Chapter 14 Quiz

Part A: Multiple Choice

1. You open an outlet box in a home built in 1935 and find wires with a rubber and cloth-braided insulation running separately (not in a cable jacket), supported by ceramic insulators stapled to the framing. This is:

a) BX armored cable — the metal sheath has corroded off b) Knob-and-tube wiring c) Early NM cable from the pre-plastic era d) Aluminum branch circuit wiring

2. Which wire gauge should be used on a 20-amp, 120V kitchen countertop outlet circuit?

a) 14-gauge copper b) 12-gauge copper c) 10-gauge copper d) 8-gauge copper

3. You find an outlet box containing wire that appears silver rather than copper-colored on a 15-amp circuit in a home built in 1969. The most important next step is:

a) Replace the outlet with a 20-amp device to handle the increased resistance of aluminum b) Have an electrician evaluate the circuit and use CO/ALR-rated devices or pig-tail with anti-oxidant compound c) Install a GFCI outlet to provide protection against the arcing risks of aluminum d) No action is needed — aluminum branch circuit wiring is equivalent to copper and has no special requirements

4. You are replacing an outlet in a bathroom. The new outlet should be:

a) A standard 15-amp outlet is fine; bathrooms have no special outlet requirements b) A 20-amp outlet (T-shaped slot) because bathroom circuits are required to be 20 amps c) A GFCI outlet, or a standard outlet if the circuit has GFCI protection upstream d) A GFCI outlet only if the bathroom is adjacent to a shower

5. An electrical junction box splice point is buried in a wall cavity with no cover plate because a previous owner drywalled over it. The required correction is:

a) No action is needed if the splice is a proper wire nut connection b) Cut open the wall, install a proper junction box, and either make the cover plate accessible or re-route wiring to eliminate the splice c) Spray foam the cavity around the splice to prevent fire spread d) Drill an access hole through the drywall and insert a plastic cover

6. A standard dimmer switch rated for incandescent bulbs is controlling LED bulbs in a ceiling fixture. The homeowner reports that the bulbs flicker at low dimmer settings and one bulb failed early. What is the likely cause?

a) The LED bulbs are defective and should be replaced with the same model b) The circuit is overloaded — LED bulbs draw too much current for the dimmer's rating c) The dimmer is incompatible with LED bulbs; an LED-rated dimmer is needed d) The wire gauge is incorrect for the dimmer switch load

7. The NEC's "box fill calculation" determines:

a) The maximum number of outlets permitted on a single circuit b) The required depth of a junction box based on wire gauge c) The maximum number of conductors and devices a box can contain based on cubic inch capacity d) The minimum distance between junction boxes in a circuit run

8. You are replacing a single-pole switch and photograph the wiring before disconnecting. There is one cable entering the box. The black wire is connected to one switch terminal and the white wire (which has been marked with black tape) is connected to the other terminal. This is:

a) Incorrect wiring — white wires must always be neutrals and cannot connect to a switch terminal b) A switch loop — the white wire is re-identified as a current-carrying conductor, which is code-compliant with the re-identification tape c) A three-way switch configuration wired incorrectly — a single-pole switch should not have both wires on the same cable d) Evidence of aluminum wiring — silver-coded wires use this configuration

9. Dave Kowalski wants to add circuits for a woodworking shop in a detached building. What is the correct process in most jurisdictions?

a) He can do all the work himself without any permits since it's an outbuilding and not the main house b) He should pull an electrical permit, hire a licensed electrician for the sub-panel and feeder installation, and can do some of the circuit rough-in work himself in coordination with the permit c) No permit is required for outbuilding electrical work in rural jurisdictions d) A licensed electrician must do all work — homeowners cannot perform any electrical work

10. Backstab (push-in) connections on outlets are considered inferior to screw terminal connections because:

a) They are not rated for 20-amp circuits and can only be used on 15-amp outlets b) They create unreliable connections that can loosen over time, leading to arcing and overheating c) They are illegal under current NEC and must always be replaced d) They only work with aluminum wiring, not copper

Part B: Short Answer

11. Explain the safety concern with knob-and-tube wiring that has been covered with blown-in attic insulation. Why does insulation make the situation worse, not better?

