Free CEM Test Lighting Systems Questions and Answers — Questions and Answers
Question 1: An art gallery is upgrading its lighting to ensure the colors of the artwork are perceived as accurately as possible under artificial light. Which of the following lighting metrics is the most critical to consider for this application?
- Correlated Color Temperature (CCT)
- Luminous Efficacy (lm/W)
- Color Rendering Index (CRI) (Correct answer)
- Illuminance (foot-candles)
Correct answer: Color Rendering Index (CRI)
Color Rendering Index (CRI) measures a light source's ability to reveal the colors of objects faithfully in comparison with a natural light source. A high CRI (typically >90) is crucial in settings like art galleries, retail, and print shops where accurate color representation is essential.
Question 2: A 12-watt LED lamp produces a total of 1,620 lumens. What is the luminous efficacy of this lamp?
- 0.007 W/lumen
- 135 lumens/watt (Correct answer)
- 19,440 lumen-watts
- 150 watts
Correct answer: 135 lumens/watt
Luminous efficacy is the measure of how well a light source produces visible light, calculated as lumens divided by watts. In this case, 1,620 lumens / 12 watts = 135 lumens/watt (lm/W).
Question 3: A 10,000 square foot warehouse space is illuminated by 80 high-bay fixtures. Each fixture consumes a total of 150 watts (including the driver). What is the Lighting Power Density (LPD) for this space?
- 1.2 W/ft² (Correct answer)
- 0.83 W/ft²
- 1.5 W/ft²
- 12.0 W/ft²
Correct answer: 1.2 W/ft²
Lighting Power Density (LPD) is calculated by dividing the total power of the lighting system by the area it illuminates. Total Power = 80 fixtures * 150 W/fixture = 12,000 W. LPD = 12,000 W / 10,000 ft² = 1.2 W/ft².
Question 4: Which of the following light sources is generally characterized by the longest rated service life, often exceeding 50,000 hours?
- Metal Halide
- Incandescent
- Linear Fluorescent
- Solid-State Lighting (LED) (Correct answer)
Correct answer: Solid-State Lighting (LED)
Solid-State Lighting (LED) has the longest rated lifespan among common commercial light sources, frequently rated for 50,000 to 100,000 hours or more. This is significantly longer than fluorescent (10,000-20,000 hours), metal halide (6,000-15,000 hours), and incandescent (around 1,000 hours) lamps.
Question 5: A facility manager is implementing a lighting maintenance program for a large office building with thousands of fluorescent lamps. Which of the following is a primary advantage of a group relamping strategy over a spot relamping strategy?
- Maximizes the operational life of every individual lamp.
- Significantly lower upfront material cost.
- Requires less planning and specialized equipment.
- Reduced labor costs per lamp and more uniform light levels. (Correct answer)
Correct answer: Reduced labor costs per lamp and more uniform light levels.
Group relamping, where all lamps in an area are replaced at once, significantly reduces the labor time required per lamp compared to replacing them one by one as they fail. This scheduled approach also results in more consistent and uniform light levels across the facility, as all lamps are of a similar age and lumen output.
Question 6: In a large warehouse with high ceilings and aisles that have intermittent forklift and personnel traffic, which lighting control strategy would yield the highest energy savings while maintaining safety?
- A central timeclock shutting off all lights after business hours.
- Manual wall switches located at the end of each aisle.
- Networked luminaire-level controls with integrated occupancy and daylight sensors. (Correct answer)
- Photocells that turn lights on only when it is dark outside.
Correct answer: Networked luminaire-level controls with integrated occupancy and daylight sensors.
Networked luminaire-level controls allow for granular control, meaning each fixture or small group of fixtures can react independently. Integrated occupancy sensors will turn lights on in an aisle only when traffic is present and off when it is vacant. Daylight sensors can further dim the lights when sufficient natural light is available from skylights, maximizing energy savings without compromising safety.
Free CEM Test Lighting Systems Questions and Answers
An art gallery is upgrading its lighting to ensure the colors of the artwork are perceived as accurately as possible under artificial light.
Which of the following lighting metrics is the most critical to consider for this application?