LLC Material Selection & Properties 3 — Questions and Answers
Question 1: Which type of finish on brass fixtures provides the longest lifespan when exposed to acidic soil conditions?
- Lacquer coat
- Powder coat (Correct answer)
- Patina finish
- Anodized layer
Correct answer: Powder coat
Powder coating creates a thick, durable barrier that protects brass from acidic soil, outlasting lacquer and natural patina finishes.
Question 2: When comparing cast aluminum to die-cast zinc for fixture housings, which property favors cast aluminum in outdoor applications?
- Lower melting point
- Superior corrosion resistance (Correct answer)
- Higher density
- Lower material cost
Correct answer: Superior corrosion resistance
Cast aluminum forms a natural oxide layer that resists corrosion without additional coatings, while zinc is more susceptible to corrosive environments.
Question 3: Which wire insulation type is listed for direct burial without conduit in landscape lighting per NEC requirements?
- THHN
- UF-B (Correct answer)
- THWN
- NM-B
Correct answer: UF-B
UF-B (Underground Feeder) cable is specifically designed and listed for direct burial applications without requiring conduit protection.
Question 4: What property of copper makes it the preferred conductor material over aluminum for low-voltage landscape lighting connections?
- Higher tensile strength
- Lower resistance per unit length (Correct answer)
- Greater flexibility
- Lower cost per foot
Correct answer: Lower resistance per unit length
Copper has lower electrical resistance per unit length than aluminum, reducing voltage drop over long runs common in landscape lighting systems.
Question 5: For fixtures mounted on wood structures, which mounting material should be avoided due to accelerated corrosion from tannins?
- Stainless steel fasteners
- Aluminum screws
- Carbon steel fasteners (Correct answer)
- Silicon bronze screws
Correct answer: Carbon steel fasteners
Carbon steel fasteners corrode rapidly when exposed to tannins found in cedar and redwood, causing staining and structural failure.
Question 6: Which optical lens shape produces the widest spread pattern for ground-level area illumination in landscape lighting?
- Spot lens
- Flood lens
- Linear spread lens
- Asymmetric lens (Correct answer)
Correct answer: Asymmetric lens
An asymmetric lens distributes light in an uneven pattern that maximizes horizontal spread while controlling glare, ideal for ground-level area lighting.
Question 7: What characteristic of polyethylene conduit makes it preferable over rigid PVC conduit for direct-burial landscape lighting runs?
- Higher temperature rating
- Flexibility around obstacles (Correct answer)
- UV resistance
- Lower cost
Correct answer: Flexibility around obstacles
Flexible polyethylene conduit can be routed around tree roots, rocks, and curves without fittings, simplifying direct-burial installation.
LLC Material Selection & Properties 3
Which type of finish on brass fixtures provides the longest lifespan when exposed to acidic soil conditions?