### What period was Knob-and-Tube wiring commonly used in North American homes? - [ ] 1920s to 1950s - [ ] 1940s to 1960s - [x] 1880s to 1930s - [ ] 1950s to 1970s > **Explanation:** Knob-and-tube wiring was a common electrical system used in North American homes and commercial buildings from the 1880s to the 1930s. It has since been replaced by more modern electrical systems that meet current safety and demand standards. ### What is a prominent safety concern associated with knob-and-tube wiring? - [ ] High cost of installation - [ ] Aesthetic appearance - [x] Lack of a grounding conductor - [ ] Difficult maintenance > **Explanation:** One of the major safety concerns with knob-and-tube wiring is the absence of a grounding conductor, which can increase the risk of electrical shock and fires. Modern electrical systems include grounding conductors to enhance safety. ### What was used in knob-and-tube wiring to protect circuits? - [ ] Metal tubes and boxes - [ ] Rubber insulation - [ ] Plastic covers - [x] Porcelain insulators and tubes > **Explanation:** Knob-and-tube wiring used porcelain insulators and tubes to protect circuits, particularly where wiring passed through joists or wall cavities. This method was necessary due to the lack of rubber insulation sleeves around the copper wires. ### Why has knob-and-tube wiring been mostly replaced in modern electrical installations? - [x] It does not meet current safety and demand standards - [ ] It is too expensive to maintain - [ ] It doesn't support high-voltage appliances - [ ] It requires frequent maintenance > **Explanation:** Knob-and-tube wiring has largely been replaced because it does not meet current safety and demand standards. Its lack of grounding conductors, improper confining of electrical switching, and potential for exposed wires make it unsuitable for today's home electrical requirements. ### Which modern feature is lacking in knob-and-tube wiring? - [ ] Flexible wiring - [x] Grounding conductor - [ ] Multiple circuit breakers - [ ] Energy efficiency > **Explanation:** A significant feature lacking in the knob-and-tube wiring system is a grounding conductor, which is crucial for minimizing the risk of electrical shocks and fire hazards. Modern systems incorporate grounding conductors for improved safety. ### In which American national guideline is knob-and-tube wiring only recommended for certain installations? - [ ] American Electrical Code (AEC) - [ ] International Residential Code (IRC) - [x] National Electric Code (NEC) - [ ] National Safety Code (NSC) > **Explanation:** The National Electric Code (NEC) only recommends knob-and-tube wiring for certain installations, recognizing the limitations and potential safety issues relative to modern electrical demands. ### How were wires typically insulated in knob-and-tube wiring? - [ ] Rubber insulation sleeves - [x] Not typically insulated - [ ] Plastic coatings - [ ] Metal sheathing > **Explanation:** In knob-and-tube wiring, most wires did not have rubber insulation sleeves around the copper cables. Instead, insulation was provided through the use of porcelain insulators and tubes. ### Which component is commonly missing or less utilized in knob-and-tube wiring, increasing the risk of circuits being exposed? - [ ] Fuses - [ ] Circuit breakers - [x] Junction boxes - [ ] Insulating tape > **Explanation:** In knob-and-tube wiring, junction boxes were not always used, leading to increased risks of circuits being exposed. This can be dangerous as it heightens the potential for electrical shock or fire. ### What main material was used for insulators in knob-and-tube wiring? - [x] Porcelain - [ ] Rubber - [ ] Plastic - [ ] Wood > **Explanation:** Porcelain was the main material used for insulators in knob-and-tube wiring. This material was essential for safely passing wires through joists and wall cavities while preventing direct contact that could cause short circuits.