Electrical Systems & Wiring Flashcards
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Read the first 7 Electrical Systems & Wiring flashcards as text
What is the NEC requirement for receptacle placement along walls in a habitable room?
Answer: Every 6 feet so no point is more than 6 feet from an outlet
NEC 210.52 requires receptacles so that no point along the wall is more than 6 feet from an outlet, measured horizontally.
Which type of electrical fault occurs when a hot wire contacts a neutral wire directly, bypassing the load?
Answer: Short circuit
A short circuit occurs when hot and neutral (or two hot conductors) make unintended contact, creating near-zero resistance and a massive current surge that trips the breaker.
What does the term 'service entrance' refer to in a residential electrical system?
Answer: The conductors and equipment that bring utility power from the meter to the main disconnect
The service entrance includes the service drop or lateral, meter base, and service entrance conductors that deliver utility power to the main disconnect.
What happens when a circuit breaker 'trips' due to an overload?
Answer: It opens the circuit to interrupt current flow, protecting the wiring from heat damage
When current exceeds the breaker's rating, a thermal-magnetic mechanism opens the contacts, stopping current flow before the wiring overheats.
What is the correct procedure for extending a circuit to add a new outlet?
Answer: Tap power from the nearest outlet box using properly sized wire and a new box
Extending a circuit means running new cable from an existing outlet box (pig-tailing connections) to a new box, ensuring the circuit's total load stays within the breaker rating.
Which grounding electrode is considered the most effective for residential grounding systems per NEC?
Answer: A driven ground rod (8-foot copper-clad rod)
NEC 250.52 lists acceptable grounding electrodes, and an 8-foot copper-clad ground rod driven into the earth is one of the most common and effective methods.
What does 'knob and tube' wiring lack that makes it potentially unsafe by modern standards?
Answer: A grounding conductor, limiting the ability to safely use modern grounded equipment
Knob and tube wiring has only two conductors (hot and neutral) with no ground wire, making it incompatible with modern three-prong devices and lacking fault protection.