CDCP MCQ 4 — Questions and Answers
Question 1: What is the primary advantage of using lithium-ion batteries over VRLA batteries in a data centre UPS?
- Lower initial purchase cost
- Longer lifespan and higher energy density with smaller footprint (Correct answer)
- Greater tolerance for deep discharge cycles
- Simpler charging circuitry requirements
Correct answer: Longer lifespan and higher energy density with smaller footprint
Lithium-ion batteries offer 2–3x longer service life, higher energy density, and significantly smaller footprint compared to VRLA alternatives.
Question 2: In data centre physical security, what is a mantrap (or airlock)?
- An alarm system triggered by unauthorized server access
- A small room with two interlocking doors where only one can open at a time (Correct answer)
- A motion-sensor grid covering the data hall floor
- A biometric scanner that identifies personnel by gait
Correct answer: A small room with two interlocking doors where only one can open at a time
A mantrap is a physical security vestibule with two doors where the first must close before the second opens, preventing tailgating.
Question 3: Which power factor value indicates that all electrical power drawn from the utility is being converted to useful work with no reactive component?
- 0.0
- 0.5
- 0.8
- 1.0 (Correct answer)
Correct answer: 1.0
A power factor of 1.0 (unity) means all apparent power (kVA) equals real power (kW) with zero reactive power wasted.
Question 4: What does the term 'stranded capacity' refer to in data centre operations?
- Power or cooling capacity that cannot be used due to imbalances or constraints (Correct answer)
- Backup capacity held in reserve for disaster recovery
- Network bandwidth reserved for storage replication
- Floor space permanently allocated to decommissioned equipment
Correct answer: Power or cooling capacity that cannot be used due to imbalances or constraints
Stranded capacity occurs when power or cooling limits are reached in one dimension while capacity remains available in another, preventing full utilization.
Question 5: In hot aisle/cold aisle arrangements, which direction do server fans typically push airflow?
- From hot aisle to cold aisle (front to back)
- From cold aisle to hot aisle (front to back) (Correct answer)
- From top to bottom (vertical exhaust)
- From side to side (lateral exhaust)
Correct answer: From cold aisle to hot aisle (front to back)
Servers draw cool air in from the cold aisle (front) and exhaust hot air out the rear into the hot aisle.
Question 6: What is the role of a transfer switch (ATS/STS) in data centre power infrastructure?
- Converting AC power to DC for server power supplies
- Automatically switching the load between two power sources upon failure (Correct answer)
- Regulating voltage fluctuations from the utility grid
- Distributing power from a single source to multiple circuits
Correct answer: Automatically switching the load between two power sources upon failure
An Automatic/Static Transfer Switch (ATS/STS) monitors both power feeds and transfers the load to the alternate source within milliseconds if the primary fails.
Question 7: Which environmental monitoring parameter is most critical to prevent electrostatic discharge (ESD) damage in a data centre?
- Temperature
- Relative humidity (Correct answer)
- Airborne particulate count
- CO2 concentration
Correct answer: Relative humidity
Low relative humidity increases static electricity buildup; ASHRAE recommends maintaining humidity above a dew point of 41.9°F (5.5°C) to control ESD risk.
CDCP MCQ 4
What is the primary advantage of using lithium-ion batteries over VRLA batteries in a data centre UPS?