12. A homeowner is ready to replace an outlet. After turning off the circuit breaker and approaching the outlet with a non-contact voltage tester, the tester beeps — indicating voltage is still present at the outlet. What has likely happened, and what should the homeowner do?

13. Describe the GFCI outlet wiring correctly using LINE and LOAD terminals. Explain what happens when one GFCI outlet protects downstream outlets on the same circuit — and what the visual difference is between a protected outlet and an unprotected outlet in this configuration.

14. A homeowner wants to install a smart dimmer switch that requires a neutral wire. When they open the switch box, they find a switch loop: one cable with a black wire and a re-identified white wire (black tape), but no neutral. What are their two main options, and what are the tradeoffs?

15. List five warning signs at outlets or switches that indicate an electrical problem requiring attention. For each, describe what the sign suggests about what's happening inside the wall or device.

Answer Key

Part A

  1. b) Knob-and-tube wiring — K&T is characterized by individually run conductors (not bundled in a cable jacket), with ceramic knob supports and ceramic tube insulators through framing

  2. b) 12-gauge copper — Kitchen countertop circuits are required to be 20-amp circuits; 20-amp circuits require 12-gauge wire (14-gauge is rated only for 15-amp circuits)

  3. b) Have an electrician evaluate and use CO/ALR-rated devices or pig-tail — Aluminum branch circuit wiring requires specific corrective measures at all connection points; simply upgrading devices or adding GFCI doesn't address the core problem of aluminum-to-copper connections

  4. c) A GFCI outlet, or a standard outlet if protected upstream — Bathroom outlets must have GFCI protection; this can be provided by a GFCI outlet at each location or by a GFCI breaker or upstream GFCI outlet protecting the entire bathroom circuit

  5. b) Open the wall, install a proper junction box, make the cover accessible or re-route wiring — NEC 314.29 requires all junction boxes to be accessible without disturbing the building structure; burying a splice is a violation that must be corrected

  6. c) The dimmer is incompatible with LED bulbs — LED bulbs require LED-compatible dimmers; using an incandescent dimmer with LEDs commonly causes flickering, buzzing, reduced dimming range, and shortened bulb life

  7. c) The maximum conductors and devices a box can contain based on cubic inch capacity — Box fill calculations prevent overfilling boxes, which can damage insulation, cause poor connections, and create heat buildup

  8. b) A switch loop with correctly re-identified white wire — In a switch loop, the cable carries power down to the switch and switched power back; the white wire acts as a second hot and must be re-identified with black tape. This is code-compliant with the re-identification.

  9. b) Pull a permit, hire an electrician for sub-panel and feeder, do some circuit rough-in with permit — A sub-panel and feeder installation requires a permit in virtually all jurisdictions; some of the circuit rough-in work inside the shop may be done by the homeowner under the permit in many jurisdictions

  10. b) Backstab connections can loosen over time, leading to arcing and overheating — Backstab connections don't provide the mechanical clamp of a screw terminal; as connections loosen, resistance increases at the connection point, creating heat and eventually arcing

Part B (Model Answers)

11. Knob-and-tube wiring was designed to run in open air, where natural convection could carry away the heat generated by resistance in the wire. The spacing of individual conductors (run separately, not bundled) was specifically intended to allow heat dissipation. When blown-in attic insulation surrounds K&T wiring, it eliminates the air circulation that carries away this heat. The insulation traps heat against the wire and its already-aging rubber insulation, causing the insulation to degrade faster, become brittle, and crack. Cracked insulation on a wire that's running through or near wood framing creates a direct fire ignition risk. The insulation doesn't cool the wire — it makes the temperature problem worse, not better. This is one of the specific scenarios that most frequently drives insurance companies to decline coverage on homes with K&T wiring.

