for a dryer, what color combination of hot wires is used?

Answer: Black and red

240V circuits use two ungrounded (hot) conductors, typically black and red, each carrying 120V to neutral for a combined 240V.

What is the primary purpose of bonding in an electrical system?

Answer: Ensure all metal parts are at the same electrical potential to prevent shock

Bonding connects all metal components to maintain equal potential, so no dangerous voltage difference exists between touchable metal surfaces.

Which NEC article primarily governs wiring methods and materials for general use?

Answer: Article 300

NEC Article 300 covers general requirements for all wiring methods including installation, protection, and conductor fill.

What does a three-way switch circuit allow you to do?

Answer: Control a light from two different locations

A three-way switch configuration uses two switches and a traveler wire pair, allowing a light to be controlled from two separate locations.

What is 'voltage drop' and why is it significant in long wire runs?

Answer: The reduction in voltage along a conductor due to its resistance, reducing efficiency and device performance

Voltage drop occurs because wire resistance dissipates energy; NEC recommends keeping it below 3% for branch circuits to ensure proper device operation.

Which wiring method uses individual conductors pulled through metal or PVC tubing for protection?

Answer: Conduit wiring

Conduit wiring routes individual THHN or THWN conductors through EMT, IMC, or PVC conduit, offering superior physical protection and rewirability.