CAT Material Selection & Properties 3 — Questions and Answers
Question 1: Which property of a material describes its ability to return to its original shape after being bent or stretched?
- Plasticity
- Elasticity (Correct answer)
- Ductility
- Malleability
Correct answer: Elasticity
Elasticity is the material property that allows it to recover its original dimensions after deformation.
Question 2: A technician is installing a glass-break sensor on a framed picture window. Which glass type will produce the most reliable frequency signature for detection?
- Laminated safety glass
- Tempered glass
- Annealed (float) glass (Correct answer)
- Wired glass
Correct answer: Annealed (float) glass
Annealed (float) glass shatters into large shards producing the classic high-frequency flex-and-break signature that glass-break sensors are tuned to detect.
Question 3: What does the 'mil' unit measure when specifying wire insulation thickness?
- Millimeters
- Thousandths of an inch (Correct answer)
- Milliamperes
- Millisiemens
Correct answer: Thousandths of an inch
One mil equals one thousandth of an inch (0.001"), a standard unit for measuring insulation and jacket thickness.
Question 4: When splicing alarm wiring in an outdoor junction box, which material should be used to protect splice connections from moisture?
- Standard twist-on wire nuts
- Silicone-filled (waterproof) wire nuts or gel-filled connectors (Correct answer)
- Bare copper crimp sleeves
- Electrical tape only
Correct answer: Silicone-filled (waterproof) wire nuts or gel-filled connectors
Silicone or gel-filled connectors seal out moisture at the conductor interface, preventing corrosion and resistance changes outdoors.
Question 5: A UL-listed alarm system requires end-of-line resistors. Which resistor body material provides the best long-term stability against temperature-induced value drift?
- Carbon composition
- Carbon film
- Metal film (Correct answer)
- Wire-wound
Correct answer: Metal film
Metal film resistors have low temperature coefficients and excellent stability over time compared to carbon composition or carbon film types.
Question 6: A technician selects a polycarbonate enclosure for an outdoor alarm keypad. What is the key advantage of polycarbonate over ABS plastic in this application?
- Lower cost
- Superior impact resistance and UV stability (Correct answer)
- Better electrical conductivity
- Lighter weight
Correct answer: Superior impact resistance and UV stability
Polycarbonate is significantly more impact-resistant and UV-stable than ABS, making it suitable for demanding outdoor environments.
Question 7: Which wire gauge has the largest physical diameter?
- 22 AWG
- 18 AWG
- 14 AWG
- 12 AWG (Correct answer)
Correct answer: 12 AWG
In the American Wire Gauge (AWG) system, a lower number indicates a larger diameter wire with greater current-carrying capacity.
CAT Material Selection & Properties 3
Which property of a material describes its ability to return to its original shape after being bent or stretched?