12. The most likely explanation is that the homeowner has turned off the wrong breaker — the outlet they're working on is on a different circuit than they believed. This is a real risk when panel directories are incomplete or inaccurate, which is common in older homes. The other possibility (less common but it happens) is that the box contains wires from more than one circuit, and the wires from the second circuit remain live even though the first circuit's breaker was turned off. The correct response: do not proceed. Identify which breaker actually controls this outlet (use a circuit breaker finder or the mapping method from Chapter 13), turn off that breaker, and re-test. If the outlet tests dead but other wires in the box still test live, identify those circuits and turn them off too before working in the box.

13. A GFCI outlet has two sets of terminals: LINE (where incoming power from the panel connects) and LOAD (where downstream outlets connect). The LINE terminals connect the black hot wire and white neutral wire from the supply cable. The LOAD terminals connect the black and white wires that continue to downstream outlets. The GFCI monitors the current balance at the LINE terminals; any imbalance of 5 milliamps or more triggers the GFCI to cut power to both the LINE-side outlet and all LOAD-side downstream outlets simultaneously. The visual difference: the GFCI outlet itself has TEST and RESET buttons. Downstream outlets protected through the LOAD terminals look like standard outlets (no buttons). When an outlet tester is plugged into a GFCI-protected downstream outlet, it may show "open ground" even if correctly wired — or on some testers, it may indicate "GFCI protected" if the tester has that capability. Many electricians attach "GFCI Protected" stickers (included in GFCI outlet packages) to the downstream outlets to identify them.

14. The homeowner has two main options. Option 1: Install a smart switch designed for "no-neutral" operation. Some smart switch manufacturers offer versions specifically designed to operate without a neutral wire. These typically work by drawing a tiny amount of current through the load (the light bulb) even when "off" — this can cause LEDs to glow faintly, limit dimming range, or be incompatible with some LED drivers. They work reasonably well with certain LED loads but not universally. The tradeoff is limited compatibility and potential performance issues. Option 2: Have an electrician run a neutral wire to the switch box. This is the clean, fully capable solution. How difficult it is depends on how the circuit is wired: if there's a junction box with a neutral wire nearby (in the attic or ceiling above), adding a cable to bring the neutral to the switch box may be straightforward; if the cable must be fished through finished walls, it can be labor-intensive. Cost varies from $100–$400+ depending on access. The tradeoff is cost and disruption vs. full smart switch capability with any LED or other load.

15. Five warning signs at outlets and switches: - Scorch marks or discoloration on the outlet face or cover plate: Indicates arcing or overheating inside the device or at its wiring connections. The hot gases from an arc can discolor the plastic cover. This is a fire risk that requires immediate attention — turn off the circuit and replace the device; also investigate the cause. - Outlet or switch plate warm to the touch: Normal outlets and switches should be at room temperature. Warmth indicates resistance at a connection — either a loose connection, a failing device, or an overloaded circuit. All three scenarios deserve investigation. - Outlet or switch that moves when used: Mechanical looseness suggests the mounting screws are loose, which often goes along with loose wiring connections. Loose connections are a leading cause of arcing and fire. Tighten the mounting, check the wire connections. - Buzzing or crackling sounds from an outlet, switch, or light fixture: Electrical sounds — buzzing, crackling, sizzling — almost always indicate arcing. This is the signature that AFCI protection is designed to detect and interrupt. Without AFCI protection, this arcing can ignite materials inside the wall. Turn off the circuit and call an electrician. - A persistent burning smell from a specific outlet or switch location: Burning plastic or ozone smell localized to a device or a section of wall indicates active overheating or arcing inside. This is an electrical emergency, not a "monitor it" situation. Turn off the circuit and call an electrician the same day.