ECS Electrical Wiring and Cable Installation 2 — Questions and Answers
Question 1: Which cable type is specifically rated for direct burial underground installation?
- NM-B (Romex)
- UF-B (Underground Feeder) (Correct answer)
- THHN in conduit only
- SJ flexible cord
Correct answer: UF-B (Underground Feeder)
UF-B cable is rated for direct underground burial because it has a moisture-resistant, sunlight-resistant outer jacket.
Question 2: Why are cables sometimes installed with armoring in electrotechnical work?
- To improve conductivity
- To protect against physical damage in industrial or hazardous environments (Correct answer)
- To reduce insulation thickness
- To allow higher voltage ratings
Correct answer: To protect against physical damage in industrial or hazardous environments
Armored cables (such as MC cable) have a metal sheath that protects the conductors from physical impact and abrasion in demanding environments.
Question 3: What is the purpose of cable trunking in an electrical installation?
- To increase cable current capacity
- To organize and protect multiple cables running along the same route (Correct answer)
- To waterproof outdoor cabling
- To reduce electromagnetic interference between circuits
Correct answer: To organize and protect multiple cables running along the same route
Cable trunking provides an organized raceway that protects, contains, and routes multiple cables neatly through a building.
Question 4: How should cables be identified in a multi-circuit electrical installation?
- By their length only
- Using color-coded insulation and circuit labels or tags (Correct answer)
- By the manufacturer's brand markings
- Identification is not required if conduit is used
Correct answer: Using color-coded insulation and circuit labels or tags
Cables must be identified using standardized color codes and circuit labeling so that any electrician can safely identify circuits during maintenance.
Question 5: What is the function of a cable gland in an electrical installation?
- To amplify the signal in data cables
- To provide a secure, sealed entry point where a cable enters an enclosure (Correct answer)
- To increase the current rating of a cable
- To splice two cables together underground
Correct answer: To provide a secure, sealed entry point where a cable enters an enclosure
A cable gland clamps onto the cable sheath to provide strain relief and an IP-rated seal at the point where the cable enters a junction box or panel.
Question 6: What does the term 'diversity factor' mean in electrical installation design?
- The variety of cable sizes on a project
- The assumption that not all loads will operate simultaneously, allowing smaller supply cables (Correct answer)
- The ratio of AC to DC circuits in a building
- The number of different voltage levels in a system
Correct answer: The assumption that not all loads will operate simultaneously, allowing smaller supply cables
Diversity factor recognizes that all connected loads rarely operate at full power simultaneously, allowing the supply circuit to be sized below the sum of all individual load ratings.
ECS Electrical Wiring and Cable Installation 2
Which cable type is specifically rated for direct burial underground installation?