Electromagnetic field (EMF) strength around cables is primarily influenced by current, not voltage. In a single-phase system, the live and neutral conductors are separated, creating a larger magnetic loop area. This produces stronger stray EMF when current increases.
In a balanced three-phase system, the magnetic fields from the three conductors largely cancel each other out, resulting in much lower net EMF, even at higher currents.
Therefore, the correct statement is that increasing current in single-phase cables produces higher EMF compared to three-phase cables. Options B, C, and D incorrectly link EMF to voltage or incorrect current behavior.
[References: IEEE Std 141 (Red Book – Power Distribution), IEC 61000-5-7 (EMF mitigation guidelines), ANSI/TIA-942-B §6.6., , ]
Question # 35
What should be considered when installing overhead data cabling?
Options:
A.
To maintain minimum separation from power and ensure that the fire detection and suppression systems are not hindered.
B.
Copper data cabling should not be placed in metal cable trays.
C.
Optical fiber cabling should always be positioned on top of the copper cabling in the same cable tray to avoid damage to the sensitive optical fiber.
D.
All cabling should make sharp bends directly into the rack to avoid usage of additional space and blocking the airflow on top of the rack.
When installing overhead data cabling, it’s crucial to maintain minimum separation from power cables to prevent electromagnetic interference. Additionally, cabling should be arranged so that it does not obstruct fire detection and suppression systems, allowing for proper sensor function and suppression agent dispersion in the event of a fire.
Detailed Explanation:
Separation between power and data cabling minimizes the risk of interference and helps ensure compliance with standards for signal integrity. Proper placement relative to fire suppression systems ensures that any smoke or heat can be effectively detected, and suppression agents can be evenly distributed without obstruction from cabling.
EPI Data Center Specialist References:
EPI guidelines emphasize maintaining adequate separation between power and data cables for safety and performance and ensuring cabling does not interfere with essential safety systems in data centers.
Question # 36
What is forced entry resistance based on?
Options:
A.
Time, tools, and people
B.
Rate and installed number of CCTV cameras
C.
Building materials used and the location of the data center
Perforated tiles should be located in front of equipment racks, aligned with cold aisles, to deliver supply air directly to server intakes. Best practice is one perforated tile per rack, adjusted based on airflow requirements and rack load.
Placing tiles at the back (A) disrupts airflow.
Spacing every 5th rack (B) provides insufficient cooling.
Placing near AC (D) causes uneven distribution and pressure loss.
Which gas-based system in general requires a larger amount of gas in order to be effective, a halocarbon gas-based fire suppression system or an inert gas-based fire suppression system?
Options:
A.
Inert gas requires a smaller amount of gas compared to halocarbon gas
B.
Inert gas requires a larger amount of gas compared to halocarbon gas
C.
Inert gas and halocarbon gas require the same amount of gas
D.
Impossible to answer without knowing the temperature
Inert gas systems (e.g., Inergen, Argonite, Nitrogen) extinguish fire by reducing oxygen concentration, which typically requires reducing oxygen levels to ~12–15%. This means a very large volume of gas must be discharged into the room (up to 40–50% of the protected volume). Because inert gases have a low extinguishing effectiveness by weight, more total gas is required.
Halocarbon agents (FM-200, Novec 1230) extinguish fire chemically by interrupting the combustion chain reaction. They require only a small percentage (6–9%) concentration in the room volume. As a result, the storage space for cylinders is much smaller compared to inert gas systems.
Therefore, inert gas systems generally require a larger gas volume to achieve extinguishing concentrations.
[References: NFPA 2001 §5.4 (Agent Quantities), ISO 14520-1 §5.3, EXIN DCS Study Guide – Fire Suppression., , ]
Question # 39
What is the advantage of using Multi-fiber Push-On (MPO) connectors?
Options:
A.
No advantage, cannot be used with OM4 fiber
B.
Allows a single connector with multiple fibers running parallel, enabling easy upgrade to 40–100 Gbit/s
C.
Made of high-quality materials, reusable without risk
D.
Very flexible, can be used for both copper and optical fiber
MPO connectors are multi-fiber connectors that support 12, 24, or more fibers in a single connector. Their key advantage is enabling parallel optics—where multiple fibers transmit simultaneously. This makes them ideal for 40GBASE-SR4 and 100GBASE-SR10 Ethernet links.
With OM4 or OM5 fiber, MPO cabling supports short-reach high-speed links in modern data centers.
Option A is incorrect; MPO works with OM3/OM4/OM5.
Option C is misleading; all connectors degrade with repeated use.
Option D is false because MPO is optical-only.
The real advantage is parallel multi-fiber transmission in one connector, simplifying cabling for high-speed networking.
