Material Selection & Properties Flashcards

Which insulation material is most commonly used on wiring inside alarm control panels due to its flame-retardant properties?

Answer: PVC (polyvinyl chloride)

PVC insulation is standard in alarm control panels because it is inherently flame-retardant and resists moisture.

When selecting wire for a buried outdoor loop detector circuit, which material property is most critical?

Answer: Direct burial-rated jacket with moisture resistance

Buried wiring must have a direct burial-rated jacket that resists moisture, soil chemicals, and physical abrasion.

A technician needs conduit for an installation passing through a corrosive chemical storage area. Which material is the best choice?

Answer: PVC Schedule 40 conduit

PVC conduit is chemically inert and will not corrode in environments with harsh chemicals.

What is the primary reason THWN wire is preferred over THW wire for wet-location conduit runs?

Answer: THWN has a nylon outer jacket that resists moisture and pulling abrasion

The 'N' in THWN stands for nylon, which adds a tough outer jacket suitable for wet locations and easier conduit pulling.

Which conductor material has the highest electrical conductivity per unit cross-section?

Answer: Copper

Copper has higher electrical conductivity than aluminum, steel, or coated variants, making it the preferred conductor in alarm wiring.

A motion detector mounting surface is a metal HVAC duct that vibrates. Which mounting hardware material best minimizes false alarms caused by vibration transmission?

Answer: Rubber-grommet isolation mounts

Rubber-grommet isolation mounts absorb vibration, preventing mechanical movement from being transferred to the detector.

For a fire alarm initiating device circuit (IDC) run in a plenum ceiling, the cable jacket must be rated as:

Answer: CMP (Plenum)

CMP-rated (Plenum) cable is required in air-handling spaces because it produces minimal smoke and toxic gases if burned.